The study noted here can be added to the list of those that find modest activity to associate with reduced risk of cardiovascular disease risk in old people. This sort of finding is a comparatively recent development in epidemiology because it relies upon the use of accelerometers, of the sort found in every mobile device these days. Before the advent of low-cost accelerometers, studies of exercise and health relied on self-reporting, which is simply not accurate enough to identify effects resulting from low levels of everyday physical activity such as gardening, cleaning, and so forth. The current consensus on this sort of data is that activity causes health benefits and reduced mortality, not that people who are healthier tend to undertake more activity. This is based on a smaller amount of human data in which effects can be observed over years based on earlier levels of exercise, and on animal studies structured in order to prove that benefits derive from exercise.
Physical activity (PA) is known to improve health and decrease the risk of developing cardiovascular disease (CVD) in a variety of populations. However, less is known regarding the influence of habitual or daily PA in preventing cardiovascular events among older adults. In particular, data are lacking regarding the influence of daily PA on cardiovascular risk among older adults with mobility limitations that restrict the ability to engage in PA.
Although associations between the quantity of PA and cardiovascular risk factors have been reported in older adults, few have made these connections using objective measurements of PA. To date, most studies have relied on self-reported measures of PA, which commonly misclassify the volume and/or intensity of PA. Although PA has been shown to have an inverse relationship with cardiovascular risk factors and morbidity, it is unknown whether participation in activity reduces cardiovascular incidence in populations of older adults displaying habitually low levels of PA. Prospective studies to date have largely focused on increasing exercise participation, although formal exercise interventions have been insufficient in reducing the incidence of cardiac events in this population. However, few studies have utilized objective measurements using accelerometry to evaluate cardiovascular risk in older adults.
Our previous study found that every 25 to 30 minutes per day spent being sedentary - defined by less than 100 accelerometry counts per minute - was associated with a 1% higher predicted risk of myocardial infarction (MI) or coronary-related death. Conversely, daily time spent in activities registering 100 to 499 counts per minute was associated with lower predicted hard coronary heart disease risk. Every 30 to 35 minutes of inactivity in this range was also associated with a 1-mg/dL lower circulating high-density lipoprotein cholesterol concentration. Somewhat surprisingly, however, the mean intensity of daily activities was not associated with predicted cardiovascular risk in this population.
The cross-sectional nature of the prior study prevented the ability to draw causal inferences and provided only a projection of cardiovascular risk. Therefore, the overarching objective of the present study is to expand on these prior findings using longitudinal assessment of accelerometry-based PA patterns and the observation of cardiovascular events among this population. The primary finding of this study is that objective measurement of PA via accelerometry was significantly associated with incidence of cardiovascular events among older adults with limited mobility. The 1,590 study participants had an 11% lower incidence of experiencing a subsequent cardiovascular event per 500 steps taken per day based on activity data at baseline. At baseline, every 30 minutes spent performing activities ≥500 counts per minute were also associated with a lower incidence of cardiovascular events. Throughout follow-up (6, 12, and 24 months), both the number of steps per day and duration of activity ≥500 counts per minute were significantly associated with lower cardiovascular event rates.