A fair amount of interesting research on the topic of exercise and aging passes by every month. Most is not really worth commenting on here, other than to reinforce the point that there is a very, very large body of evidence to link regular exercise with improved long-term health and reduced mortality. Since I did note a few items worth reading recently, I thought I'd bundle them together for today's post as just such a reminder. In human studies the evidence for exercise tends to be a matter of correlation more often than causation, but the corresponding animal studies, in which researchers can put individuals into groups by level of exercise and observe the results across the life span of a cohort, leave no doubt as to the benefits provided by regular exercise. The results over the long term remain better than anything a basically healthy individual can obtain from medical science today, say to say, though that statement won't be true for many more years given the progress being made towards rejuvenation therapies. You can't exercise your way to ensuring a life span of 100 years, it isn't that large of an effect, but the benefits that can be realized are available, reliable, and free. It makes sense to take advantage of them.
The high level summary of the present research community consensus on the health benefits of exercise is that it, like many things in health and medicine, appears to have a U-shaped dose-response curve with the 80/20 point somewhere around about or a little above the standard recommendations for half an hour to an hour a day of moderate aerobic exercise. While elite athletes are shown to live a few years longer than the rest of us, it remains unclear as to whether that is due to the large amount of physical exercise or due to the fact that more robust people - who would live longer anyway - tend to have a better shot at succeeding in the world of professional athletics. At the other end of the dose-response curve, the growing use of accelerometers in studies has demonstrated that even modest levels of exercise, such as infrequent gardening or cleaning or walking, have noticeable correlations with health and mortality. More is better, however, and there is a pretty clear difference in life expectancy between those who manage regular moderate exercise and those who remain sedentary. Given that a radical change in the state of medicine lies ahead, the transition from not treating the causes of aging to actually and effectively repairing those causes, it makes sense to eke out extra years of healthy life, to increase the odds of living to take advantage of the rejuvenation biotechnologies yet to come.
Researchers, it is hoped, will one day find a miracle cure for all kinds of diseases. Yet over and over again it has been shown that even if it takes a little more effort than swallowing a little pill, exercise is an excellent preventive and curative treatment for many diseases. A new study shows that even low physical fitness, up to 20% below the average for healthy people, is sufficient to produce a preventive effect on most of the risk factors that affect people with cardiovascular disease. To measure the impact of physical fitness on heart disease risk factors, the researchers selected 205 men and 44 women with heart disease, including coronary artery disease, stroke, congestive heart failure, and heart valve disease, and had them undergo a stationary bike stress test to determine their fitness level. The results showed that normal physical fitness, even up to 20% below the population average, is sufficient to have a preventive effect on five of the eight risk factors affecting people with cardiovascular disease - abdominal circumference, diabetes, hypertension, obesity, and excess weight. Normal physical fitness means having the physical fitness of a person of the same weight, height, sex, and age, and who is disease-free. The easiest way to achieve this is to follow the recommendations of the World Health Organization - 150 minutes per week of moderate exercise or 75 minutes of vigorous exercise.
More and more studies confirm that sitting is bad for our health. It increases the likelihood of developing cardiovascular disease and other lifestyle-related illnesses such as diabetes. Some studies have estimated that being sedentary kills as many people as smoking. The average adult in the Western world sits between 9 and 11 hours a day, a number that only increases as we age. In fact, in a study in older adults just published researchers found that the least sedentary third of their study participants still spent between 12 and 13 hours in sedentary behavior, while the most sedentary of the elders in the study were sedentary for up to 15 hours a day.
But how does being fit affect the health risk associated with a sedentary lifestyle, especially in older adults, who are the most likely to be sedentary? The researchers found that older women and men in the most sedentary group were correspondingly 83% and 63% more likely to have risk factors for cardiovascular disease compared to women and men who were least sedentary. But when the researchers took fitness into account, they found that having high age-specific fitness (in this case, being among the fittest 40%) reduced the likelihood of having cardiovascular risks factors posed by extended time spent being sedentary. However, no such effect was found in those who were physically active without being fit. "Our Western lifestyles necessarily involve a lot of sitting, and we spend more and more time sitting on average as we age. But our findings show that being fit plays an important part in successful ageing and may lend protection against the negative health effects of being sedentary."
Mild Cognitive Impairment (MCI) defines people who have noticeably reduced cognitive abilities such as reduced memory but are still able to live independently, and is a precursor to Alzheimer's disease. Findings from the Study of Mental and Resistance Training (SMART) trial show, for the first time, a positive causal link between muscle adaptations to progressive resistance training and the functioning of the brain among those over 55 with MCI. "What we found in this follow up study is that the improvement in cognition function was related to their muscle strength gains. The stronger people became, the greater the benefit for their brain." SMART was a randomised, double-blind trial involving 100 community-dwelling adults with MCI, aged between 55 and 86. These new findings reinforce research from the SMART trial, whereby MRI scans showed an increase in the size of specific areas of the brain among those who took part in the weight training program. These brain changes were linked to the cognitive improvements after weight lifting.
To assess the efficacy of a progressive aerobic exercise training program on cognitive and everyday function among adults with mild subcortical ischemic vascular cognitive impairment (SIVCI), this was a proof-of-concept trial comparing a 6-month, thrice-weekly, progressive aerobic exercise training program (AT) with usual care plus education on cognitive and everyday function with a follow-up assessment 6 months after the formal cessation of aerobic exercise training. Seventy adults randomized to aerobic exercise training or usual care were included in intention-to-treat analyses. At the end of the intervention, the aerobic exercise training group had significantly improved Alzheimer's Disease Assessment Scale cognitive subscale (ADAS-Cog) performance compared with the usual care plus education group (-1.71 point difference); however, this difference was not significant at the 6-month follow-up (-0.63 point difference). There were no significant between-group differences at intervention completion and at the 6-month follow-up in EXIT-25 or ADCS-ADL performance. Examination of secondary measures showed between-group differences at intervention completion favoring the AT group in 6-minute walk distance (30.35 meter difference) and in diastolic blood pressure (-6.89 mm Hg difference). This study provides preliminary evidence for the efficacy of 6 months of thrice-weekly progressive aerobic training in community-dwelling adults with mild SIVCI, relative to usual care plus education.