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Physical Activity Levels and Atrial Fibrillation

May 23, 2014 By Larry Creswell, MD 1 Comment

In the medical news last week came another interesting report on the relationship between physical activity and atrial fibrillation (AF). Reported in the medical journal, Heart, a team of investigators led by Nikola Drca from the Karolinska Institute in Stockholm gave us a study entitled “Atrial fibrillation is associated with different levels of physical activity levels at different ages in men.” This is the largest-ever study of the relationship between physical activity and AF, so the findings and conclusions deserve our attention here in the athlete community.

To set the stage for our discussion, recall that AF is a fairly common arrhythmia that is generated in the upper chambers of the heart–the left and right atrium. I’e written about AF here at the blog previously, in general terms for athletes. We’ve known for a long time that AF is associated with some other types of heart disease, particularly heart valve disease, and increases in prevalence as we age. The problem of AF is not benign. For athletes, the arrhythmia disrupts training or competition, but over the long term there is a small but real risk of stroke and also the chance of harm to the heart itself. Moreover, the available treatments–medications or ablation procedures–carry risk as well.

We also know that AF is associated with exercise. We know from prospective, longitudinal population studies that long-time, regular exercisers are more likely to develop AF over the years. And we know from targeted studies that athletes in the endurance sports are particularly at risk for developing AF.

Healthy endurance athletes should be asking the questions like:

What are my chances of developing AF?
How can I exercise safely and avoid developing AF?

Questions like these motivated the current study. Let’s take a look….

The Study

The purpose of the study was to determine if there was an association between physical activity level and the development of new AF in middle-aged men.

Back in 1997-1998, the investigators contacted all of the men aged 45-70 years who were residing in 2 counties in central Sweden and asked them to participate. About half (48,850 men, or 49%) responded by completing a questionnaire. From these, several thousand were excluded from further study because of: missing data on the questionnaire, death before the study’s follow-up period began, a current diagnosis of AF (1,496 men, or about 3% of the entire group), and the current diagnosis of some forms of cancer. This left 44,410 men to be part of the study. The average age of the participants at the time of enrollment was 60 years.

The questionnaire asked 2 questions about the amount of physical activity that the men engaged in. They were asked to think back and to recall their activity levels at age 15, at age 30, at age 50, and at the current (“baseline”) time. The participants younger than 50 years only answered for age 15 and for age 30 and “baseline.” The questions were:

“How many hours per week do you engage in leisure-time exercise (such as running, soccer, bicycling, swimming, floorball, gymnastics, cross-country skiing, etc.)?”

The respondents had to choose between:

<1 hour
1 hour
2-3 hours
4-5 hours
>5 hours.

“How much time each day do you spend walking or bicycling for everyday transportation purposes?”

The respondents had to choose between:

<20 min per day
20-40 min per day
40-60 min per day
>1 hour per day

In addition to the questions about physical activity, the respondents provided information about their medical history, smoking history, family medical history, medications, alcohol consumption, and level of education.

The respondents were then followed for 12 years to see what happened to them….and, in particular, to see if they developed AF.

The Results

At the end of the 12 years, there was an accumulated experience of 476,112 person-years! And during that time, there were 4,568 new cases of AF. Doing the math, that works out to 9.6 cases of AF per 1,000 person-years. Put another way, of the 44,410 participants, about 10.3% developed AF.

But the goal of the study was to determine if the individuals’ activity level was related to their chance of developing AF.

The primary finding of the study was that the self-reported leisure-time exercise at age 30 was indeed associated with the risk of developing AF. The investigators performed a statistical analysis designed to isolate the effect of the number of hours of exercise per week (and eliminating, as best possible, the effects of other influences on the risk of AF). They showed that the risk of developing AF was 19% greater among the individual who exercised >5 hours per week (at age 30) compared to those who exercised <1 hour per week. Remember that overall, 10.3% developed AF….so in terms of absolute risk difference between the extremes of exercise level reported at age 30, we’re talking about a couple percentage points different in the chances of developing AF. It’s because of such a large number of participants that differences this small can be detected.

Another important finding of the study was that the self-reported leisure-time exercise at baseline (when participants enrolled in the study, at mean age 60 years) was not related to the development of AF. And furthermore, the investigators found no relationship between the amount of self-reported leisure-time exercise at age 15 or at age 50 and the development of AF. The only such relationship was for the activity level at age 30.

