It is interesting to see a study in which exercise failed to improve memory function in older adults, given the sizable number of studies showing that it does help. One possibility is that intensity of exercise matters. In general, however, the literature leans in the direction of exercise slowing cognitive decline. Yet no outcome in research is so guaranteed that there will be a complete absence of studies in which it fails to show up in the data; this is one of the challenges inherent in following the output of the scientific community.
A large study that focused on whether exercise and mindfulness training could boost cognitive function in older adults found no such improvement following either intervention. The researchers studied 585 adults ages 65 through 84. None had been diagnosed with dementia, but all had concerns about minor memory problems and other age-related cognitive declines.
All study participants were considered cognitively normal for their ages. The researchers tested them when they enrolled in the study, measuring memory and other aspects of thinking. They also conducted brain-imaging scans. The participants were randomly assigned to one of four groups: a group in which subjects worked with trained exercise instructors; a group supervised by trained experts in the practice of mindfulness; a group that participated in regular exercise and mindfulness training; and a group that did neither, but met for occasional sessions focused on general health education topics. The researchers conducted memory tests and follow-up brain scans after six months and again after 18 months.
At six months and again at 18 months, all of the groups looked similar. All four groups performed slightly better in testing, but the researchers believe that was due to practice effects as study subjects retook tests similar to what they had taken previously. Likewise, the brain scans revealed no differences between the groups that would suggest a brain benefit of the training.