Association of body mass index with Short-Form 36 physical and mental component summary scores in a multiethnic Asian population

Abstract

To investigate the association between body mass index (BMI) and physical and mental health-related quality of life (HRQoL) in a multiethnic Asian population in Singapore, and explore whether there were gender and ethnic differences in this association. We conducted cross-sectional analyses using data from 5027 Chinese, Malay and Indian participants (2403 men and 2624 women) aged 24-95 years. These subjects were from four previous cross-sectional surveys carried out in Singapore (from 1982 to 1998) who attended a follow-up examination (including both a questionnaire and a clinic examination) between 2004 and 2007, during which HRQoL was assessed. Participants were classified as underweight (<18.5 kg m(-2)), normal weight (18.5 to <23 kg m(-2)), overweight (23 to <25 kg m(-2)), moderate obese (25 to <30 kg m(-2)) and severe obese (>or=30 kg m(-2)). HRQoL was measured using the Short-Form 36-item questionnaire (SF-36) physical component summary score (PCS) and mental component summary score (MCS). Linear regressions with and without adjusting for other covariates were used to evaluate the association between BMI and SF-36 PCS and MCS. Compared with participants with normal weight, moderate or severe obesity was associated with 0.8 points (95% confidence interval (CI): -1.5 to -0.1, P=0.03) and 2.1 points lower PCS (95% CI: -3.1 to -0.1, P<0.001), respectively, after adjustment for sociodemographic variables, family functioning measure scores and the presence of chronic diseases. These associations were greater in women than in men. In contrast, being underweight was associated with 1.3 points lower MCS (95% CI: -2.3 to -0.3, P=0.014). In this study (one of few studies in the Asia-Pacific region), obesity was associated with lower PCS and the effect was modified by gender but not ethnicity, such that the association was greater in women than in men. However, obesity was not associated with MCS. Underweight was associated with reduced MCS but not PCS.