This review aims to describe the incidence of sports-related SCA, as well as its major causes. Also discussed are the sports paradox, and the potential advantages of experiencing SCA in a sports venue. The overwhelming benefits of exercise will be highlighted, including a brief review of the current recommendations.

Exercise-associated SCA is defined as occurring during or within one hour of physical activity. In North America and Europe, the overall incidence of SCA ranges from 500 to 1000 per million per year in the general population^1-3, and varies with age, gender, race, and underlying medical problems. The percentage of those events occurring during sports is less than six percent (see Table 1).^4-6 The most recent analysis of ‘The Oregon Sudden Unexpected Death Study (OUDS),’ a large, prospective, community-based study of out-of-hospital SCA, reports that between 2002−2013, SCA during sports accounted for five percent of all SCA, yielding an annual incidence of sports-related SCA in the middle-aged of approximately 22 per million per year, compared to 555 per million per year non sports-related SCA.⁶

In the recent Marijon study, Sudden Cardiac Arrest During Sports Activity in Middle Age, jogging or running activities accounted for over 25% of sports-related SCA, underscoring the popularity of this activity as a form of exercise. Participation in endurance sports such as running is constantly growing, and the number of participants has been increasing steadily over the past 15 years. Of the approximately 20 million participants in foot races in the United States annually, 54% are older than 35 years of age, and 57% are male (see Figure 1).⁸

Between 1990 and 2013, the number of participating athletes who completed running races in the United States increased significantly to 20 million per year; 54% were older than 65 years of age, and 57% were male.

In comparison, the incidence of SCAs among half-marathon and marathon participants is estimated to be 5 to 20 per million runners.⁹ Somewhat surprisingly, the incidence of exercise-associated SCA in middle age (22 per million per year) is similar to athletes participating in the National Collegiate Athletic Association (NCAA) sports (18.6 per one million, per athlete year).¹⁰Importantly, other serious non-cardiac events, such as heat stroke, are increasingly recognized as a greater risk to long distance runners than SCA.¹¹

Overwhelmingly, the majority of sports-related SCAs have occurred in men.^4-7,9-10 Potential explanations include historically lower participation rates for women in marathons or similar events, the fact that women tend to develop atherosclerosis on average 10 years later than men, gender differences related to atherosclerotic plaque morphology, ventricular electrical activity, and autonomic factors.

Current data strongly support a transient rise in incidence of SCA and acute myocardial infarction (AMI) during strenuous exercise.^12-14 However, regular habitual exercise mitigates that risk. A retrospective analysis of 133 cases of SCA among people without known heart disease revealed that the relative risk of SCA with exercise was inversely related to the habitual exercise level.¹² The relative risk of SCA among sedentary people was 56-fold higher during exercise. In contrast, the relative risk was significantly lower among men with the highest level of habitual vigorous activity. Additionally, despite the residual five-fold increased risk of SCA during vigorous activity, men with the highest habitual level of physical activity had a substantially lower relative risk (40% lower) of global SCA compared with sedentary controls.

Heavy physical exertion can trigger the onset of AMI, particularly in people who are typically sedentary.¹³ This association was evaluated among 1,228 confirmed cases of AMI. The incidence of AMI within one hour of strenuous physical activity (Six METs and above) was 4.4%. The relative risk was 50-fold higher among sedentary (exercise less than once per week) persons than those who exercised regularly (more than five times per week), as compared to those with less strenuous or no physical exertion.

The Physicians Health Study¹⁴ showed very similar findings. The overall relative risk of SCA within 30 minutes of vigorous exercise was ~17, and varied with frequency of exercise per week. The relative risk was 74-fold for those who exercised less than once per week and 11-fold for those who exercised fewer than times per week.

While existence of a “sports paradox” (vigorous activity that acutely and transiently increases the risk of SCA and AMI) has been recognized, especially in those not habituated to exercise, overall, the long-term benefits outweigh the short-term risks related to physical activity. As a colleague says, “If you survive exercise, which you almost certainly will, you will undoubtedly live longer and healthier.”

Coronary artery disease (CAD), whether previously unsuspected or already established, remains the most common etiology (80% to 84%) for SCA in middle age population.^6,15 Other, less common causes of sports-related SCA include hypertrophic cardiomyopathy, dilated cardiomyopathy, myocarditis, arrhythmogenic right ventricular dysplasia, valvular heart disease, and a small but distinct subgroup of unexplained SCA.^6,8,15 Importantly, 36% of patients who suffered SCA in the Oregon-OUDS⁶ study reported typical cardiovascular (CV) symptoms during the week preceding SCA, and 56% had at least one CV risk factor.

Although the risk of SCA is transiently increased during vigorous exercise, habitual vigorous exercise is associated with an overall lower risk of SCA.^13,14 The single greatest determinant of survival for victims of SCA is the time from collapse to defibrillation. Advanced life support in the field increases the likelihood of survival in cardiac arrest. This association has prompted both voluntary and compulsory placement of automated external defibrillators (AEDs) in exercise facilities.

