A possible association between waist-to-hip ratio and cognitive function among Japanese health-checkup participants: an exploratory cross-sectional study

The association between obesity-related indices and cognitive function remains unclear, particularly when considering muscle mass. In this cross-sectional study, we examined these associations in 263 Japanese adults aged ≥ 40 years who underwent a health-checkup (163 males and 100 females). Cognitive function was assessed using the Japanese version of the Montreal Cognitive Assessment (MoCA-J), and obesity-related indices included body mass index, waist-to-hip ratio (WHpR), and other measures of obesity.

Among males, WHpR was not significantly associated with MoCA-J scores after adjustment for age and lifestyle factors, whereas an inverse association emerged after additional adjustment for muscle mass. In the fully adjusted model, a higher WHpR was modestly associated with a lower MoCA-J score (standardised coefficient = − 0.17, P = 0.043) and higher odds of mild cognitive impairment (adjusted odds ratio = 1.08; 95% confidence interval, 1.00–1.16). No significant associations were observed among females.

These findings suggest a possible modest association between WHpR and cognitive vulnerability in males when muscle mass is taken into account. However, the WHpR × sex interaction was not statistically significant, and the associations in males were borderline. Accordingly, this pattern should be interpreted as exploratory and hypothesis-generating rather than as evidence of any confirmed sex-specific effect.

Trial registration: This study was registered in the University Hospital Medical Information Network (UMIN) Clinical Trial Registry on July 1, 2022 (UMIN000048056). We thank Takaaki Mori, Hiromi Hanano, Hiroki Yamaguchi, and Rina Matsumura at Doshisha University for their helpful advice. Furthermore, we thank the public health nurses at the Takeda Hospital Medical Examination Centre for assistance with sample collection and the members of the Satoh-Asahara Laboratories and Seaknit Biotechnology Co., Ltd. for helpful discussions.

We would also like to thank Editage (https://www.editage.jp/) for the English language review. This study was supported by Grant-in-Aid for Research Activity Start-up to KIk (25K24309), Scientific Research (C) to HK (JP24K14447), MT (JP22K07456), HY (JP25K14978) and (B) to NS-A (JP24K02363 and JP24H02835), by Grant-in-Aid for Exploratory Research to NS-A (JP22K19723), and by a grant for Longevity Sciences from the National Centre for Geriatrics and Gerontology to NS-A (24–1). The Smoking Research Foundation to NS-A, Japan Diabetes Society Junior Scientist Development Grant supported by Novo Nordisk Pharma Ltd. and Takeda Science Foundation to HK provided additional support.

The founders played no role in the study design, data collection and analysis, decision to publish or manuscript preparation. Faculty of Health and Sports Science, Doshisha University, 1-3 Tataramiyakodani, Kyotanabe, Kyoto, 610-0394, Japan Department of Endocrinology, Metabolism, and Hypertension Research, Clinical Research Institute, NHO Kyoto Medical Centre, 1-1 Fukakusa Mukaihata-cho, Fushimi-ku, Kyoto, 612-8555, Japan Kentaro Ikeue, Hisashi Kato, Hajime Yamakage, Masayo Iwasa, Izuru Masuda & Noriko Satoh-Asahara Department of Metabolic Research, Geroscience Research Centre, Research Institute, National Centre for Geriatrics and Gerontology, 7-430 Morioka-cho, Obu, 474-8511, Japan Hisashi Kato, Masashi Tanaka & Noriko Satoh-Asahara Department of Rehabilitation, Health Science University, 7187 Kodachi, Fujikawaguchiko-machi, Minamitsuru-gun, Yamanashi, 401-0380, Japan Faculty of Education, Saga University, 1 Honjo-machi, Saga, 840-8502, Japan Takeda Hospital Medical Examination Centre, Nihonseimei Kyoto Santetu Building, 608 Higashi Shiokoji-cho, Shiokoji-dori Nishinotoin Higashi-iru, Shimogyo-ku, Kyoto, 600-8216, Japan Diabetes Medicine, Mitsubishi Kyoto Hospital, 1 Katsura Gosho-machi, Nishikyo-ku, Kyoto, 615-8087, Japan Department of Diabetes and Endocrinology, Hospital, National Centre for Geriatrics and Gerontology, 7-430 Morioka-cho, Obu, 474-8511, Japan Division of Aging and Metabolic Research, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan The authors declare no competing interests. This study was approved by the Ethics Committee for Human Research at the National Hospital Organisation Kyoto Medical Centre (approval number: 21-082) and the Takeda Hospital Group (approval number: 2125).