Interpreting the Evidence of Body Mass Index in Relation to Mental Health Status in Community-Dwelling Older Adults

Introduction: Maintaining a better physical and mental health status is an important issue for older adults in their later life. Thus, the study's purpose was to evaluate the association between body mass index (BMI) and mental health status in older adults aged 65 years old or above residing in communities of Taipei City, Taiwan. Methods: We carried out secondary data analysis with data from a volunteer-based health examination project for older adults >65 years old residing in Taipei City from 2006 to 2010 with a retrospective study design. BMI, calculated by standardized measuring procedures for height and weight, and mental health status, evaluated by 5-item Brief Symptom Rating Scale (BSRS-5), were collected at their first visits of health examination. A BSRS-5 score >= 6 was considered an inferior mental health status for the outcome. In statistical analysis, univariable and multivariable logistic regressions were adopted to estimate the relative risk of inferior mental health status, treating BMI as the major exposure of interest. Results: A total of 90,576 subjects were involved, with a mean age of 73.38 years old (SD = 6.64 years) and 49.21% females. With confounders controlled, compared to normal or overweight (23 <= BMI <30), an adjusted OR of 1.23 (95% CI: 1.18, 1.29) on inferior mental health status was detected for the underweight group (BMI <23) significantly. Adjusted OR for those obese (BMI >= 30) was 0.87 (95% CI: 0.79, 0.96). Significantly elevated ORs of underweight were found for both genders, but the significantly protective effect of obese was only detected for females. Conclusion: Keeping an appropriate weight or even being overweighted might be beneficial for older adults dwelling in the community, especially for males.