Incidence and risks of dementia in Japanese women: Radiation Effects Research Foundation Adult Health Study

Background: Although dementia has a great impact on public health, there are few reports on dementia incidence and risk factors for Asian populations. Objectives: To determine incidence and risk factors of dementia, Alzheimer disease (AD), and vascular dementia (VaD) among Japanese women. Methods: Between 1992 and 1996,1637 non-demented women aged >= 60 years were followed for an average of 5.9 years in RERF's Adult Health Study. Dementia diagnoses were made during biennial health examinations using a two-phase procedure. DSM IV criteria were used for diagnosing dementia, NINCDS-ADRDA for AD, and NINDS-AIREN for VaD. Potential risk factors were analyzed using Poisson regression analysis. Results: 161 cases of dementia (109 of AD and 56 of VaD, based on individual criteria) were newly diagnosed. Incidence increased dramatically with age, especially for AD. Probable AD decreased with increasing education level. Probable VaD was significantly associated with hypertension and stroke. Age at menopause did not show any effect on dementia. All dementia and probable AD were significantly associated with grip strength. Conclusions: AD is predominant in dementia incidence among Japanese women. Modification of stroke risk factors and improvement of physical fitness may help prevent dementia. (C) 2009 Elsevier B.V. All rights reserved.