Bystander cardiopulmonary resuscitation (CPR) and initial use of cardiac defibrillation are the strongest independent predictors for survival to hospital discharge among sports-related SCA patients.⁹ Sports-related SCA is more likely to be a witnessed event, suffer ventricular fibrillation, receive timely CPR and have higher survival to hospital discharge.⁶ Survival following SCA has been greatly improved by lay rescuer and public access defibrillation programs designed to shorten the time interval from SCA to shock delivery. Rapid defibrillation in public settings such as casinos, airlines, and airports has led to survival rates ranging from 41% to 74%, if bystander CPR was provided and defibrillation occurred within three to five minutes of collapse.^16,17

SCA occurring at a sports venue may improve chances for survival. A recent retrospective analysis reported better survival rate among the SCA victims at exercise sites where AEDs are available than at non-exercise indoor sites (56% vs. 34%; p < 0.001).¹⁸ Early CPR and defibrillation with an AED in youth experiencing SCA can result in a survival rate of 64% to 74%.¹⁹ A 2-year prospective study in 2,149 high schools indicated that 87% of participating schools had an onsite AED program. At these schools with an onsite program, 89% of students and adults who developed SCA during sports or physical activity survived to hospital discharge.²⁰ The survival rate for commotio cordis in young athletes has increased to 58% in the past few years, largely due to increased recognition, greater availability of AEDs, and early defibrillation.²¹

Thus, early CPR, defibrillation, and onsite AED programs are both critical and effective in maximizing survival following SCA. Continued expansion of these programs, including AED placement throughout running courses to enable rapid defibrillation of competitors, is recommended.

Exercise plays a primary role in preventing chronic disease and in maintaining health throughout life. The incidence of sports-related SCAs is surprisingly modest, and the long-term CV benefits of exercise clearly outweigh the risks. In previously sedentary healthy adults, both lifestyle and physical activity intervention, including a structured exercise program, improve exercise tolerance, cardiorespiratory fitness, and blood pressure.²² Regular exercise has well-established long-term benefits on CV health including: 1) lower total and low-density lipoprotein (LDL) cholesterol levels, higher high-density lipoprotein (HDL) cholesterol levels, and lower triglyceride levels; 2) lower incidence of systemic hypertension; 3) beneficial effects on both glucose metabolism and insulin sensitivity; 4) improved glycemic control, reduced visceral adipose tissue and plasma triglycerides in people with type 2 diabetes mellitus, even without weight loss.²³

There is an inverse relationship between physical activity and risk of CAD, which is the most common etiology for sports-related SCA. Regular aerobic exercise, both directly and indirectly, results in lower risk for developing CAD. The least fit men and women have an increased risk of death from CAD or cardiovascular diseases (CVD) compared with fit individuals.

Given the extensive CV benefit of exercise, a minimum of 30 minutes of moderate-intensity physical activity (continuous or in 10-minute increments), preferably most days of the week, is recommended. This is equivalent to roughly 1.5 miles/day of brisk walking. Even 15 minutes per day or 90 minutes per week is associated with a survival benefit compared with physical inactivity.²³

Keywords: Adolescent, Adult, Arrhythmogenic Right Ventricular Dysplasia, Atherosclerosis, Athletes, Blood Pressure, Cardiomyopathy, Dilated, Cardiomyopathy, Hypertrophic, Cardiopulmonary Resuscitation, Cholesterol, Cholesterol, Commotio Cordis, Coronary Artery Disease, Death, Sudden, Cardiac, Defibrillators, Diabetes Mellitus, Type 2, Exercise, Exercise Tolerance, Glucose, Heart Valve Diseases, Heat Stroke, Hypertension, Incidence, Insulin Resistance, Intra-Abdominal Fat, Jogging, Lipoproteins, HDL, Lipoproteins, LDL, Middle Aged, Myocardial Infarction, Myocarditis, Physical Exertion, Plaque, Atherosclerotic, Prevalence, Prospective Studies, Retrospective Studies, Risk, Risk Factors, Running, Sports, Survival Rate, Triglycerides, Ventricular Fibrillation, Walking, Weight Loss

Exercise is good for you, but some extreme athletes can push past healthy limits.

A research paper showed that some endurance athletes who exercised at very high intensity over long periods of time have higher rates of heart problems than people who exercise more moderately.

This new analysis of existing studies found that chronic extreme exercise training and competing in endurance events can lead to heart damage and rhythm disorders. People with genetic risk factors are especially vulnerable.

That doesn’t mean you should put away the walking shoes, though. Moderate exercise is still the best prescription for good physical and mental health – and competitive athletes shouldn’t give up their training schedule just yet.

