Sex Differences in the Association Between Body Mass Index and Dementia Risk in Community-Dwelling Japanese People Aged 40–74 Years

Article type: Research Article

Authors: Zakharova, Alena^{a; b; 1} | Kitamura, Kaori^{a; 1} | Watanabe, Yumi^a | Kabasawa, Keiko^c | Takahashi, Akemi^d | Saito, Toshiko^e | Kobayashi, Ryosaku^d | Oshiki, Rieko^d | Takachi, Ribeka^f | Tsugane, Shoichiro^g | Yamazaki, Osamu^h | Watanabe, Keiⁱ | Nakamura, Kazutoshi^{a; *}

Affiliations: [a] Division of Preventive Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan | [b] Department of Public Health and Health Care, Krasnoyarsk State Medical University named after Professor V.F. Voyno-Yasenetsky, Krasnoyarsk, Russia | [c] Department of Health Promotion Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan | [d] Department of Rehabilitation, Niigata University of Rehabilitation, Niigata, Japan | [e] Department of Health and Nutrition, Niigata University of Health and Welfare, Niigata, Japan | [f] Department of Food Science and Nutrition, Nara Women’s University Graduate School of Humanities and Sciences, Nara, Japan | [g] National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition, Tokyo, Japan | [h] Niigata Prefectural Government, Niigata, Japan | [i] Department of Orthopedic Surgery, Niigata University Medical and Dental Hospital, Niigata, Japan

Correspondence: [*] Correspondence to: Kazutoshi Nakamura, Division of Preventive Medicine, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan. E-mail: [email protected]; ORCID: 0000-0002-8618-7632.

Note: [1] These authors contributed equally to this work.

Abstract: Background:The association between body mass index (BMI) and dementia risk is heterogeneous across age groups and might be influenced by sex. Objective:This study aimed to clarify sex differences in the association between BMI and dementia risk in community-dwelling people. Methods:This cohort study with an 8-year follow-up targeted 13,802 participants aged 40–74 years at baseline in 2011–2013. A self-administered questionnaire requested information on body size, including height, weight, and waist circumference (the values of which were validated by direct measurement), socio-demographics, lifestyle, and disease history. BMI was calculated and categorized as < 18.5 (underweight), 18.5–20.6 (low-normal), 20.7–22.6 (mid-normal), 22.7–24.9 (high-normal), 25.0–29.9 (overweight), and≥30.0 kg/m2 (obese). Incident cases of dementia were obtained from the long-term care insurance database. A Cox proportional hazards model was used to calculate multivariable-adjusted hazard ratios (HRs). Results:The mean age of participants was 59.0 years. In men, higher BMI was associated with lower dementia risk (fully-adjusted p for trend = 0.0086). In women, the association between BMI and dementia risk was U-shaped; the “underweight,” “low-normal,” and “overweight” groups had a significantly higher risk (fully-adjusted HR = 2.12, 2.08, and 1.78, respectively) than the reference (“high-normal” group). These findings did not change after excluding dementia cases which occurred within the first four years of the follow-up period. Conclusion:Overweight/obese women, but not men, had an increased risk of dementia, suggesting that sex differences in adiposity might be involved in the development of dementia.

Keywords: Alzheimer’s disease, body mass index, cohort study, dementia, risk factor, sex difference, waist circumference

DOI: 10.3233/JAD-230294

Journal: Journal of Alzheimer's Disease, vol. 94, no. 3, pp. 949-959, 2023