Objectives

This study investigated the association between perceived physical fitness at midlife, changes in perceived fitness during the three decades from mid- to late life, and dementia risk.

Design

Prospective cohort study.

Setting

Cardiovascular Risk Factors, Aging, and Incidence of Dementia (CAIDE) study.

Subjects

Subjects were selected from four independent, random samples of population-based cardiovascular surveys and were first examined in 1972, 1977, 1982, or 1987, when they were on average 50 years old. The CAIDE target population included 3,559 individuals. A random sample of 2,000 individuals still alive in 1997 was drawn for re-examinations (performed in 1998 and 2005–2008) that consisted of cognitive assessments, with 1,511 subjects participating in at least one re-examination. Dementia diagnoses were also confirmed from national registers for the entire target population.

Main outcome measure

All-cause dementia.

Results

Poor physical fitness at midlife was associated with increased dementia risk in the entire target population [hazard ratio (HR), 1.5; 95% confidence interval (CI), 1.1–2.0]. In participants, odds ratio (OR) was 2.0 (95% CI, 0.9–4.0). This association was significant in apolipoprotein E ε4 allele (APOEε4) non-carriers (OR, 4.3; 95% CI, 1.4–13.3), men (HR, 1.8; 95% CI, 1.1–3.0), and people with chronic conditions (HR, 2.9; 95% CI, 1.3–6.6). A decline in fitness after midlife was also associated with dementia (OR, 3.0; 95% CI, 1.7–5.1), which was significant among both men and women and more pronounced in APOEε4 carriers (OR, 4.4; 95% CI, 2.1–9.1).

Conclusions

Perceived poor physical fitness reflects a combination of biological and lifestyle-related factors that can increase dementia risk. A simple question about perceived physical fitness may reveal at-risk individuals who could benefit from preventive interventions.