Extreme athletes share determination, maybe risk

Unlike weekend warriors, brisk walkers or even enthusiastic joggers, extreme athletes regularly live up to their name, pushing the limits of their physical capabilities. They run 50 miles or more or repeat marathons in rapid succession, regularly pushing past exhaustion, dehydration and pain that would sideline or hospitalize many people.

[Tweet “#Exercise is good for your #heart, but #extremeathletes can push past healthy limits”]All extreme athletes share a steely determination. However, this paper asks, can too much of that determination and grit hurt your heart? The analysis at the Mid America Heart Institute looked at the relative heart health of extreme athletes as compared with that of others who exercised regularly, but with less intensity and frequency.

Results of review

In addition to the Mid America study findings, research published in the European Heart Journal found evidence that elite cross country skiers increased their risk for heart arrhythmias when they skied longer and faster.

The overall findings suggest that repeated grueling workouts stress the heart muscle — not just the skeletal muscles — and that chronic damage can lead to heart troubles.

What is behind the heart risks

Extreme, long-term endurance exercise puts equally extreme demands on the cardiovascular system. Experts found that after finishing extreme running events, athletes’ blood samples contain biomarkers associated with heart damage.

These ‘damage indicators’ usually go away by themselves, but when the heart endures extreme physical stress over and over, the “temporary” damage may lead to so called “remodeling” of the heart or physical changes such as thicker heart walls and scarring of the heart. This can also increase the risk of heart rhythm disorders, particularly for the minority who have underlying cardiac problems such as hypertrophic cardiomyopathy or coronary heart disease.

What this means for you

Dermot Phelan, MD,PhD, Director, Sports Cardiology Centerat Cleveland Clinic, did not participate in the analysis, but reviewed it and states that care should be taken in interpreting these results.

“Exercise and even strenuous exercise is clearly associated with enormous heart health benefits in the vast majority of people when compared to people who do not exercise but, in a very small minority who have underlying problems, exercise can trigger arrhythmia,” he says. “While there is emerging evidence that prolonged strenuous exercise can increase risk of atrial fibrillation, the long-term risk of this is small compared to inactivity.”

Proven benefits of regular exercise include lower blood pressure, increased strength, diabetes reduction risk and better mental health.

All in all, despite the concern about extreme exercise, there is not much reason for the average person to worry, Dr. Phelan says. “Exercising is far better than being inactive.”

Exercise guidelines

Experts agree that whether you are a sports enthusiast, a beginner, a senior or someone beginning cardiac rehab, physical activity is good for you. For the general public, The American Heart Association recommends a minimum of 150 minutes of moderate physical activity per week.

Moderate exercise includes activities such as walking, jogging or swimming. In general, moderate activities should leave you free to carry on a conversation while you are active. If you have symptoms, a history of a heart condition or risk factors for heart disease, check with your doctor before starting or changing an exercise regimen.

For those who are athletes and have new symptoms or a diagnosis of heart disease, or those who may be concerned about continuing competition or endurance sports, you should be evaluated by a sports cardiologist.

Athlete Charles “Chuck” Hughes was born on March 2, 1943. His tragic death left us a legacy we can learn from. He was a tremendous college football athlete at Texas Western College, now known as The University of Texas at El Paso (UTEP). He still holds many team records, including the most all-purpose yards in a single game (4-1), and the most receptions in a single game (17). In 2006, he was inducted into the UTEP Hall of Fame.

The Philadelphia Eagles drafted him into the NFL in 1967. After three seasons, he was traded to the Detroit Lions. But on October 24, 1971, he was jogging back to the huddle after a routine pass route, in which he was not targeted, when he suddenly collapsed on the field. Three plays earlier, he’d made a clutch 32-yard reception to sustain a Lions’ drive with just minutes left in the game. The Bears’ famed linebacker, Dick Butkus, was first to reach Hughes on the field and urgently alerted the Lions’ bench. Despite attempts at cardiopulmonary resuscitation, he died on the field. The game was finished in complete silence.

He remains the only NFL player to die on the field during a game. Hughes had a family history of heart disease, and an autopsy disclosed he had severe coronary atherosclerosis and had died of a heart attack. Six weeks before his death, Hughes had been hospitalized due to chest pain after a preseason game. Unfortunately, during that hospital admission, the doctors did not discover he had already developed severe coronary atherosclerosis: a blockage of the arteries by plaque build-up. They believed his pain probably came from an enlarged kidney, liver, or spleen, as Les Carpenter reported in December 2013 for Yahoo Sports.

Cardiac Arrest Is More Common as Athletes Age

Sudden cardiac arrest among young competitive athletes generates tremendous alarm, fear, and calls for action in our society. I am grateful for these responses, as they raise awareness of rare but potentially fatal heart conditions. They also prompt athletic venues and school systems to have emergency resuscitation equipment immediately available at all events. Fortunately, these events are rare among young people.

Unfortunately, cardiac arrest is more common as athletic competitors reach middle age, when age-related heart disease and heart disease risk factors develop. This may have prompted some of the sports writers who discussed Hughes’ heart to say that he had the heart of a 40-year-old man.