The last important finding of the study came from a subgroup analysis. The participants who were at greatest risk of developing AF were those who reported >5 hours per week of leisure-time exercise at age 30….and <1 hour per week of leisure-time exercise at the time of enrollment in the study. These individuals were 49% more likely to develop AF during the 12-year follow-up period than individuals who exercised <1 hour per week at both age 30 and at the time of enrollment in the study.

There was no relationship between the amount of walking/cycling for transportation purposes at any age and the development of AF.

The Take-home Messages

The current study adds to our knowledge about exercise and AF. I hope that more studies are to come.
The relationship between exercise and AF is not completely understood and, indeed, the relationship may not be straightforward. Studies like this one ask participants to recall and note their activity levels at just a few moments during their lifetime. That can be hard to do, memory being what it is. Undoubtedly, the risk for developing AF must be related to some sort of dose of exercise over time. In retrospect, that’s hard to quantify. People exercise more some years than others. Some start exercising and some stop. They start and stop different types of exercise. I’ll bet that the intensity is important, too, yet how do we quantify this (in some straightforward way) so that analyses can be performed?
Previous studies, both in large longitudinal cohorts as well smaller invetigations of particular endurance athletes, have shown an increased risk of AF over the long term among individuals who exercised a lot. This phenomenon has been shown best for individuals in young to middle age, and for men more so than women. This relationship has been shown in enough different populations that we should accept it as fact. The current study points out that the increased relative risk compared to non-exercisers may reflect a rather modest increase in absolute risk. But that’s at odds with previous studies that have shown as much as a several-fold increased risk for AF among heavy exercisers. But whatever the magnitude, that risk must be considered together with the other, well-established benefits of exercise over the long term when athletes are making decisions about their activity level. Don’t forget that exercisers live longer. That’s an important endpoint to keep in mind.
The current study is curious in at least one respect. At first glance, it seems a bit odd that a relationship between exercise and development of AF could only be established for the amount of exercise reported at age 30…..and not at age 15, 50, or at the time of enrollment. Why is that? Could it be possible that we should exercise freely, with no worry about AF, while we’re young….and then again when we’re old? Maybe the 30-year-olds exercise with greater intensity. Maybe they accumulate more hours of exercise over more years. Maybe they engage in different forms of exercise that carry more risk. Perhaps “>5 hours” for the 30-year-olds was actually much more than 5 hours. The current study doesn’t provide answers. This needs to get sorted out with future studies. We need to better define the safe dose of exercise with respect to AF.
Finally, why is exercise associated with AF? In truth, we don’t know in any detail. It seems that it must have something to do with the structure of the atrium that changes over years’ time with exercise. The investigators note several of the potential reasons: enlargement of the atrium, inflammatory changes in the atrium, and overdevelopment of the parasympathetic portion of the autonomic nervous system. Perhaps all of these play a role. I like Dr. John Mandrola’s blog post this week about this issue. I like his take.

2. In the News: Atrial Fibrillation in Cross Country Skiers

3. Atrial Fibrillation in Athletes (In a Nutshell)

Adderall, Athletes, and the Heart

November 2, 2013 By Larry Creswell, MD 2 Comments

Last week I got an inquiry from a reader about the prescription drug Adderall, asking in particular about the heart risks for athletes who might be taking the drug.

Although we’ll be talking about Adderall in particular, much of the information here will apply to other stimulants as well.

My quick take….

Like any drug, there’s both good and bad with Adderall. For athletes who legitimately need the drug, though, the heart risks appear to be small provided that the athlete doesn’t have any serious underlying heart problems. The drug can probably be used safely if both athlete and physician are aware of the potential risks.

What is Adderall?

Adderall is the brand name for a central nervous system stimulant composed of a 3:1 mixture of the salts of d-amphetamine and l-amphetamine. The U.S. Food and Drug Administration (FDA) has approved its use for the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy.

The drug is available in immediate release and extended release forms (Adderall XR) in dosages of 5-30 mg. Generic formulations are also available.

The U.S. Drug Enforcement Agency (DEA) has placed Adderall on its Schedule 2 list of drugs–those with a high potential for abuse, with the potential for leading to severe psychological or physical dependence. There are both federal and state regulations that apply to prescriptions for Schedule 2 drugs. In my home state of Mississippi, a handwritten prescription is required, refills are not permitted, and the prescription must be filled by a pharmacy within 90 days. There are stiff penalties for trafficking in Schedule 2 drugs.

In the United States, the prevalence of ADHD in children age 4-17 is nearly 10% and the prevalence in adults is nearly 5%. About two thirds of affected children are treated with prescription drugs.

