There is a high priority on identifying preventive behaviors that can reduce rates of Alzheimer’s Disease and other dementias. Non-medical interventions to prevent or delay dementia onset may have tremendous impact on quality of life and the reduction of health care costs. While research suggests that maintaining cardiovascular health may be the most promising way to reduce dementia risk, there is a lack of large-scale longitudinal research on the long-term impact of cardiovascular health on dementia onset. The Annals of Internal Medicine recently published a long-term observational study that addresses this gap and suggests that a high level of cardiovascular fitness in midlife may be protective against dementia.
Participants in the study were patients at a preventive medicine clinic in Texas, which opened in 1970. Each patient’s first clinic visit entailed a baseline fitness examination which included an objective treadmill-based test of cardiorespiratory fitness, as well as a general health screening. Because examination results from the clinic are available as far back as 1971, the clinic provided a large source of relevant longitudinal data. Almost 30,000 patients at the clinic were community-dwelling adults whose first visit to the clinic came before they turned 65 years of age, and who agreed to participate in a longitudinal study on preventive health behaviors.
The researchers were able to obtain Medicare administrative claims data on 19,458 of the initial group of patients, who comprise the sample population of the study. For purposes of this study, researchers excluded clinic visitors who had a stroke, heart attack, or diagnosis of dementia at baseline. The average age at baseline (i.e., the first clinic visit) for study participants was around 50, and, for 95 percent of this sample, at least nine years had passed between their baseline examination and their entry into Medicare. The average time between screening and most recent Medicare claim data was around 24 years. Thus, the researchers were able to obtain relevant data on long-term medical associations with midlife physical fitness.
Another advantage of the study was the use of objective measures of physical fitness. Many studies that explore the association between physical fitness and cognitive decline use participants’ self-reports of fitness or of physical activity, which are subject to bias and inconsistency. This study used an objective measure of physical fitness that has a plausible connection to neurological health.
The findings supported the researchers’ hypothesis that a high level of midlife physical fitness would be associated with a lower risk of dementia. The fittest 25 percent of participants (based on their baseline treadmill assessment of cardiorespiratory health), when statistically adjusting for relevant variables such as age, education, and other relevant factors such as alcohol, had a reduced risk of dementia onset, between about one-half to three-fourths the risk of less fit study participants. While this study doesn’t prove a causal relationship between fitness and dementia, future research building on these findings may show that physical fitness may be a way to minimize dementia risk.
DeFina LF, Willis BL, Radford NB, et al. The association between midlife cardiorespiratory fitness levels and later-life dementia. Annals of Internal Medicine. (2013). 158:162–168.