Ask the Doctors May 2019 Issue

Ask The Doctors: May 2019

Q: For years I have heard that exercise helps prevent heart attack, but can it help me live longer? Are there limits to how much exercise I should do?


Michael Rocco, MD, medical director of Cardiac Rehabilitation and Stress Testing at Cleveland Clinic

A: A positive relationship between fitness levels and cardiovascular disease, hypertension, stroke and cancer has been reported for years. Studies have consistently shown that mortality decreases as fitness levels increase. Yet some studies have suggested that at very high levels of regular exercise the benefits plateau, and there may even be detrimental effects.

Is too much or too intense exercise bad? A recent Cleveland Clinic study analyzed the death rate of more than 122,000 patients who had undergone stress testing and were followed for an average of 8.4 years. Cardiorespiratory fitness (CRF) levels measured the regularity and intensity of exercise.

The patients were divided into five groups based on level of fitness. The highest fitness category (comparable to endurance athletes) had the lowest mortality rate (80 percent lower than the least-fit group) even when the analysis controlled for age, gender and heart risk factors. Mortality dropped with each progressive level of CRF, with no upper limit at which the benefits declined or flattened. The benefit of high performance was seen in both genders and in subgroups older than70.

Of note, the mortality risk from poor exercise performance was comparable to that of cardiac risk factors such as diabetes or smoking. This supports the concept of low activity as an important and treatable risk factor. This is not to say that extreme levels of exercise are appropriate or even safe for all people. However, since fitness level is a modifiable indicator of long-term mortality, maintaining the highest level of regular activity shown to be safe for you is reasonable. Talk to your physician or consider obtaining exercise guidelines from stress testing in the context of a cardiac rehab program to help determine the best exercise level for you.

Q: I have atrial fibrillation (AF) and am being treated with anti-arrhythmic medications and blood thinners. I still experience AF sometimes, mostly at night. Should I be worried?

A: Recurrences of AF are not uncommon, nor are nighttime events. When the heart rate drops during sleep, electrical activity from areas other than the heart's normal pacemaker can trigger AF. Factors associated with AF include advancing age, coronary and structural heart disease, lung disease, high blood pressure, thyroid disease, diabetes and inflammation of the heart's lining. Obstructive sleep apnea (OSA), a disorder that disrupts breathing during sleep, is often an unrecognized trigger forAF.

If your episodes occur primarily at night, it's very possible that you have OSA and may not be aware of it. Clues include snoring, interruptions in breathing during sleep and daytime fatigue.

Several studies have demonstrated a strong relationship between AF and OSA. Forty to 50 percent of patients with AF have OSA, and individuals with OSA have a four-fold increased risk of developing AF. Furthermore, studies have shown that untreated OSA can make AF treatment with medications or ablation less effective. In addition to the heightened AF risk, OSA is associated with increased risk of high blood pressure, heart failure and sudden death.

With your nocturnal AF history, particularly if you experience snoring or daytime fatigue, it is reasonable to have a sleep study. Treating OSA and managing other AF triggers may reduce the likelihood of recurrent AF episodes.

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