Adderall and the Athlete

For athletes, there seem to be 3 relevant questions:

What are the rules governing the use of Adderall by athletes?
Does Adderall provide a competitive advantage?
What are the risks?

The Rules

For NCAA athletes, all stimulants are banned. There is a policy which allows for medical exceptions for banned substances that are used for legitimate medical purposes. In the case of Adderall, pre-approval from the NCAA is not needed for use, but the athlete must maintain documentation from his/her physician in the on-campus medical record that includes the diagnosis, course of treatment, and current prescription. If such an athlete is tested positive for the stimulant, the documentation is then used, after the fact, to obtain an exception from penalty.

All stimulants are included in the World Anti-Doping Agency’s list of substances that are banned in-competition. The WADA banned substance list has been adopted by all sports federations of the Olympic movement and many others as well. A complete list of signatories can be found at the WADA website. Athletes with a legitimate medical need for a banned substance can apply for a therapeutic use exemption (TUE). Information about the process for obtaining a TUE is posted at the WADA website. WADA recommends reassessment for the need for continued treatment every 3-4 months.

Adderall and other stimulants are banned by the National Football League (NFL), Major League Baseball, National Basketball Association (NBA), Major League Soccer, but athletes can obtain a therapeutic use exemption. Interestingly, nearly 10% of Major League Baseball players have obtained such an exemption. The drug is banned completely in the National Hockey League (NHL).

Competitive Advantage?

When used to treat ADHD, particularly as part of an comprehensive treatment plan that includes psychological, educational, and social measures, Adderall can be effective in reducing the inattentive or hyperactive-impulsive symptoms that are characteristic of the disorder.

In individuals without ADHD, the effects of Adderall are not characterized as completely. Nonetheless, there is reportedly increasing use of Adderall in this situation, particularly among college students and various athlete groups. In the college setting, students take stimulants like Adderall to increase their attentiveness and reduce their fatigue, especially in situations such as studying for exams or completing end-of-term projects.

There is also ample reason to believe that stimulants such as Adderall might provide a competitive advantage for athletes. From my vantage point, this issue doesn’t seem to be very well studied (in large part because of the bans), but there is at least some evidence to show that these drugs can produce increases in both strength and endurance, better concentration, and improve reaction time, especially when fatigued.

The Risks

For Adderall, like any prescription drug, information about the known risks can be found in the drug’s package insert.

Let me quote the entire black box warning:

Amphetamines have a high potential for abuse. Administration of amphetamines for prolonged periods of time may lead to drug dependence and must be avoided. Particular attention should be paid to the possibility of subjects obtaining amphetamines for non-therapeutic use or distribution to others, and the drugs should be prescribed or dispensed sparingly. Misuse of amphetamine may cause sudden death and serious cardiovascular adverse events.

A variety of side effects are mentioned in the package insert, including emergence of new psychotic or manic symptoms, aggression, long-term suppression of growth, seizures, and visual disturbances. Mention is also made that the effects of long-term usage are not well studied and that the usefulness of the drug for any particular patient should be carefully assessed periodically.

The package insert goes on to discuss cardiovascular warnings.

In children and adolescents, sudden death has been reported in patients treated with Adderall who also have heart problems like structural heart abnormalities, cardiomyopathy, or heart rhythm abnormalities. Patients with any of these heart problems are advised NOT to take Adderall.

In adults, sudden death, stroke, and heart attack have all been reported in patients taking Adderall at typical prescription dosages. It is recommended that patients with structural heart abnormalities, cardiomyopathy, serious heart rhythm abnormalities, or coronary artery disease should NOT take Adderall.

For any patient with high blood pressure, special precaution is advised when prescribing Adderall. Because Adderall is known to increase both the heart rate and blood pressure, special caution and careful follow-up is recommended.

Recommendations are offered for the cardiac evaluation of patients who are being considered for treatment with Adderall. Attention should be devoted to a careful medical history, family history (with particular attention to sudden death, ventricular arrhythmias), and physical exam that focuses on heart and vascular health. Additional investigation with EKG and echocardiogram may be indicated depending on the findings. Finally, patients treated with Adderall who develop any serious warning signs of heart disease (eg, exertional chest pain/discomfort, syncope or blacking out) should be re-evaluated.

