Background: To assess the association of body mass index with mortality in a population-based setting of older people in Thailand.
Methods: Baseline data from the National Health Examination Survey III (NHES III) conducted in 2004 was linked to death records from vital registration for 2004-2007. Complete information regarding body mass index (BMI) (n = 15997) and mortality data were separately analysed by sex. The Cox Proportional Hazard Model was used to test the association between BMI and all-cause mortality controlling for demographic, socioeconomic, and health risk factors.
Results: During a mean follow-up time of 3.8 years (60545.8 person-years), a total of 1575 older persons, (936 men and 639 women) had died. A U-shaped and reverse J-shaped of association between BMI and all-cause mortality were observed in men and women, respectively. However there was no significant increased risk in the higher BMI categories. Compared to those with BMI 18.5-22.9 kg/m2, the adjusted hazard ratios (HR) of all-cause mortality for those with BMI <18.5, 23.0-24.9, 25.0-27.4, 27.5-29.9, 30.0-34.9, and ≥35.0 were 1.34 (95% CI, 1.14-1.58), 0.79 (95% CI, 0.65-0.97), 0.81 (95% CI, 0.65-1.00), 0.67 (95% CI, 0.48-0.94), 0.60 (95% CI, 0.35-1.03), and 1.87 (95% CI, 0.77-4.56), respectively, for men, and were 1.29 (95% CI,1.04-1.60), 0.70 (95% CI, 0.55-0.90), 0.79 (95% CI, 0.62-1.01), 0.57 (95% CI, 0.41-0.81), 0.58 (95% CI, 0.39-0.87), and 0.78 (95% CI, 0.38-1.59), respectively, for women.
Conclusions: The results of this study support the obesity paradox phenomenon in older Thai people, especially in women. Improvement in quality of mortality data and further investigation to confirm such association are needed in this population.