Being Out of Shape in Midlife May Increase Risk for Dementia
Higher fitness during middle age is linked to lower dementia risk decades later.
Posted March 18, 2018
The results of a 44-year-long study suggest that women who were "super fit" at the age of 50 are at much lower risk for dementia as they get older in comparison to their less fit peers. This paper, “Midlife Cardiovascular Fitness and Dementia,“ was published March 14 in the online issue of Neurology, the medical journal of the American Academy of Neurology.
Notably, the "highly fit" middle-aged women in this study were 88 percent less likely to develop dementia than women who were only “moderately fit” during the same period of midlife.
Additionally, if a woman who was highly fit in midlife did develop dementia in older age, she wasn’t likely to develop the disease until age 90. However, women who were moderately fit during middle age and subsequently developed dementia, did so 11 years earlier, at the age of 79.
Over the 44 years of this study, five percent of the highly fit women developed dementia, compared to 32 percent of women with low fitness and 25 percent of moderately fit women.
"This indicates that negative cardiovascular processes may be happening in midlife that could increase the risk of dementia much later in life," first author Helena Hörder of the University of Gothenburg in Sweden said in a statement. "These findings are exciting because it's possible that improving people's cardiovascular fitness in middle age could delay or even prevent them from developing dementia."
The researchers sum up the main takeaway of this study in their conclusion: "Among Swedish women, a high cardiovascular fitness in midlife was associated with a decreased risk of subsequent dementia. Promotion of a high cardiovascular fitness may be included in strategies to mitigate or prevent dementia."
When drawing conclusions based on this study, it's important to remember that correlation does not automatically imply causation. As the authors make very clear in the study abstract, "Findings are not causal, and future research needs to focus on whether improved fitness could have positive effects on dementia risk and when during the life course a high cardiovascular fitness is most important."
"Limitations of the study include the relatively small number of women involved, all of whom were from Sweden, so the results may not be applicable to other populations," Hörder said. "Also, the women's fitness level was measured only once, so any changes in fitness over time were not captured. More research is needed to see if improved fitness could have a positive effect on the risk of dementia and also to look at when during a lifetime a high fitness level is most important."
How Were Study Participants Monitored During This 44-Year-Long Research?
In 1968, at the beginning of this study, a team of Swedish researchers recruited a population-based sample of 1,462 women ranging from 38 to 60 years of age. Six subsequent examinations for dementia based on DSM-III-R criteria, neuropsychiatric exams, informant interviews, hospital records, and other data were conducted in 1974, 1980, 1992, 2000, 2005, and 2009.
From the larger population-base of the study, a cohort of 191 women with an average age of 50 performed an ergometric exercise test to gauge how many watts of energy they could generate on a stationary bicycle before reaching physical exhaustion. The maximum wattage output of each participant before “conking out” represented her peak cardiovascular capacity.
When averaged, 103 watts was the bell curve peak for 50-year-old study participants. Of the 191 women who took the bicycle fitness test, 31 percent fell into the “low fitness” category marked by a maximum output of 80 watts or less. About 48 percent (98 women) fell into the “moderately fit” category and could pedal at a maximum output of between 80 to 120 watts. The “highly fit” cohort consisted of 40 women (about 21 percent) who maxed out at a peak workload of 120 watts or higher.
For anyone who is a cycling enthusiast: Using a "power tap" meter-like device to measure your wattage output on a road bike is a terrific way to gauge how hard you're working with each pedal stroke. The watts of energy you're exerting during aerobic exercise in relation to your VO2 max (an indicator of cardiovascular fitness) and target heart rate is an easy way to structure personalized cardio workouts that will optimize your cardiovascular fitness.
The latest research by Hörder et al. adds to a growing pile of empirical evidence that correlates higher levels of cardiorespiratory fitness across the human lifespan with a wide range of neuroprotective benefits such as better cognitive function and lower risk for dementia in old age.
If you are middle-aged, hopefully, the latest findings on the dementia-related benefits of being "super fit" in midlife will inspire you to seek moderate-to-vigorous physical activity (MVPA) more regularly.
As always, please use common sense and consult with your primary care physician before beginning any new exercise program or increasing the duration and/or intensity of your cardiovascular workouts.
Helena Hörder, Lena Johansson, XinXin Guo, Gunnar Grimby, Silke Kern, Svante Östling, Ingmar Skoog. "Midlife Cardiovascular Fitness and Dementia: A 44-year Longitudinal Population Study in Women." Neurology (First published: March 14, 2018) DOI: 10.1212/WNL.0000000000005290
Scott M. Hayes, Jasmeet P. Hayes, Victoria J. Williams, Huiting Liu, Mieke Verfaellie. “FMRI Activity During Associative Encoding Is Correlated with Cardiorespiratory Fitness and Source Memory Performance in Older Adults.” Cortex (2017) DOI: 10.1016/j.cortex.2017.01.002
Zaldy S. Tan, Nicole L. Spartano, Alexa S. Beiser, Charles DeCarli, Sanford H. Auerbach, Ramachandran S. Vasan, and Sudha Seshadri. “Physical Activity, Brain Volume, and Dementia Risk: The Framingham Study.” The Journal of Gerontology (2017) DOI: 10.1093/gerona/glw130