Is Midlife Cardiovascular Fitness Associated with Reduced Risk for Dementia?

BACKGROUND AND PURPOSE:

• Multiple studies have reported an association between physical activity and decreased risk of dementia and preserved cognitive function
• Research is limited by self-reporting of physical activity
  • Improved cognitive function may be related to social interaction rather than actual physical fitness
• Hörder et al. (Neurology, 2018) tracked dementia incidence for 44 years to determine whether there is an association between midlife cardiovascular fitness and decreased risk for dementia

METHODS:

• Population-based sample of women aged 38 to 60 years
• Data derived from prospective Population Study of Women (PPSW), begun in 1968
• Women were admitted to an exercise test
• A stepwise-increased maximal ergometer cycling test (until exhaustion) to evaluate cardiovascular function was used, under physician supervision
• Fitness Description: Crude peak workload into
  • Low: ≤80W or interrupted at submaximal workload)
  • Medium (88–112W)
  • High(≥120W)
• Follow-up tests for dementia were conducted in 1974, 1980, 1992, 2000, 2005, and 2009
• Dementia was diagnosed according to DSM-III-R criteria on the basis of information from neuropsychiatric examinations, informant interviews, hospital records, and registry data up to 2012
• Socioeconomic, lifestyle, and medical confounders were adjusted for in the cox regression test

RESULTS:

• Data was collected from 1,462 women; the symptomatic cardiovascular subgroup consisted of 191 woman
  • 29 were 38 years
  • 41 were 46 years
  • 37 were 50 years
  • 47 were 54 years
  • 37 were 60 years
• Compared to medium fitness (referent population), high cardiovascular fitness was associated with significantly reduced risk of dementia
  • High fitness: Hazard ratio (HR) 0.12 (95% CI, 0.03–0.54)
  • Low fitness: HR 1.41 (95% CI, 0.72–2.79)
• High fitness delayed age at dementia onset by 9.5 years and time to dementia onset by 5 years, compared to medium fitness
• Based on the peak workload, the cumulative incidence of all-cause dementia was 32% for low fitness, 25% for medium fitness, and 5% for high fitness

CONCLUSION:

• Among Swedish women, high cardiovascular fitness in midlife was correlated with reduced risk of subsequent dementia
• High compared to medium fitness decreased the risk of dementia by 88%
• Fitness and physical activity are not identical and the former may have an underlying genetic component
• Findings demonstrate a strong association between physical fitness and dementia but are associative and not causal
• Future areas of study include understanding the underlying mechanisms
• The authors state

The risk reduction of high fitness on dementia was stronger for the crude peak workload than for peak workload/body weight. This is similar to studies on all-cause mortality in which obese fit individuals have a mortality risk similar to that of normal-weight fit individuals. This highlights the need for fitness-driven, rather than weight loss–driven, approaches.

Learn More – Primary Sources:

Midlife cardiovascular fitness and dementia: A 44-year longitudinal population study in women