Background Physical fitness has been associated with improved cognition in older age. We explored the associations between physical fitness and cognitive performance in healthy elderly and in individuals with dementia, taking into account the time since dementia diagnosis.
Methods Thirty elderly with dementia and 40 healthy controls completed a battery of standardised cognitive tests: Mini-Mental State Exam, Verbal Fluency, Prospective and Retrospective Memory Questionnaire, Clock Drawing and California Verbal Learning Test. Participants were grouped into high versus low levels of physical fitness (PF) based on their Physical Fitness Questionnaire scores.
A 2 × 2 between-subject multivariate analysis of covariance was used to evaluate the associations between PF levels and cognitive performance, adjusting for age, gender, education, occupation, head injury, internet use, brain training, and past levels of exercise. This was followed by a discriminant analysis to obtain a latent score of global cognitive functioning for each individual.
Results Healthy controls showed higher performance scores than individuals with dementia [Pillai’s Trace=0.61, F(10,49) = 7.75, p<0.001]. PF was associated with better cognitive performance [Pillai’s Trace=0.32, F(10,49) = 2.29, p<0.05] and this interacted with health status [Pillai’s Trace=0.30, F(10,49) = 2.12, p<0.05]. A significant discriminant analysis (Wilks λ=0.15, Chi-square=119.46, df=30, canonical correlation=0.87, p<0.001) extracted two discriminant functions that accounted for 95.4% of the variance, with the first function, reflecting global cognitive function, accounting for 83%. Reclassification using the canonical variables was 72.9% correct. Predicted values from the first discriminant function revealed that the interaction between health status and physical fitness was due to the latter improving global cognitive function in the dementia group [t(25)=2.90, p<0.01], but not in the healthy group (p>0.10). A regression analysis howed that although global functioning decreased with the number of years since dementia diagnosis [unstandardised regression coefficients (b)=−0.25, 95% CI (−0.47, −0.04), p<0.05], physical fitness was still associated with improved cognitive functioning [b=1.54, 95% CI (.49, 2.59)], with no interaction (p>0.05).
Conclusion Physical fitness was associated with improved cognitive functioning, particularly for individuals with dementia. This benefit was present independent of exercise history, age, or duration of dementia. These findings provide empirical support for the development of fitness programmes for dementia patients to offset the cognitive deterioration associated with the condition.
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