Body Shape Index: Sex-specific Differences in Predictive Power for All-cause Mortality in the Japanese Population

Background: While body mass index (BMI) is the most widely used anthropometric measure, its association with all-cause mortality is generally J-shaped or U-shaped. A body shape index (ABSI) is a recently formulated anthropometric measure that shows linear relationship to all-cause mortality, especially in Caucasian cohorts. We aimed to address the relationship between ABSI and all-cause mortality in Asians and to assess the influence of sex difference and of chronic kidney disease (CKD) on this relationship.

Methods: This was a longitudinal cohort study assessing the association of ABSI, BMI, waist circumference (WC), and waist-to-height ratio (WHtR) with all-cause mortality in a Japanese nationwide Specific Health Checkup database. The study enrolled 160,625 participants followed-up between 2008 and 2012. We calculated the all-cause mortality risk associated with a 1-standard deviation increase (+1SD) in ABSI, BMI, WC, or WHtR in cohorts stratified by sex and the presence of CKD.

Results: During the 4-year follow up, 1.3% of participants died. In men, ABSI (+1SD) significantly increased the risk for all-cause mortality after adjusting for other known risk factors including CKD; hazard ratio (HR) and 95% confidence intervals (CI) of non-CKD cohort, 1.30 (1.18 to 1.43), p<0.01; HR and 95%CI of CKD cohort, 1.16 (1.01 to 1.34), p = 0.04. In women, ABSI (+1SD) did not show significant association with all-cause mortality, especially in the CKD cohort; HR and 95% CI of non-CKD cohort, 1.07 (0.99 to 1.17), p = 0.09; HR and 95%CI of CKD cohort, 0.98 (0.84 to 1.14), p = 0.78. Conversely, BMI (+1SD) was associated with significantly lower risk in men, although minimal association was found in women. WC and WHtR showed little association with all-cause mortality. On stratification per ABSI quartiles, mortality risk increased linearly and significantly with ABSI in men, but not in women with CKD. Both BMI and WC showed significant but U-shaped association with mortality in the non-CKD cohort and in men with CKD. WHtR also showed significant U-shaped association with mortality in men.

Conclusions: In the Japanese population, ABSI showed significant and linear correlation with mortality risk in men but not in women, especially in the presence of CKD.