Summary

In summary, Adderall is a stimulant that is effective for the treatment of patients with ADHD. Although prescription use of the drug is tightly controlled, there is ample prescription mis-use of the drug among individuals without ADHD or other medical reason for its use. For athletes, the drug is performance-enhancing and is banned by many sports organizations. Whatever its use, Adderall carries a small but real risk of serious cardiovascular side effects, especially among users with underlying heart conditions, whether known or unknown. Athletes and their doctors should be aware of these risks and consider cardiovascular screening and careful cardiovascular follow-up when this drug is used.

Related Posts:
1. Heart Medications, WADA, and the Athlete

Anabolic Steroids and the Heart

June 12, 2013 By Larry Creswell, MD 8 Comments

I had a chance earlier today to visit with the production crew from Mississippi Public Broadcasting. They’re working on an upcoming television program on body building and were looking for information about the cardiovascular effects of anabolic steroids.

Also today, I came across a new study published this week (online, ahead of print) in the medical journal, JAMA Internal Medicine, that reported on a 40% increase in testosterone replacement therapy in middle-aged men during the time period from 2001-2011. The authors noted that testosterone replacement therapy was often prescribed without an established diagnosis of low testosterone levels (hypogonadism).

So….with steroids on my mind, I thought I’d share some information about these drugs, particularly as they relate to athletes.

What are Anabolic Steroids?

The history of anabolic steroids dates to the mid-1930s when the chemical structure of the male sex hormone testosterone was elucidated. Soon afterward, chemical synthesis of testosterone was possible in the laboratory.

The group of medications that we call anabolic steroids are synthetic derivatives of testosterone. These medications have a variety of arcane names including: nandrolone, methandienone, stanozolol, androsterone, and androstane, among others.

The anabolic steroids have 2 major groups of effects: androgenic effects and anabolic effects. The various available steroids differ from one another in the relative potency of these 2 sets of effects. Each manufacturer’s drug might then be targeted toward a specific use that focuses to a greater extent on one or the other of these sets of effects.

Clinically, the U.S. Food and Drug Administration has approved the use of anabolic steroids for: hypogonadism (eg, low testosterone level); generalized wasting in conditions such as human immunodeficiency virus infection (HIV), acquired immunodeficiency syndrome (AIDS), or cancer; hypoplastic anemias that accompany bone marrow failure or renal failure; growth stimulation in children with growth failure; male contraception; induction of male puberty; and gender identity disorder.

These medications can be delivered orally, intravenously, by intramuscular injection, or by transdermal patch.

The anabolic steroids should not be confused with the corticosteroids that are much more commonly used in clinical practice.

In 1990 the anabolic steroids were added to Schedule 3 of the Controlled Substance Act, making it a federal crime to possess these drugs in the United States without a prescription. For context, other drugs in Schedule 3 include the barbiturates, LSD precursors, ketamine, and some narcotic analgesics. The laws regarding the prescription and possesion of anabolic steroids vary from country to country.

Anabolic Steroids and Sports

The anabolic steroids have been used for decades by athletes of many different sports to gain competitive advantage. Used for this purpose, these drugs are often taken at many times the conventional prescription dosage. At these dosages, the anabolic steroids lead to an increase in muscle mass and likely potentiate the effects of exercise on gaining additional muscle mass and strength.

The first reliable tests for the detection of steroids (or their metabolites) became available in 1974 and anabolic steroids were added to the International Olympic Committee’s (IOC) banned substance list in 1976 and have been on the World Anti-Doping Agency (WADA) banned substance list since its inception in 1999. As such, these drugs are banned by the entire Olympic movement and by all sports organizations that adhere to the WADA code. In addition, these drugs are prohibited by the majority of professional sports organizations in the United States, including the National Football League, National Hockey League, National Basketball Association, and Major League Baseball.

How Many People are Using Anabolic Steroids?

The number of Americans currently using anabolic steroids is unknown, but some estimates have placed that number at more than 3 million. In surveys of steroid usage among body-building or power athletes, rates of up to nearly 70% have been reported, with considerably greater usage among male athletes.

What are the General Side Effects?

Many unwanted side effects have been attributed to anabolic steroids. Some are drug-specific and dose-dependent. The list of adverse effects of anabolic steroids includes: in men, enlargement of the breasts (gynecomastia), suppression of naturally-produced testosterone, decreased sperm production, and testicular atrophy; in women, increases in body hair, decreases in menstrual cycles, and lowering of the voice; development or worsening of acne; and alterations in the mood, with increased aggression. In order to avoid the unwanted side effects of gynecomastia and weight retention, men who use steroids sometimes also take drugs (eg, Arimidex) that limit conversion of the steroids to estrogen.

