Are inequalities in height underestimated by adult social position? Effects of changing social structure and height selection in a cohort study.

OBJECTIVES To investigate whether changing social structure and social mobility related to height generate (inflate) inequalities in height. DESIGN Longitudinal 1958 British birth cohort study. SETTING England, Scotland, and Wales. PARTICIPANTS 10 176 people born 3-9 March 1958 for whom data were available at age 33 years. MAIN OUTCOME MEASURES Adult height and social class at age 33 years; class of origin (father's occupation when participant was 7 years old). RESULTS Adult height showed a social gradient with class at age 7 years and age 33 years. The difference in mean height between extreme groups was greater for class of origin than for adult class, reducing from 2.21 cm to 1.62 cm for men and from 2.18 cm to 1.74 cm for women. This narrowing inequality was due mainly to a decrease in mean height in classes I and II. This was because of the pattern of height related social mobility in which, for example, men moving into classes I and II were taller (mean 177.2 cm) than men remaining in class III manual (mean 176.1 cm) yet shorter than men with class I and II origins (mean 178.3 cm) and the relatively large number of individuals moving into classes I and II. Changes in the structure of society, seen here with the general trend of upward social mobility, have acted to diminish inequalities in adult height. CONCLUSIONS The combination of changing social structure and height related mobility constrains, rather than inflates, inequalities in height and may lead to an underestimation of the role of childhood socioeconomic factors in the development of inequalities in adult disease.