Quite a few studies on physical activity and mortality rate have been published in the past few weeks. They lean towards supporting the hypothesis that low levels of activity are still beneficial to some degree in older individuals. The benefits scale up as activity becomes more intense, but there isn't a threshold that must be hit in order to obtain at least some improvement in health and reduction in mortality rate. The research here is another example of this sort of study outcome. Note that human studies generally show correlations, not causation. Corresponding animal studies of exercise and health that do prove causation are the reason why we can be fairly confident that exercise causes better health.
This study compared the association between different levels of physical activity and the risk of cardiovascular disease in elderly to middle-aged individuals. "We know that regular physical activity has major health benefits. Healthy adults are advised to do at least 150 minutes a week of moderate intensity or 75 minutes a week of vigorous intensity aerobic exercise to reduce their risk of cardiovascular disease. These recommendations are based primarily on research in middle-aged adults and we wanted to know whether regular physical activity yields comparable cardiovascular health benefits in elderly people."
The study included 24,502 adults aged 39 to 79 years who participated in the European Prospective Investigation into Cancer (EPIC) Norfolk cohort, a prospective population study that is part of the ten-country collaboration EPIC study. The cohort was primarily designed to assess dietary and other determinants of cancer, but data were also collected on determinants of cardiovascular disease. Participants were recruited between 1993 and 1997 from registries of general practices in the county of Norfolk, UK. On enrollment into the study, participants completed a health and lifestyle questionnaire, underwent a standardised physical examination and gave blood samples. Physical activity during work and leisure time was assessed with a questionnaire and participants were categorised as active, moderately active, moderately inactive and inactive.
Patients were followed up until 31 March 2015 for hospitalisation or death from cardiovascular events (coronary heart disease or stroke). Physical activity levels and time to cardiovascular events were investigated in three age categories: less than 55, 55 to 65 (middle-aged), and over 65 years of age (elderly). During a median follow-up of 18 years there were 5,240 cardiovascular disease events. In elderly participants, hazard ratios for cardiovascular events were 0.86, 0.87, and 0.88 in moderately inactive, moderately active and active people, respectively, compared to inactive people. In those aged 55-65 and less than 55 years, the associations were directionally similar, but not statistically significant.
"We observed an inverse association between physical activity and the risk of cardiovascular disease in both elderly and middle-aged people. As expected, there were more cardiovascular events in elderly participants, which could explain why the association only reached significance in this age category. Elderly people who were moderately inactive had a 14% reduced risk of cardiovascular events compared to those who were completely inactive. This suggests that even modest levels of physical activity are beneficial to heart health. Elderly people should be encouraged to at least do low intensity physical activities such as walking, gardening, and housework."