What are the Adverse Cardiovascular Effects?

Our understanding of the cardiovascular effects of the anabolic steroids comes from a relatively small set of observations made in athletes taking these medications and from a small number of animal studies. Retrospective human studies in this area suffer from important methodologic problems such as: incomplete or inaccurate reporting on drug dosages by athletes; confounding influences of other supplements or medications that athletes may be taking; and the cardiovascular effects of an athlete’s training routine that may mimic some of the effects of steroids.

Some, but certainly not all studies, have shown an increase in blood pressure attributed to anabolic steroids. This issue has been difficult to study in power athletes because of the myriad of factors that influence the blood pressure, including weight-lifting itself. There are certainly anecdotes of finding cases of severe hypertension in athletes who have no other obvious cause than steroids. The amount of blood pressure elevation associated with long-term use of steroids appears to be mild to moderate and the effect may subside if the steroids are stopped.

The majority of studies show that anabolic steroids have an unfavorable effect on the serum lipid profile. These medications can lead to a 20% increase in the unhealthy, “bad” cholesterol (LDL) and also a 20% decrease in the healthy, “good” cholesterol (HDL). The exact mechanism for these changes has not been established. These changes are thought to develop within weeks of starting steroids and can linger for months after these medications are stopped, despite a relatively short pharmacologic half-life measured in days. Some studies have suggested that the oral route of administration may be worse in this regard than the injectable route. These unfavorable changes in the serum lipid profile are noteworthy because there is considerable evidence that high LDL and low HDL levels are associated with increased risk for coronary artery disease, heart attack, and stroke.

Athletes who use anabolic steroids are often found to have thickening of the muscular walls of the left ventricle that we call left ventricular hypertrophy (LVH). The degree of hypertrophy can range from mild to severe. But to date, there has not been a long-term, carefully controlled, prospective study to help sort out the precise effects of steroids. The data regarding which portions of the left ventricle become hypertrophied have been inconsistent, but it appears that the resulting LVH may not be uniform throughout the chamber. It’s important to remember, though, that power exercise alone can produce LVH and that elevated blood pressure alone can produce LVH, and both of these influences will be in play in power athletes.

Sudden cardiac death (SCD) may occur in athletes who are taking anabolic steroids. This appears to be a rare event. In the absence of any other explanation, it might be easy to ascribe such deaths in otherwise healthy athletes to the steroids. But we can only speculate now about the mechanism by which steroid use might predispose the athlete to SCD. Nonetheless, there have certainly been athletes with SCD where autopsy findings have shown severe LVH or cardiac fibrosis (which might predispose to arrhythmias) where no potential cause except the steroids was obvious.

Acute myocardial infarction (MI), or “heart attack” may occur in young athletes who are taking anabolic steroids, often without any prior indication of heart disease. The cause-and-effect relationship between steroids and MI is not completely understood, but we know from animal studies that the steroids may increase platelet aggregation–a step that occurs clinically during sudden blockage of one of the coronary arteries during acute MI. We also know from animal studies that the steroids may increase oxygen demand of the cardiac muscle, potentially leading to a mismatch in blood/oxygen supply and demand during exercise. This may also play a role.

The precise epidemiologic link between steroid use and mortality is yet to be established. Small studies have shown that among users of anabolic steroids, the cause of death, perhaps not surprisingly, is cardiac in up to two thirds. One interesting recent study from Sweden identified users of anabolic steroids by blood tests (toxicology screen) that were administered during evaluations for some other medical problem. The investigators found that, over a several-year period, the mortality rate for users was 2-5 times that for non-users. The study was not controlled, though for many other, potentially important, factors that influence mortality.

Some Thoughts

To reiterate, our current understanding of the adverse cardiovascular effects of anabolic steroids is based on rather limited information gathered from a small number of research studies. The available reports, though, certainly give a glimpse of unwanted cardiovascular effects that may occur, even if the causal mechanisms are not yet understood. Going forward, we are unlikely to have large-scale prospective studies to gather more information and additional retrospective studies are likely to have the methodologic pitfalls I mentioned above. Given our current understanding, athletes who choose to use anabolic steroids should be aware of the possibilities of high blood pressure, unfavorable lipid profile, structural changes in the heart, and even heart attack or SCD.

