Since the advent of low-cost, small accelerometers of the sort found in every modern mobile phone, it has been possible to gather much better data on the degree to which people are active or inactive. One of the findings that has emerged in epidemiological studies of exercise in older people is that even modest levels of activity appear to have a sizable correlation with health. This means puttering around in the kitchen or the garden, walking around the house little more, and the like. In the bigger picture, it is very reasonable to believe that exercise causes better health; this is proven in animal studies, even though the best that most human studies can do is to show an association. Exercise, like any treatment, has a dose-response curve of effects on health. Evidence in humans suggests that there is a big jump in benefits when moving from very low activity to merely low activity.
Older adults who move more than average, either in the form of daily exercise or just routine physical activity such as housework, may maintain more of their memory and thinking skills than people who are less active than average, even if they have brain lesions or biomarkers linked to dementia. "We measured levels of physical activity in study participants an average of two years prior to their deaths, and then examined their donated brain tissue after death, and found that a more active lifestyle may have a protective effect on the brain. People who moved more had better thinking and memory skills compared to those who were more sedentary and did not move much at all."
The study assessed 454 older adults; 191 had dementia and 263 did not. All participants were given physical exams and thinking and memory tests every year for 20 years. The participants agreed to donate their brains for research upon their deaths. The average age at death was 91 years. At an average of two years before death, researchers gave each participant an activity monitor called an accelerometer. The wrist-worn device monitored physical activity around the clock, including everything from small movements such as walking around the house to more vigorous activity like exercise routines. Researchers collected and evaluated seven days of movement data for each participant and calculated an average daily activity score. The results were measured in counts per day, with an overall average of 160,000 counts per day.
People without dementia had an average of 180,000 counts per day, and people with dementia had an average of 130,000 counts per day. Researchers found that higher levels of daily movement were linked to better thinking and memory skills. The study also found that people who had better motor skills - skills that help with movement and coordination - also had better thinking and memory skills. For every increase in physical activity by one standard deviation, participants were 31 percent less likely to develop dementia. For every increase in motor ability by one standard deviation, participants were 55 percent less likely to develop dementia.