Risk of Sudden Cardiac Death Between Ages 35 and 65

The truth is that although more heart events occur in athletes during middle age, we don’t know a lot about these events, and we also don’t know ways to lower the rate or reduce the risk. Fortunately, a recent study by a team of renowned cardiac arrest investigators led by Sumeet Chugh, MD, at Cedars-Sinai Medical Center in Los Angeles, has improved our understanding of cardiac death in middle-aged sports participants.

The investigators looked into 1,247 sudden cardiac arrests in middle-aged people (average age 51) and then specifically looked at those that occurred during athletic participation. Nearly two-thirds of the arrests occurred from 6 a.m. to 6 p.m.; the most common time of arrest was between noon and 6 p.m. The two most common seasons for arrest were spring and summer.

The activities during which the arrests occurred were:

Jogging: 27 percent
Basketball: 17 percent
Cycling: 14 percent
Gym activities: 11 percent
Golf: 8 percent
Volleyball, tennis, and soccer: 3 percent each
Other activities: 14 percent

Among the athletic participants, 16 percent had a prior history of heart disease. Coronary artery disease, such as that found in Hughes, was previously known in 8 percent of the participants. Another 5 percent had a history of atrial fibrillation. Risk factors for heart disease were common: 40 percent had a history of high blood pressure, 31 percent had a smoking history, and 33 percent had high cholesterol.

When the authors looked at all cardiac arrests among middle-aged people, risk factors for heart disease were similar among those who died during athletics and those who did not. But the athletes were much less likely to have known heart disease or a prior history of heart disease. Sixteen percent of the athletes had a known history of heart disease compared to nearly double (30 percent) of middle-aged people who had a cardiac event in circumstances other than athletic participation.

Resuscitation of cardiac arrest remains a challenge today, and most people die. Only 23 percent of the middle-aged cardiac arrest victims who suffered during athletic activities lived. This survival rate is better than that for those who suffered from cardiac arrest during non-athletic activities (14 percent) — a rate probably due to the fact that someone noticed cardiac arrest in 87 percent of people who suffered during a sports activity, and possibly performed CPR.

Warning Signs a Week Before Cardiac Arrest During Sports

The most common cause of cardiac arrest was severe coronary artery disease similar to what Hughes had. In the Cedars-Sinai study, 84 percent had coronary artery disease. In approximately one-third of the victims, the arrest was from an acute myocardial infarction (heart attack) or a clot that had formed in the coronary arteries. The other two-thirds of the arrest victims had advanced narrowing of the heart arteries without an acute clot or heart attack.

A very important finding in this study was that nearly two-thirds of those people who arrested during athletic activities had symptoms one week before the event.

The most common symptoms were:

left-side chest pain
shortness of breath
flu-like symptoms

This is similar to what happened to Hughes, who had developed transient chest pain that preceded and warned of the fatal arrest event.

Although women were less likely to have an arrest during athletics than men, the same findings remained important. They often had risk factors of heart disease and symptoms within one week of their arrest.

What This Study Tells Us About Preventing Cardiac Arrest

1. Athletes still need to check for heart disease risks. Athletes are often deemed more fit or healthy, but this does not mean they don’t need an annual doctor’s visit and a thorough assessment of heart disease risk factors such as high blood pressure, diabetes, and high cholesterol. These diseases can occur in the most fit people, too. Managing these conditions can lower heart disease risk. Many of my athlete patients are very surprised to learn they have diseases such as high blood pressure, so it is essential for me, as their physician, to identify it and treat it.

2. We often think athletic-related heart arrests are unexpected; they aren’t. This trial argues that they might be expected when there is a history of heart problems. Most of the arrest victims had risk factors for heart disease, and symptoms that developed before the arrest suggested the possibility of advanced disease. Similarly, Hughes had a significant family history of heart disease, and despite being very athletic and thin, he had exercise-related chest pain prior to his arrest.

Follow your body. If you develop symptoms as described in this column, see your doctor before returning to the athletic arena.

3. Activity and athletics are very good for your body. People who exercise are many times less likely to develop heart disease or experience cardiac arrest. Even in this study, people participating in athletics were less likely to suffer from cardiac arrest than those middle-aged people who were not participating. Even in the setting of heart disease, carefully monitored and prescribed exercise significantly reduces risk of death and positively affects heart disease progression. In a prior column, I address this very issue of exercise for those with heart disease.

4. Finally, athletes may be the last to realize they have heart disease or recognize their symptoms. Encourage those you know to get help if they have heart disease risk factors, to stay compliant with physician-directed treatments, and to take a break from exercise if new heart symptoms develop.

T. Jared Bunch, MD, is a native of Logan, Utah, and directs heart rhythm research at the Intermountain Medical Center Heart Institute. You can follow @TJaredBunch on Twitter.

