Back in 1999, UCSF researchers strapped some high tech motion detectors onto about 30 patients on dialysis and compared one week’s worth of activity to that of matched controls. Mind you, these control patients were selected to be sedentary—i.e., they told the researchers that they exercised less than once a week on average.
The patients on dialysis were 35% less active than even these sedentary controls. Similarly low levels of physical activity have been confirmed again recently; nearly 95% of patients on dialysis in this study met criteria for “low fitness.”
Okay so what? We all know that our patients tend to be over 60 years of age, and some have peripheral vascular disease or other comorbidities that limit their mobility. We already talk to them about taking their phos binders and eating less salt, do they really need advice about how much they should move about?
Here are some arguments that suggest this this just might help:
• We know that patients on dialysis tend to have a higher burden of cardiovascular disease and diabetes, compared to the general population. And exercise not only prevents a heart attack in an other wise healthy individuals, it also prevents secondary events in individuals who already have some of the comorbidities. For example patients with diabetes who walk two hours per week can drop their all cause cardiovascular mortality to one-third of that seen in sedentary diabetics.
• Just like in the diabetics, being sedentary increases the risk of mortality in our patients as well. In one of the largest observational studies to date, patients who never exercised had a 60% higher chance of dying during their first year of dialysis compared to others who reported that they at least attempted to exercise. This increase in mortality risk is the same as if the patient had an albumin of 2.5 mg/dL compared to 3.5 mg/dL for example.
• Exercise preserves function later in life. Studies have shown a reduction in falls, cognitive impairment and physical function (i.e. ability to complete activities of daily living) in elderly people who exercise.
So both from a longevity and quality of life point of view, our patients would be helped by exercise. There is a lot of back-and-forth about why patients on dialysis tendency towards being sedentary—is it the burden of comorbidity, is it a uremic toxin that saps their muscle strength, or is the procedure itself (when we talk about hemodialysis in particular)? We don’t know yet.
Other people are looking into whether to push aerobic or resistance exercise. But very few studies have tried innovative ways of incorporating exercise into the dialysis session. And in this world of expensive treatments, converting a few dialysis chairs into stationary bikes in the dialysis center may be our most cost effective intervention! Failing that, we should at least mention the bike during our rounds.
Suchi Anand, MD