Athletes and Statin Medications

May 8, 2012 By Larry Creswell, MD 7 Comments

Check out my column this month at Endurance Corner. I talk about the pros and cons of the lipid-lowering agents, the so-called statin medications, particularly for otherwise healthy athletes. There are special considerations for athletes and non-athletes, alike, who might take these medications for primary prevention–preventing the first problem with heart or vascular disease.

Viagra: Does it Improve Athletic Performance?

December 19, 2011 By Larry Creswell, MD 2 Comments

My friend, Scott, used Twitter to ask me about Viagra a couple weeks ago. He was riding on his trainer and saw an advertisement on the TV about Viagra….and he was wondering if it could enhance his athletic performance.

Here’s what I’ve learned….

Introduced in 1998, Viagra is one of the trade names for the compound, sildenafil citrate. Manufactured by Pfizer, this drug is used primarily to treat erectile dysfunction (ED), but it has also found niche uses as well for the treatment of pulmonary arterial hypertension (PAH, high blood pressure in the lungs) and altitude sickness. Viagra is similar in properties to both Cialis (tadalafil) and Levitra (vardenafil).

By inhibiting an enzyme in the penis called cGMP-specific phosphodiesterase type 5, Viagra actgs by increasing bloodflow that produces an erection. We call drugs like Viagra vasodilators because they dilate the blood vessels. It’s taken in a pill form, at a dosage of 25 – 100 mg, and is recommended for use not more than once per day, sometime between 30 minutes to 4 hours prior to sexual intercourse.

But if Viagra can produce greater bloodflow in the penis, could it also produce increased bloodflow elsewhere in the body? And, as a result, might it lead to increased oxygen delivery to the muscles in a way that could enhance athletic performance?

Interestingly, we learned during the Balco investigation that many professional baseball players and other athletes were using Viagra as an on-field performance-enhancing agent. In fact, in 2008 Victor Balco claimed that the use of Viagra was even more common than the use of creatine.

The science about Viagra and athletic performance is actually very sparse.

Interest in this regard was stimulated by a study of 14 mountaineers and trekkers by a group of investigators at the University of Giessen in 2004 [1]. They studied the athletes using a cycling test at near sea level (in Giessen), with a reduced-oxygen environment, and again at Mt. Everest Base Camp (5245 m). They found that Viagra increased the maximum workload in each setting and concluded that “sildenafil is the first drug shown to increase exercise capacity during severe hypoxia both at sea level and at high altitude.”

There’s been just 1 other study in humans to show a direct benefit of Viagra on athletic performance [2]. A group of investigators from Stanford hypothesized that Viagra would improve the cardiac output (CO), arterial oxygen saturation (PaO2), and performance at altitude (relatively low oxygen environment), but would have no effect at sea level (with a normal level of atmospheric oxygen). They studied 10 cyclists with a 10 km time trial (TT) at both sea level and simulated high altitude (3874 m). At sea level, Viagra had no effect on the outcome measures. At altitude, Viagra produced higher CO, higher PaO2, and a 15% improvement in time for the 10 km TT. On review, though, the investigators found that there were actually 2 subgroups: a group of Viagra responders, who improved their TT performance by 39% and a group of non-responders who improved their TT performance by only 1% (which was not statistically significant). The authors concluded that Viagra can greatly improve cardiovascular function and performance in a low-oxygen environment for certain individuals.

But, of course typical athletes don’t compete at altitudes of 2+ miles!

The issue of whether Viagra might affect athletic performance drew the world’s attention heading into the Beijing Olympic games in 2008. In assembling its list of banned substances for 2008, the World Anti-Doping Agency (WADA) wrote:

“As regards sildenafil (Viagra), WADA is aware of studies presented in relation to the potential of sildenafil to restore pulmonary capacities at very high altitudes. WADA is currently funding a number of research projects on the effects of sildenafil at various altitudes. These projects are ongoing.”

Indeed, Viagra has not yet been added to the WADA list of banned substances.

In summary, then, Viagra is useful for the treatment of ED and PAH. Although there is some evidence of performance-enhancing effects on athletic performance (in some individuals) at altitude, there is no evidence that Viagra improves performance in typical athletic activities.

References:

1. Ghofrani HA, Reichenberger F, Kohstall MG, et al. Sildenafil increased exercise capacity during hypoxia at low altitudes and at Mount Everest Base Camp. Ann Int Med 2004; 141:169-177.

2. Hsu A, Bamholt KE, Grundmann NK, et al. Sildenafil improves cardiac output and exercise performance during acute hypoxia, but not normoxia. J Appl Physiol 2006; 100:2031-2034.