Photo: iStock.com

Don’t worry about sudden cardiac arrest during exercise

Getting regular exercise is the best way to prevent most types of heart disease—including sudden cardiac arrest.

Images: Thinkstock

Updated: July 17, 2015

Published: July, 2015

New findings may help allay fears about sports-related heart death.

You’ve probably heard at least one account of a middle-aged man who suddenly collapsed and died while exercising. One famous example is James F. Fixx, author of The Complete Book of Running, who in 1984 died of a heart attack at age 52 while jogging.

These anecdotes might give you pause as you lace up your workout shoes. But a new study offers reassurance that exercise-related heart deaths are quite rare, accounting for just 5% of sudden cardiac arrest cases.

“These deaths grab our attention because they’re rare and counterintuitive. But there’s absolutely no question that regular, moderate-intensity exercise is the best way to prevent sudden cardiac arrest,” says Dr. Aaron L. Baggish, associate director of the Cardiovascular Performance Program at Harvard-affiliated Massachusetts General Hospital. The paradox is that if you are going to have a heart-related event, it’s more likely to occur when you’re exercising than when you’re not, he explains.

What can cause sudden cardiac arrest?

Sudden cardiac arrest means the heart abruptly and unexpectedly stops working. It can occur in a person with or without known heart disease. Possible causes include a structural or electrical problem with the heart; dehydration; a serious imbalance of potassium, magnesium, or other minerals in the blood; an inherited condition; or a blow to the chest.

Cardiac arrest is not the same as a heart attack, which is caused by an artery blockage that stops blood flow to the heart. A heart attack can kill part of the heart’s muscle but isn’t necessarily fatal.

However, a heart attack can trigger a malfunction in the heart’s electrical system, which can lead to sudden cardiac arrest. In most of these cases, the heart’s lower chambers beat fast and chaotically, a condition known as ventricular fibrillation. Circulation stops, and death occurs in minutes.

For the study published in the April 21, 2015, issue of Circulation, researchers reviewed 1,247 cases of sudden cardiac arrest in middle-aged men and women over an 11-year period. Of the 63 cases of cardiac arrest that occurred during exercise, most occurred in men, most of whom were jogging, playing basketball, or cycling.

Watch for early warning signs

Two-thirds of these people had known heart disease. In fact, nearly one-third of them had experienced typical cardiovascular symptoms such as chest pain and breathlessness during the week before the sudden cardiac arrest. But the exercisers were twice as likely to survive than people with cardiac arrest from all other causes, probably because they were in public places and more likely to receive quick treatment from a bystander.

In addition to the reassurance that exercise-related cardiac arrest is rare, the study’s other important message is that heart disease often gives warning signs, says Dr. Baggish. If you feel any chest pain during exercise, have difficulty breathing, or even feel more drained than usual, stop and call a doctor for advice.

Recognizing and reacting to cardiac arrest

Someone having a cardiac arrest

suddenly faints or collapses
stops breathing
has no pulse
may have twitching muscles.

If you witness someone collapse from what appears to be cardiac arrest:

Call 911 right away. The sooner professional help arrives,
the better.
Start “hands only” CPR. Push hard and fast (about 100 times a minute if you can) on the middle of the person’s chest. This keeps blood flowing to the brain and the rest of the body. If you aren’t in a public place with a defibrillator handy, keep doing CPR until emergency help arrives. Swap off with a partner if needed.
Use a defibrillator. If you are in a public place such as a fitness center or airport, ask a bystander to find the nearest automated external defibrillator (AED). These user-friendly devices have step-by-step visual and voice prompts that tell you how to use them correctly. An AED shocks the heart out of its deadly rhythm and back to normal.

. Author manuscript; available in PMC 2009 Aug 12.

Published in final edited form as:

Int J Cardiol. 2009 Jan 24; 131(3): 345–349.

Published online 2008 Feb 21. doi: 10.1016/j.ijcard.2007.10.024

PMCID: PMC2725925

NIHMSID: NIHMS101262

PMID: 18206253

Physical activity as a trigger of sudden cardiac arrest: The Oregon Sudden Unexpected Death Study^⋆

Pulla R. Reddy, Kyndaron Reinier, Tejwant Singh, Ronald Mariani, Karen Gunson, Jonathan Jui, and Sumeet S. Chugh^*

Author information Copyright and License information Disclaimer

The publisher’s final edited version of this article is available at Int J Cardiol

See other articles in PMC that cite the published article.

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1. Introduction

Sudden cardiac arrest is a significant public health problem at the global level with at least 200,000 events per year in the US. In spite of advancements in methods of resuscitation, the rate of survival following SCA continues to remain low [1,2]. In large part, the lack of advancement in prevention of SCA is due to a poor understanding of causative mechanisms. There are associations with multiple conditions such as coronary artery disease (CAD), but methods for identification of the high risk patient remain quite inadequate.

