From the Department of Psychology and Logopedics (V.R., J.L., K.R.), University of Helsinki; Folkhälsan Research Center (V.R., J.L., J.G.E.); National Supervisory Authority of Welfare and Health (M.H.), Department of Health Care Supervision; Center of Military Medicine (M.H.); Division of Welfare and Health Promotion (E.K.), Department of Chronic Disease Prevention, Diabetes Prevention Unit, National Institute for Health and Welfare; Hospital for Children and Adolescents (E.K.), Helsinki University Central Hospital and University of Helsinki; Department of Obstetrics and Gynaecology (E.K.), Oulu University Hospital and University of Oulu; Department of General Practice and Primary Health Care (J.G.E.), University of Helsinki and Helsinki University Hospital; and Vasa Central Hospital (J.G.E.), Finland. ville.rantalainen@helsinki.fi.
To test if the Finnish Defence Forces Basic Intellectual Ability Test scores at 20.1 years predicted risk of organic dementia or Alzheimer disease (AD).
Dementia was defined as inpatient or outpatient diagnosis of organic dementia or AD risk derived from Hospital Discharge or Causes of Death Registers in 2,785 men from the Helsinki Birth Cohort Study, divided based on age at first diagnosis into early onset (1.69, 95% confidence interval [CI] 1.01-2.63) scores predicted higher early-onset any dementia risk across the statistical models; arithmetic and visuospatial ability scores were similarly associated with early-onset any dementia risk, but these associations weakened after covariate adjustments (HR per 1 SD disadvantage >1.57, 95% CI 0.96-2.57). All associations were rendered nonsignificant when we adjusted for participant's education. Cognitive ability did not predict late-onset dementia risk.
These findings reinforce previous suggestions that lower cognitive ability in early life is a risk factor for early-onset dementia.