How accurately are height, weight and leg length reported by the elderly, and how closely are they related to measurements recorded in childhood?

Background This paper examines (1) the accuracy of self-reported height, le g length and weight in a group of subjects aged 56-78; (2) whether recent m easurement of height and weight influences the accuracy of self-reporting a nd (3) associations between childhood and adult height, leg length and BMI measured in old age. Methods All 3182 surviving members of the Boyd Orr cohort were sent postal questionnaires in 1997-1998 and a sub-sample (294) was also clinically exam ined. Results Self-reported height was overestimated and body mass index (BMI), b ased on reported height and weight, underestimated. The mean difference bet ween self-report and measured values were for height: 2.1 cm in males and 1 .7 cm in females; for BMI the difference was -1.3 kg/m(2) in males and -1.2 kg/m(2) in females. Shorter individuals and older subjects tended to over- report their height more than others. The overweight under-reported their w eight to a greater extent. Recent measurement appeared to decease over-repo rting of height but not weight. Correlations between self-report and measur ed height and BMI were generally over 0.90, but weaker for leg length (r = 0.70 in males and 0.71 in females). Adult height and leg length were quite closely related to their relative values in childhood (correlation coeffici ents ranged from 0.66 to 0.84), but associations between adult and childhoo d BMI were weak (r = 0.19 in males and 0.21 in females). Conclusions Self-reported measures of height and weight may be used in stud ies of the elderly although systematic reporting errors may bias effect est imates, As overweight individuals tend to under-report and the short and un derweight tend to over-report, studies investigating associations of diseas e with height and weight using self-reported measures will underestimate ef fects. The weak associations between childhood and adult BMI indicate that associations between childhood adiposity and adult cardiovascular disease f ound in this cohort may reflect the specific effect of childhood overweight , rather than its persistence into adulthood. This suggests that avoidance of adiposity may be as important in childhood as in adulthood.