Theresia Mina, Yik Weng Yew, Hong Kiat Ng, Nilanjana Sadhu, Gervais Wansaicheong, Rinkoo Dalan, Dorrain Yan Wen Low, Benjamin Chih Chiang Lam, Elio Riboli, Eng Sing Lee, Joanne Ngeow, Paul Elliott, Konstadina Griva, Marie Loh, Jimmy Lee, John Chambers, Lee Kong Chian School of Medicine (LKCMedicine), National Skin Centre, Tan Tock Seng Hospital, Khoo Teck Puat Hospital, National Healthcare Group Polyclinic, National Cancer Centre, and Institute of Mental Health
Background: Obesity and related metabolic disturbances including diabetes, hypertension and hyperlipidemia predict future cognitive decline. Asia has a high prevalence of both obesity and metabolic disease, potentially amplifying the future burden of dementia in the region. We aimed to investigate the impact of adiposity and metabolic risk on cognitive function in Asian populations, using an epidemiological analysis and a two-sample Mendelian Randomization (MR) study. Methods: The Health for Life in Singapore (HELIOS) Study is a population-based cohort of South-East-Asian men and women in Singapore, aged 30–84 years. We analyzed 8769 participants with metabolic and cognitive data collected between 2018 and 2021. Whole-body fat mass was quantified with Dual X-Ray Absorptiometry (DEXA). Cognition was assessed using a computerized cognitive battery. An index of general cognition ‘g’ was derived through factor analysis. We tested the relationship of fat mass indices and metabolic measures with ‘g’ using regression approaches. We then performed inverse-variance-weighted MR of adiposity and metabolic risk factors on ‘g’, using summary statistics for genome-wide association studies of BMI, visceral adipose tissue (VAT), waist-hip-ratio (WHR), blood pressure, HDL cholesterol, triglycerides, fasting glucose, HbA1c, and general cognition. Findings: Participants were 58.9% female, and aged 51.4 (11.3) years. In univariate analysis, all 29 adiposity and metabolic measures assessed were associated with ‘g’ at P < 0.05. In multivariable analyses, reduced ‘g’ was consistently associated with increased visceral fat mass index and lower HDL cholesterol (P < 0.001), but not with blood pressure, triglycerides, or glycemic indices. The reduction in ‘g’ associated with 1SD higher visceral fat, or 1SD lower HDL cholesterol, was equivalent to a 0.7 and 0.9-year increase in chronological age respectively (P < 0.001). Inverse variance MR analyses showed that reduced ‘g’ is associated with genetically determined elevation of VAT, BMI and WHR (all P < 0.001). In contrast, MR did not support a causal role for blood pressure, lipid, or glycemic indices on cognition. Interpretation: We show an independent relationship between adiposity and cognition in a multi-ethnic Asian population. MR analyses suggest that both visceral adiposity and raised BMI are likely to be causally linked to cognition. Our findings have important implications for preservation of cognitive health, including further motivation for action to reverse the rising burden of obesity in the Asia–Pacific region. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Ministry of Health (MOH) Nanyang Technological University National Medical Research Council (NMRC) Published version This work was supported by intramural funding from Nanyang Technological University, Lee Kong Chian School of Medicine, and the National Healthcare Group. J.C. is supported by: the Singapore Ministry of Health and National Medical Research Council STaR funding scheme [NMRC/StaR/0028/2017], LCG funding [MOH-000271], and Phase 2 National Precision Medicine Programme (Research Platform and Data Enablers) [NMRC/PRECISE/2020]; and the Singapore Agency for Science Technology and Research IAF-PP National Precision Medicine Program Phase 1A (A Population Level Genomic Infrastructure) [H17/ 01/a0/007] and IAF-PP Asian Skin Microbiome Programme [H18/01/ a0/016]. T.M. received postdoctoral fellowship from the Singapore Ministry of Education – Research Scholarship Block and Lee Kong Chian School of Medicine.