Effect of choice of outcome measure on studies of the etiology of obesity in children.
OBJECTIVE
Epidemiologic studies of the etiology of childhood obesity often use proxies for adiposity as outcomes. This study aimed to compare the ability of a range of proxy measures to detect associations with sedentary behavior.


METHODS
Longitudinal study of children in the Gateshead Millennium Study who were 7 years at baseline and 9 years at follow-up. Associations between 2-year changes in objectively measured sedentary behavior and changes in proxies for adiposity (waist circumference, waist Z score, body mass index, body mass index Z score) and measurement of body composition (fat mass index from bioelectric impedance) were examined. Associations were tested with linear regression.


RESULTS
Associations between 2-year increases in sedentary behavior and increases in adiposity were detectable by using the fat mass index as the outcome, but not the simple proxy measures of adiposity, as outcomes.


CONCLUSIONS
Proxy measures are inferior to measures of body composition as outcomes in epidemiologic studies.
Institute of Health and Society, Human Nutrition Research Centre, Newcastle University, Newcastle upon Tyne, UK.
Laura
L
Basterfield
Mark S
MS
Pearce
Ashley J
AJ
Adamson
Jessica K
JK
Reilly
Kathryn N
KN
Parkinson
John J
JJ
Reilly
D061725:Accelerometry; D056044:Actigraphy; D050154:Adiposity; D015992:Body Mass Index; D002648:Child; D002755:Choice Behavior; D005260:Female; D006801:Humans; D016014:Linear Models; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D009043:Motor Activity; D009765:Obesity / Q000209:etiology*; D017063:Outcome Assessment, Health Care; D012307:Risk Factors; D057185:Sedentary Behavior; D012959:Socioeconomic Factors; D055105:Waist Circumference