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Are Low Levels of Physical Activity Significant in Health and Longevity?

Mapping the dose-response curve for exercise, its effects on health and life expectancy, is of great interest to the research community. Given the significant time and effort required to make progress via epidemiological studies, this mapping will no doubt still be an ongoing concern even after the first rejuvenation therapies are widely available. The best we can expect from present day data on physical activity in humans are broad conclusions, such as that regular moderate exercise is good for you, while being sedentary is not, and a highlighting of areas of uncertainty.

One of these areas of uncertainty is the question of low level activity: walking around the house, gardening, shopping, and so forth. Things that don't rise to the level of deliberate physical exercise. Do these activities have a noticeable impact on health and longevity? Is it a case of more is better? Prior to the creation of small accelerometers, of the sort found inside every mobile device these days, there was simply no way to tell. Studies used self-reported data, which is unreliable enough to obscure small differences. With accelerometers, the first studies appeared to suggest that yes, low levels of exercise do correlate with better health in later life. Human epidemiology can rarely do more than point out correlations, but animal studies of exercise definitively show causation of improved health. There is every reason to believe that the observed human data is due to exercise causing improved health.

Not all accelerometer studies produce results that support the hypothesis that benefits arise from low levels of physical activity, however. A paper from earlier this year reported finding no association between low level physical activity and mortality rate, for example. This is a slow-moving part of the field, in which one has to weigh the balance of many studies carried out over a decade or more. At the present time the scales tip towards casual activity providing a modest benefit; more papers arrive with conclusions akin to the one noted here. Still, by the time all is said and done, a couple of decades from now at the present pace, degree of exercise will be nowhere near as influential on your health as whether or not you have access to rejuvenation therapies after the SENS model of periodic damage repair. It is still a good plan to exercise, as it would be foolish to turn down highly reliable, free benefits to health, even if they are modest in comparison to the rewards the future will bring.

For older women, every movement counts, new study finds

Folding your laundry or doing the dishes might not be the most enjoyable parts of your day. But simple activities like these may help prolong your life, according to the findings of a new study in older women. In the U.S. study of more than 6,000 white, African-American and Hispanic women ages 63 to 99, researchers reported significantly lower risk of death in those who were active at levels only slightly higher than what defines being sedentary. Women who engaged in 30 minutes per day of light physical activity - as measured by an accelerometer instead of a questionnaire - had a 12 percent lower risk of death. Women who were able to do a half-hour each day of moderate to vigorous activity had a 39 percent lower mortality risk.

For the age group in this study, light physical activities include regular chores such as folding clothes, sweeping the floor or washing the windows. Activities like these account for more than 55 percent of how older people spend their daily activity. Moderate to vigorous activities would be brisk walking or bicycling at a leisurely pace. The bottom line? "Doing something is better than nothing, even when at lower-than-guideline recommended levels of physical activity."

Even when researchers simultaneously accounted for the amount of each type of activity (light and moderate-to-vigorous) a woman did, they still observed significantly lower mortality associated with each time, independently of the other. "Current public health guidelines require that physical activity be of at least moderate or higher intensity to confer health benefits. Our study shows, for the first time in older women, that health is benefitted even at physical activity levels below the guideline recommendations. The mortality benefit of light intensity activity extended to all subgroups that we examined, and was similar for women younger than 80 compared to women over the age of 80. It was similar across racial/ethnic backgrounds, and among obese and non-obese women. Perhaps most importantly for this population, the mortality benefit was similar among women with high and low functional ability."

Accelerometer-Measured Physical Activity and Mortality in Women Aged 63 to 99

Age-related deterioration in health is associated with a reduction in physical activity (PA). U.S. and international guidelines on PA and public health recommend that healthy older adults perform at least 2.5 hours/week of moderate-intensity or 1.25 hours/week of vigorous-intensity aerobic PA for health benefits, a target that few older U.S. adults meet, often because they are not capable of engaging in moderate- to vigorous-intensity PA (MVPA). Substantially lower all-cause mortality risk is associated with relatively high MVPA levels (3-5 times guideline recommended) assessed using questionnaires. The extent to which this extends to older adults is unclear.

Typically, self-reported activity explains only 10% to 20% of the variance in device-measured PA. PA misclassification is large in older adults, especially for light-intensity PA, which these individuals commonly perform but is currently not recommended for public health. Use of accelerometers to measure PA is novel in prospective studies on older adults and provides the ability to calibrate the effect of PA much better than with self-report, especially for light-intensity PA. We examined associations between mortality and accelerometer-measured PA using age-relevant intensity cutpoints in older women of various ethnicities.

The results support the hypothesis that higher levels of accelerometer-measured PA, even when below the moderate-intensity threshold recommended in current guidelines, are associated with lower all-cause and CVD mortality in women aged 63 to 99. Our findings expand on previous studies showing that higher self-reported PA reduces mortality in adults aged 60 and older, specifically in older women, and at less than recommended amounts. Moreover, our findings challenge the conclusion of recent meta-analyses that MVPA, measured by to self-report, is required to offset mortality risk in adults.

First, absolute rates of all-cause and cardiovascular disease mortality were at least 50% lower in cohort members in the middle tertile of each PA exposure than in those in the lowest tertile. This is particularly impressive when considering the small mean differences between these tertiles of 50 minutes/day for low light-intensity PA, 33 minutes/day for high light-intensity PA, and 20 minutes/day for MVPA. Use of accelerometers enhanced accurate quantification of such small differences in usual daily PA, which is not possible using questionnaire assessments. Small increases in daily PA, which older adults can achieve, could have a substantial effect on mortality in later life. Even in the oldest cohort members, ages 80-89 and ≥90 years, absolute rates of all-cause mortality were 44% and 15% lower, respectively, when comparing the middle and lowest total PA tertile.

Comments

A BYU study of exercise published in May, 2017 titled High levels of exercise linked to 9 years of less aging at the cellular level. The study looked at telomere length and found longer telomeres (more base pairs) in those who had the most exercise, while no difference was found in telomere lengths of those with low levels of exercise and sedentary individuals.

Posted by: Biotechy at November 21st, 2017 10:03 AM

Is it possible that better health allowed the longer-lived cohort to do, or want to do, these activities, rather than the activities causing the longevity?

Posted by: Tom Schaefer at November 21st, 2017 12:17 PM

@Tom Schaefer: That is always the question for association studies. Animal studies provide firm evidence to show that exercise improves health. Does that hold up in humans? It should. That doesn't rule out some degree of causation in the other direction, but establishing that degree is tough. The few studies that can talk about causation in humans have backed up the animal studies.

Posted by: Reason at November 21st, 2017 12:24 PM

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