Since the majority of sudden cardiac arrests occur due to onset of a fatal ventricular arrhythmia, the substrate–trigger hypothesis is often evoked. This is a traditional concept for genesis of arrhythmia that requires the existence of both a substrate (e.g. coronary artery disease) and a trigger (an external physical or emotional factor believed to incite acute cardiovascular instability in a subject), thereby resulting in SCA. Many have postulated that physical activity and emotional stress are triggers of SCA [3–7]. However, these have not been evaluated in a community-based setting. A better understanding of potential triggers of SCA, particularly among those that suffer SCA in the general population would assist in developing measures to treat and prevent SCA. In this ongoing community-wide Oregon Sudden Unexpected Death Study, we evaluated the role of physical activity as a potential trigger of SCA.

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2. Methods

2.1. Study population

The Study population consisted of all residents of Multnomah County, Oregon, who sustained SCA, from February 1, 2002 to January 31, 2005. Multnomah County, located in northwestern Oregon, covers an area of 435 square miles with an estimated population of 677,813 [8]. All cases of presumed sudden cardiac arrest in Multnomah County were reported to researchers conducting the Sudden Unexpected Death Study (SUDS) at Oregon Health & Science University, Portland, Oregon, by one of three sources: First Responders (Emergency Medical Services, EMS), Medical Examiner (ME) and the 16 hospitals in Multnomah County.

Each of these cases was then independently evaluated by a team of three cardiologists. This process of evaluation used the World Health Organization (WHO) definition for SCA and pre-determined inclusion and exclusion criteria described later in this section. In the event of a conflict of opinion, the majority opinion was considered.

2.2. Inclusion and exclusion criteria

Subjects of all ages and both genders who experienced SCA were included. SCA secondary to trauma, hemorrhage, drug overdose, suicide, pulmonary embolism and malignancy were excluded. Sudden cardiac arrests in terminally ill patients with non-cardiac disease were excluded.

2.3. Data collection

First responder and hospital records of all study subjects were reviewed for demographics and subjects’ activities prior to sustaining SCA. Hospital records, autopsy and medical examiner reports were used for information relating to CAD status.

2.4. Definitions

Witnessed SCA [1]: Sudden unexpected death that occurred within an hour of developing symptoms.

Un-witnessed SCA [1]: Sudden unexpected death in a subject within 24 h of being seen alive and symptom free.

Physical activity was defined as any form of physical activity that a subject was performing immediately prior to sustaining SCA. An estimated metabolic equivalent (MET) score was assigned to each type of physical activity based on the criteria described by Ainsworth et al. [9] and the criteria used by MIOS [10]. One MET [9,10] is the amount of energy spent by a person sitting quietly. Physical activity was classified into five groups: Sleep, Light activity, Moderate activity, Heavy activity and Sexual activity.

Sleep (MET 0.9): subjects who were sleeping when they sustained SCA.

Light activity (MET 1.0–3.4): included bathing, dressing, cooking, cleaning, feeding, household walking and driving.

Moderate activity (MET 3.5–5.9): included walking for exercise, mowing lawn, gardening, working in the yard, dancing.

Heavy activity (MET score ≥6): included sports such as tennis, running, jogging, treadmill, skiing, biking.

Sexual activity (MET score 1.3): included acts of sexual intercourse. We chose to keep sexual activity as a separate category as this activity involves both physical and emotional components.

Coronary artery disease (CAD) [1]: coronary artery obstruction of >50% diagnosed on angiogram or at autopsy or documentation of myocardial infarction, coronary artery bypass graft, or coronary angioplasty in subjects’ medical records.

2.5. Statistical analysis

SPSS 15.0 for Windows (SPSS Inc., Chicago, Illinois) was used for data analysis. Means with standard deviations were used to represent continuous variables. Proportions were used for categorical variables. Oneway ANOVA and Pearson Chi-Square tests were used to detect differences among activity groups for continuous and categorical variables, respectively. Where required, Bonferroni tests were used for post-hoc analysis. P-values <0.05 were considered statistically significant.

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3. Results

The study sample consisted of 1180 subjects, of whom 516 (44%) suffered witnessed SCA and 664 (56%) sustained un-witnessed SCA. Of the 516 subjects, 512 (99%) were adults and 4 (1%) were children.

In adults with witnessed SCA, physical activity information immediately prior to arrest was available in 304 (59%) subjects and analysis was limited to this group of subjects. Of these, 51 (17%) subjects were sleeping, 193 (63%) were performing light activities, 39 (13%) were performing moderate activities, 14 (5%) were performing heavy activities, and 7 (2%) were engaged in sexual activity prior to sustaining sudden cardiac arrest (Fig. 1).

