Reither, Erin, Robert Hauser, and Karen Swallen
Working paper no. 2006-11
Some of the richest longitudinal studies in the social sciences did not, at their outset, gather biomarkers that are routinely recorded today—including the height and weight of participants. The Wisconsin Longitudinal Study (WLS) is a large cohort study of over 10,000 individuals that fits this description. To account for this shortcoming, an eleven point scale was developed to code the senior yearbook photographs of WLS participants for relative body mass (RBM). It is a reliable (α=0.91) and valid way to assess body mass. Despite the passage of 36 years between measures, the standardized relative body mass index (SRBMI) was moderately correlated (r = 0.31) with body mass at index (BMI) at ages 53-54 and uncorrelated with height. Overweight adolescents (defined as at or above the 90th percentile of SRBMI) were about three times more likely than normal weight adolescents (5th to 85th percentile) to be obese in adulthood and, as a likely consequence, significantly more likely to report health problems such as chest pain and diabetes. Sadly, overweight adolescents also suffered twofold risk of premature death from all non-accidental causes and fourfold risk of heart disease mortality. The RBM scale has removed a serious obstacle to obesity research in the WLS, highlighting the promise of innovative new solutions for other longitudinal studies that currently lack measures of body mass.