The trend of BMI values of US adults by deciles, birth cohorts 1882–1986 stratified by gender and ethnicity

Abstrakt

We estimate trends in BMI values by deciles of the US adult population by birth cohorts 1882-1986 stratified by ethnicity and gender. The estimates are based on a flexible Box-Cox-t (BCT) family and the semiparametric GAMLSS approach, Rigby and Stasinopoulos (2006). The estimates show that the BMI distribution became increasingly right skewed over the years covered by our model. The rate of change of the BMI decile curves varied greatly over time and across gender and ethnicity. The BMI deciles of white men and women experienced upswings after the two world wars and downswings during the Great Depression and also decelerated after 1970. However, among African Americans the pattern is different during the first half of the century with men's rate of increase in BMI values decreasing substantially and that of females remaining constant at a relatively high level until the Second World War. After the war, though, the rate of change of BMI values of blacks came to resemble that of whites.