3.1. Age

The mean age of the 304 adult subjects was 69 years. Overall, men with a mean age of 67 years were younger compared to women whose mean age was 71 years ( p-value 0.037). The mean ages of the subjects in the five physical activity groups were: 65 years in those who were sleeping, 72 in the light activity group, 67 in the moderate activity group, 51 in the heavy activity group, and 65 in the sexual activity group. There was a statistically significant difference in the mean ages across these groups (Oneway Anova p-value < 0.001) Table 1. Further analysis using Bonferroni post-hoc tests revealed a statistically significant difference in the mean ages of the subjects engaged in heavy physical activities compared to those who were sleeping and those who were performing light and moderate physical activities ( p 0.02, <0.001 and 0.006, respectively) (Fig. 2).

Table 1

Distribution of mean age, gender and CAD in 304 adults with witnessed sudden cardiac arrest

Sources for p-value:

^*Oneway Anova,

^**Pearson Chi-Square Test.

CAD = Coronary Artery Disease; N = number of study subjects; SD = Standard Deviation.

3.2. Gender

204 (67%) were men and 100 (33%) were women. There was a statistically significant difference in the distribution of men and women across the five physical activity groups (p=0.04) (Table 1 and Fig. 3).

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3.3. CAD

113 (37%) had known CAD. There was no statistically significant difference in the distribution of known CAD across the five physical activity groups (p=0.18), though the individuals in the moderate and heavy activity groups (who were younger) tended to have a lower proportion of known CAD (Table 1).

3.4. Children

Among the four children who sustained witnessed SCA, three were boys aged 1, 11 and 12 years and one was a female infant. The 11 year old boy was running laps at a gym, while the 12 year old boy was learning to ski when he sustained a sudden cardiac arrest.

In the remaining 208 adults who sustained witnessed SCA, physical activity information was not available in their medical records. Nine of these 208 subjects were exposed to a wide range of emotional and behavioral stressors prior to the onset of sudden cardiac arrest. These included: argument; verbal dispute; loss of spouse, child or family member; social isolation secondary to depression; depression secondary to loss of spouse; frequent crying spells; and anxiety attacks. Exposure to emotional and behavioral stressors occurred either immediately prior to the occurrence of SCA or, in some cases, for a prolonged period of time prior to sustaining SCA. Their mean age was 57 years. Of the 9 subjects, 4 were men and 5 were women. Three subjects had known CAD.

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4. Discussion

Our community-wide prospective study described the prevalence of different types of physical activity in adults who sustained witnessed sudden cardiac arrest over a 3 year period. Light physical activity (63%) was the most prevalent, followed by sleep (17%), moderate physical activity (13%), heavy physical activity (5%) and sexual activity (2%).

Previous studies [4–6] have examined the relationship of physical activity and sudden cardiac arrest. Thompson et al. [4] reported that Rhode Island men aged 30 to 64 years engaged in jogging had 7 times the risk of having sudden cardiac death relative to those performing non-vigorous activities (95% CI, 4 to 26). Albert et al. [5] found that the male physicians engaged in vigorous physical activity had 16.9 times the risk of having sudden cardiac death, during or up to 30 min following vigorous activity, relative to periods following lighter activity or no activity (95% CI, 10.5 to 27.0; p-value<0.001). Siscovick et al. [6] observed that in men with low levels of habitual activity, the risk of sustaining cardiac arrest during high intensity activity was 56 times the risk of sustaining cardiac arrest at other times (95% CI 23 to 131). This relative risk dropped to 5, among men with the highest levels of habitual activity (95% CI 2 to 14).

However, there has been a lack of community-based analyses regarding physical activity during sudden cardiac arrest. The results of our study are not directly comparable to the findings of Thompson et al. [4], Albert et al. [5] and Siscovick et al. [6] for several reasons. Firstly, ours was a community-based study, which included adult men and women of all ages, whereas Thompson et al., Albert et al. and Siscovick et al. were limited to men of specific age groups (30–64 years, 40–84 years, 25–75 years) only. Secondly, these three studies [4–6] examined the relationship of one particular type of heavy physical activity to sudden cardiac death, whereas our study examined the relationship of a range of physical activities (sleep; light, moderate and heavy activities and sexual activity) to the occurrence of sudden cardiac arrest. Thirdly, the study designs were different. Thompson et al. was a longitudinal study, while Albert et al. was a case-crossover study nested within a large prospective study, and Siscovick et al. was a case-control study. Ours on the other hand was a prospective study which used a cross-sectional analysis.

Other studies [10–14] have also evaluated the relationship of physical activities and acute myocardial infarction. In the MILIS Study [11], about 23% of the study subjects were performing moderate or heavy physical activities prior to experiencing acute myocardial infarction. In the TIMI II Study [14] 19% of the subjects were engaged in moderate or heavy physical activities, while 81% of the subjects were either asleep, resting or were engaged in mild physical activities prior to the occurrence of acute myocardial infarction. The MIOS [10] reported an increased risk for myocardial infarction in the hour following physical activity. This was 5.9 times higher when subjects were engaged in heavy physical activities relative to less vigorous physical activities or no activity (95% CI 4.6–7.7).

