Cross-sectional and longitudinal analyses of variations of anthropometric measures of obesity with age in the Jackson Heart Study

OBJECTIVE: To explore how anthropometric measures of obesity vary with age among African American (AA) adults. PARTICIPANTS AND SETTING: 3634 AA adults participated in the Jackson Heart Study (Jackson, Mississippi, USA) from 2004 to 2013. OUTCOME MEASURES: Body mass index (BMI), waist circumference (WC), waist-to-height ratio (WHtR) and waist-to-hip ratio (WHR). METHODS: Linear regression models were used to estimate the mean differences in anthropometric measures cross-sectionally by age group. Longitudinal changes in anthropometric measures over time (ie, the ageing effect) within each sex and age group were analysed using mixed effects models. All regression models were adjusted for education and lifestyle factors. RESULTS: In cross-sectional analysis, older age was associated with lower BMI, WC and WHtR, but higher WHR in both sexes. Compared with 25 to <44 years age group, the mean (95% CI) BMI, WC and WHtR was 0.80 (0.66 to 0.94), 0.27 (0.13 to 0.42) and 0.18 (0.03 to 0.32) standardised (SD) unit lower, while WHR was 0.48 (0.33 to 0.62) SD unit higher in the 75+ years age group. In longitudinal analysis, ageing was associated with increased BMI, WC and WHtR, among younger age groups but not in older age groups. However, WHR tended to increase with ageing across all age groups in both sexes. Among men 75+ years old, the mean change (95% CI) in BMI, WC and WHtR for every 5 years increase in age, was –0.20 (–0.29 to –0.11), –0.19 (−0.31 to –0.07), –0.15 (−0.27 to –0.02) SD unit, respectively, while it was 0.24 (0.05 to 0.44) SD unit for WHR. CONCLUSIONS: Among middle-aged AA adults, all four anthropometric measures of obesity examined increased with ageing. However, among elderly AA adults, only WHR showed continued increase with ageing. WHR may be a better anthropometric measure for monitoring obesity in older AA adults.