Abstract
BackgroundPrevious studies have demonstrated that individual measures of fitness – such as reduced pulmonary function, slow walking speed and weak handgrip – are associated with an increased risk of dementia. Only a minority of participants included in these studies were aged over 80. The aim of this study was therefore to investigate the association between physical fitness and dementia in the oldest old.MethodsSubjects (n = 488) were enrolled in the Lothian Birth Cohort 1921 and aged 79 at baseline. Dementia cases arising after enrolment were determined using data from death certificates, electronic patient records and clinical reviews. Fitness measures included grip strength, forced expiratory volume in 1 s (FEV1) and walking speed over 6 m, measured at 79 years. Dementia risk associated with each fitness variable was initially determined by logistic regression analysis, followed by Cox regression analysis, where death was considered as a competing risk. APOE ε4 status, age, sex, height, childhood IQ, smoking, history of cardiovascular or cerebrovascular disease, hypertension and diabetes were included as additional variables. Cumulative incidence graphs were calculated using Aalen-Johansen Estimator.ResultsAlthough initial results indicated that greater FEV1 was associated with an increased risk of dementia (OR (odds ratio per unit increase) 1.93, p = 0.03, n = 416), taking into account the competing risk of mortality, none of the fitness measures were found to be associated with dementia; FEV1 (HR (hazard ratio per unit increase) 1.30, p = 0.37, n = 416), grip strength (HR 0.98, p = 0.35, n = 416), walking speed (HR 0.99, p = 0.90, n = 416). The presence of an APOE ɛ4 allele was however an important predictor for dementia (HR 2.85, p < 0.001, n = 416). Cumulative incidence graphs supported these findings, with an increased risk of dementia for APOE ɛ4 carriers compared with non-carriers. While increased FEV1 was associated with reduced risk of death, there was no reduction in risk for dementia.ConclusionsIn contrast to previous studies, this study found that lower fitness beyond age 79 was not a risk factor for subsequent dementia. This finding is not explained by those with poorer physical fitness, who would have been more likely to develop dementia, having died before onset of dementia symptoms.
Highlights
Previous studies have demonstrated that individual measures of fitness – such as reduced pulmonary function, slow walking speed and weak handgrip – are associated with an increased risk of dementia
Tests of lung function, walking speed and grip strength are frequently used to measure physical fitness. Such measures reflect the components of physical fitness described above, with lung function tests providing a measure of cardiorespiratory function, grip strength providing a measure of muscular strength and walking speed providing a measure of both muscular endurance and cardiorespiratory endurance
This study considers the participants of the Lothian Birth Cohort 1921 (LBC1921), who were recruited at age 79 years and have undergone follow-up for dementia into their 90s
Summary
Previous studies have demonstrated that individual measures of fitness – such as reduced pulmonary function, slow walking speed and weak handgrip – are associated with an increased risk of dementia. The aim of this study was to investigate the association between physical fitness and dementia in the oldest old. Physical fitness can reflect a person’s ability to undertake the physical activities required to achieve day-to-day function. In the investigation of associations between fitness and disease, test measures should reflect at least one of these components. Tests of lung function, walking speed and grip strength are frequently used to measure physical fitness. A latent trait representing physical fitness can be extracted from these variables which is significantly associated with non-pathological cognitive change in this cohort of older adults at age ~ 80 years [1]
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