Of all the myocardial infarction studies, our results were most consistent with those of TIMI II. Like in the TIMI II Study [14], about 20% of our subjects were engaged in moderate to heavy activities, while 80% were either asleep or were performing light activities at the time of the event. The prevalence of moderate to heavy physical activity in our study (18%) was slightly lower compared to that in the MILIS (23%) [12] study. The proportion of subjects engaged in heavy physical activity prior to sustaining SCA in our study (5%) was similar to the proportion of subjects engaged in heavy activity prior to sustaining acute myocardial infarction in MIOS (4.4%) [10].

Our study has several strengths. To our knowledge this is the first population based community study that analyzed the prevalence of different types of physical activity in subjects who sustained SCA, using a cross-sectional analysis. SCA cases were identified from a large source population of Multnomah County (677,813) that accounts for about one fifth [8] of the population of the state of Oregon, USA.

Also, methods of case ascertainment used an extensive network of available resources in Multnomah County and this minimized the likelihood of otherwise unidentified cases of SCA. The data collection process involved a comprehensive review of subjects’ medical records, autopsy and medical examiner records. This helped reduce misclassification of cases. Having clear definitions for SCA, well defined eligibility criteria and a team of three cardiologists to screen cases also helped reduce misclassification. Lastly, our analysis was appropriately limited to subjects with witnessed SCA and known physical activity information. This enabled us to perform a more scientific evaluation of the physical activities prior to the occurrence of SCA.

Potential limitations of this study include a lack of adequate description of physical activities immediately prior to the event in 41% of adults who experienced witnessed SCA. However, this is consistent with the dynamic and catastrophic nature of the event. As a result, obtaining precise physical activity information prior to SCA is a challenge. There were no statistically significant differences in the distribution of mean age and CAD in adult subjects with and without physical activity information as shown in Table 2, but gender proportions were different. We believe that information may have been missing at random and therefore, is unlikely to have resulted in a significant bias.

Table 2

Distribution of mean age, gender and CAD in 512 adults with witnessed sudden cardiac arrest

Sources for p-value:

^*t-test,

^**Pearson Chi-Square Test.

CAD = Coronary Artery Disease; N = number of study subjects; SD = Standard Deviation.

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5. Conclusions

In this community-based study, only 5% of SCA victims were performing vigorous physical activity immediately prior to the fatal event. The vast majority (80%) of the adult subjects that suffered sudden cardiac arrest were performing light physical activity or was asleep at the time of the event. The potential role of emotional or behavioral stressors as well as sleep-related disorders, which this study was not designed to evaluate, warrants further assessment.

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Acknowledgments

The authors are grateful to the first responders (American Medical Response, Portland and Gresham fire departments) and health care providers of the Portland, Oregon metropolitan area, without whom this study would not have been possible.

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Footnotes

^⋆Funded, in part, by R01HL088416 (SSC) and The Donald W. Reynolds Clinical Cardiovascular Research Center Grant to Johns Hopkins University (SSC).

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References

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Population	Incidence of SCA
General Population Overall incidence of SCA
Chugh S et al¹ Vaillancourt C et al² Byrne R et al³	530 per million per year 530 to 590 per million per year 512 per million per year
General Population Sport related SCA incidence
Berdowski J et al⁴ Marijon E et al⁶ Marijon E et al⁷	21 per million per year 22 per million per year 4.6 per million per year
Athlete Sport related SCA incidence
Kim J et al⁹ Harmon K et al¹⁰	5.4 per million marathon participants 18.6 per million per athlete year

Sudden Cardiac Arrest and Extreme Exercises

Extreme athletes share determination, maybe risk

Results of review

What is behind the heart risks

What this means for you

Exercise guidelines

Warning Signs

By Dr T. Jared Bunch, MD

Cardiac Arrest Is More Common as Athletes Age

Risk of Sudden Cardiac Death Between Ages 35 and 65

Warning Signs a Week Before Cardiac Arrest During Sports

What This Study Tells Us About Preventing Cardiac Arrest

Gyms (and How to Prevent It From Happening to You)

Why AEDs are so important in gyms

How to operate an AED

How else can gym-goers protect themselves?

Don’t worry about sudden cardiac arrest during exercise

What can cause sudden cardiac arrest?

Watch for early warning signs

Recognizing and reacting to cardiac arrest

Physical activity as a trigger of sudden cardiac arrest: The Oregon Sudden Unexpected Death Study⋆

1. Introduction

2. Methods

2.1. Study population

2.2. Inclusion and exclusion criteria

2.3. Data collection

2.4. Definitions

2.5. Statistical analysis

3. Results

3.1. Age

Table 1

3.2. Gender

3.3. CAD

3.4. Children

4. Discussion

Table 2

5. Conclusions

Acknowledgments

Footnotes

References

Physical activity as a trigger of sudden cardiac arrest: The Oregon Sudden Unexpected Death Study^⋆