1Postgraduate Program in Epidemiology, Federal University of Pelotas, Pelotas, Brazil 2International Health and Medical Education Center, University College London, London, UK 3Epidemiology Resource Center, University of Southampton, Southampton, UK 4Postgraduate Program in Health and Behavior, Catholic University of Pelotas, Pelotas, Brazil Correspondence to Dr Ana MB Menezes, Rua Marechal Deodoro 1160, 96020-220, Pelotas, RS, Brazil; anamene@terra.com.br Accepted 19 January 2011 Published Online First 15 February 2011 This paper is freely available online under the BMJ Journals unlocked scheme, see http:// jech.bmj.com/site/about/ unlocked.xhtml Maternal, child and adolescent health Adolescent blood pressure, body mass index and skin folds: sorting out the effects of early weight and length gains Ana M B Menezes,1 Pedro C Hallal,1 Samuel C Dumith,1 Alicia M Matijasevich,1 Cora L P Ara´ujo,1 John Yudkin,2 Clive Osmond,3 Fernando C Barros,4 Cesar G Victora1 ABSTRACT Background Although there is longstanding evidence of the short-term beneﬁts of promoting rapid growth for young children in low-income settings, more recent studies suggest that early weight gain can also increase the risk of chronic diseases in adults. This paper attempts to separate the effects of early life weight and length/height gains on blood pressure, body mass index (BMI), sum of skin folds and subscapular/triceps skin fold ratio at 14e15 years of age. Methods The sample comprised 833 members of a prospective population-based birth cohort from Brazil. Conditional size (weight or height) analyses were used to express the difference between observed size at a given age and expected size based on a regression, including all previous measures of the same anthropometric index. A positive conditional weight or height indicates growing faster than expected given prior size. Results Conditional weights at all age ranges were positively associated with most outcomes; each z-score of conditional weight at 4 years was associated with an increase of 6.1 mm in the sum of skin folds (95% CI 4.5 to 7.6) in adolescence after adjustment for conditional length/height. Associations of the outcomes with conditional length/height were mostly negative or non- signiﬁcantdeach z-score was associated with a reduction of 2.4 mm (95% CI 3.8 to 1.1) in the sum of skin folds after adjustment for conditional weight. No associations were found with the skin fold ratio. Conclusion The promotion of rapid length/height gain without excessive weight gain seems to be beneﬁcial for long-term outcomes, but this requires conﬁrmation from other studies. INTRODUCTION A wide body of evidence supports the short term beneﬁts of promoting rapid weight gain for young children in low-income settings.1e3 However, recently, several authors suggest that early weight gain can also increase the risk of chronic diseases in adults.4e6 Another in this debate is that rapid weight gain in poor populations is positively asso- ciated with human capital in adultsdincluding schooling, economic productivity and next-genera- tion birth weight.7 8 This has been described as the ‘catch-up dilemma’.9 The ﬁrst studies on the long-term consequences of early life exposures suggested that birth weight was inversely associated with the risk of chronic diseases in adulthood,10 but it has been argued that such effect was primarily due to postnatal instead of prenatal weight trajectories.11 Further studies tried to establish whether there was a speciﬁc age range in which rapid weight gain was most strongly associated with beneﬁcial7 8 or detrimental adult outcomes.12 13 Because weight gain in a given age range is not independent from previous weight gains,14e16 conditional analyses have been more recently proposed to overcome the lack of independence.14 Conditional size is deﬁned as the amount by which the size at the end of a time interval exceeds that which would have been predicted at the beginning of the interval from previous measurements of the same anthropometric parameterdfor example, weight or height. A positive conditional weight or height indicates growing faster than expected given prior size. An additional issue yet to be addressed is how to disentangle the long-term effects of early weight gain from those of length/height gain during the same age range during childhood. We have used this novel approach to analyse data from a birth cohort study in Southern Brazil in order to explore the independent effects of weight and length/height gains during different periods in the ﬁrst 4 years of life on blood pressure and on measures of obesity and central fat distribution at 14e15 years of age. METHODS Pelotas is a 340 000-inhabitant city located in the extreme south of Brazil near the border with Uruguay and Argentina. All hospital-born children in 1993 whose families were residents of the city (N¼5265) were eligible for a birth cohort study; there were only 16 refusals.17 18 Low birth weight (<2500 g) children comprised 9.8% of the sample. All low birth weight children and a random 20% sample of the remaining children (N¼1454) were followed up at home at the ages of 6, 12 and 48 months, and all cohort participants were visited at the age of 14e15 years. Analyses presented here are restricted to subjects located in these four waves of data collection and are weighted to represent the total population. Further details on the methodology of the 1993 Pelotas (Brazil) birth cohort study are available elsewhere.17 18 Birth weight was measured at the hospital by the study team using paediatric scales (Filizola, Sao Paulo, Brazil) with a precision of 10 g, and birth length with a locally made infantometer with J Epidemiol Community Health 2012;66:149e154. doi:10.1136/jech.2010.124842 149