By Dr. Geoffrey Modest
A couple of concerns about the exercise prescriptions we give patients: How realistic are they are for the elderly; and when older people cannot do the moderate-to-vigorous activities recommended, is there benefit in less aggressive exercise? A systematic review and meta-analysis was recently done to answer these questions (see doi:10.1136/bjsports-2014-094306).
Details:
- 9 prospective cohort studies were found, with 122,417 participants (73,745 women and 48,672 men, mean age 72.9, average cohort size 13,602, six cohorts were American/2 from Pacific region/1 Asian, follow-up of 9.8 years and with 18,122 deaths (14.8%)
- They defined 4 activity levels, by Metabolic Equivalent of Task, or MET) minutes: inactive, low (1-499 MET-minutes), medium (500-999) and high (>1000)
- Results, with inactive being the reference:
- Low activity had a 22% reduction in mortality [RR 0.78 (0.71-0.87), p<0.0001]
- Moderate activity had a 28% reduction in mortality [RR 0.72 (0.65-0.80), p<0.0001]
- High activity had a 35% reduction in mortality [RR 0.665 (0.61-0.70), p<0.001]
- Most of this association was for a reduction in cardiovascular disease (i.e. 25% reduction in low, 26% medium and 40% high activity), though the reduction in cancer mortality was also significant (ie 11% reduction in low, 16% medium and 31% high activity)
- There was a dose-response curve, with more exercise intensity having more mortality benefit. But, the greatest decrease in mortality was associated with increasing from inactivity to the lowest level, with gradually more benefit as the intensity increases further.
- Women benefited more than men: for those performing low activity exercise — men had 14% mortality reduction vs 32% in women (??do men overestimate their amount of exercise and women underestimate it??)
So, a few points:
- For further clarification of METs and MET-minutes, see http://health.gov/paguidelines/guidelines/appendix1.aspx . As a rough guide: sedentary/resting energy expenditure is 1 MET; moderate activity is 3-5.9 METs, and walking 3 miles per hour is 3.3 METs; high activity is >6.0 METs, and running at 10 minutes/mile is a 10 MET activity.
- Approximately 60% of older people cannot do 150 min of moderate-to-vigorous activity/week
- These 9 studies were observational, though they controlled for many risk factors for mortality, such as smoking, blood pressure, fasting blood sugar, lipids, parental history of heart disease, etc. (e.g., see JAMA 1989; 262: 2395). Others of the studies in the meta-analysis also controlled for depression, mobility, chronic diseases, BMI, alcohol, education, diabetes, early parental mortality, and even red meat consumption — though it varied from study to study. The power of this paper is that it combines many studies with many participants showing mortality benefit from lower amounts of physical activity, and in that way gets a bigger picture of the results than a single study can. But, as with all observational studies, are there unanticipated confounders?? (i.e., are there other factors not taken into account which predispose some people to have less activity but put them at higher mortality risk? Perhaps they have unanticipated neurologic conditions? Or have they fallen and are afraid to do exercise, but are at higher mortality risk because of a condition predisposing them to fall?)
- But, despite this significant limitation (i.e., not having a randomized controlled study with allotment of individuals to differing levels of exercise and seeing what happens), perhaps the strongest message we can give patients is: exercise is good for you and you should do whatever you can (the concern is that by prescribing/insisting on too much exercise for an individual, some people end up doing nothing). I have had success in just getting people to walk 15-20 minutes/day (15 minutes of walking/day is the midpoint of the low activity group, with 250 MET-min), and some of them are able to increase that over time. And many people actually feel better after doing exercise…
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