ORIGINAL ARTICLE: EPIDEMIOLOGY, CLINICAL PRACTICE AND HEALTH Association between body composition parameters and risk of mild cognitive impairment in older Japanese adults Seongryu Bae, 1 Hiroyuki Shimada, 1 Hyuntae Park, 2 Sangyoon Lee, 1 Hyuma Makizako, 1 Takehiko Doi, 1 Daisuke Yoshida, 3 Kota Tsutsumimoto, 1 Yuya Anan 4 and Takao Suzuki 5 1 Department of Preventive Gerontology, Center for Gerontology and Social Science, National Center for Geriatrics and Gerontology, Obu, Aichi, 3 Department of Physical Therapy, Faculty of Rehabilitation, Kyushu Nutrition Welfare University, Kitakyushu, Fukuoka, 4 Department of Nutritional Health, Faculty of Wellness Studies, Kwassui Women’ s University, Nagasaki, 5 Research Institute of Aging and Development, J.F. Oberlin University, Tokyo, Japan; and 2 Department of Health Care Science College of Health Sciences, Dong-A University, Busan, Korea Aim: The aim of the present study was to investigate the association between various body composition parameters and the risk of mild cognitive impairment (MCI) in older Japanese adults, as well as potential sex-related differences in the risk of MCI. Methods: Participants underwent cognitive tests, and were divided into 840 participants with MCI (mean age 71.9 ± 5.5 years) and 1740 without MCI (mean age 71.3 ± 5.2 years). Body composition parameters were measured using a bioelectrical impedance analyzer. Multiple logistic regression analysis was then carried out to examine the associations between body composition parameters and risk of MCI. Results: After adjusting for confounding factors, those in the lowest quartile for fat-free mass had a higher risk of MCI than those in the highest quartile (men: odds ratio [OR] 1.96, 95% confidence interval CI 1.24–3.10; women: OR 1.49, 95% CI 1.01–2.19). Loss of muscle mass in the upper (OR 2.17, 95% CI 1.40–3.37) and lower (OR 1.99, 95% CI 1.25–3.15) limbs was associated with a higher MCI risk in men. However, only loss of muscle mass in the lower limbs was associated with a higher MCI risk (OR 1.61, 95% CI 1.06–2.44) in women. No associations were found between obesity measures and MCI. Conclusions: We found that loss of fat-free mass was associated with MCI in older adults, regardless of sex. We also found that appendicular muscle mass was more closely associated with MCI in men than in women. These results suggest that the association between appendicular muscle mass and MCI might have different underlying mechanisms based on sex. Geriatr Gerontol Int 2017; ••: ••–••. Keywords: aging, body composition parameters, fat-free mass, fat mass, mild cognitive impairment. Introduction Age-related changes in body composition are recognized as a potentially modifiable factor associated with decreased physical function, disability and mortality. 1,2 Changes in body composition might also be associated with cognitive decline, Alzheimer’ s disease (AD) and brain atrophy, sug- gesting that these two entities could share underlying pathophysiological pathways. 3,4 Mild cognitive impairment (MCI) is a syndrome de- fined as a transitional state between normal aging and dementia. Individuals with MCI have a higher risk of pro- gression to dementia within 5 years; however, more than half remain stable or return to a normal state. 5 Therefore, detection of MCI at an early stage is important for preven- tion. Associations have been found between lower late-life body mass index (BMI) and MCI, suggesting that low BMI is a potential risk factor for MCI. 6 In addition, associations have been reported between low weight or BMI and an increased risk of incident dementia and AD in longitudinal studies of older adult populations, suggesting that low weight or BMI might be a risk factor for, or an early sign of, dementia. 7 However, most studies regarding body composition in dementia, AD and MCI are limited by their use of relatively non-specific measures of body composition – such as total bodyweight or BMI – rather than more specific measures, such as fat mass (FM) or muscle mass (MM). Accepted for publication 17 January 2017. Correspondence: Dr Seongryu Bae PhD, Department of Preventive Gerontology, National Center for Geriatrics and Gerontology, 7-430 Morioka, Obu, Aichi 474-8511, Japan. Email: bae.seongryu@gmail. com © 2017 Japan Geriatrics Society doi: 10.1111/ggi.13018 | 1 Geriatr Gerontol Int 2017