First-borns have a higher metabolic rate and carry a higher metabolic risk in young women attending a weight loss clinic

Abstract

First-born status is associated with significantly elevated metabolic risk in a clinical population of overweight and obese young women attending a weight loss clinic. If these findings are confirmed in other studies, they may suggest that the prevalence of the metabolic syndrome worldwide may increase as a function of the trend to smaller family size.

First-borns have greater BMI and are more likely to be overweight or obese: a study of sibling pairs among 26 812 Swedish women

“…There seem to be very little data on the association between birth order and height in women, and none from large studies. Previously, the study on Italian women observed no difference in stature between first-borns and later-borns,10 while among Indian women, there was a weak correlation between birth order and stature (r=−0.20), but the magnitude of the effect was not quantified 11. In contrast, data from large studies have consistently reported differences in men.…”

“…These observed associations between birth order and female adiposity corroborate data from previous studies on women who were not sibling pairs. In Italy, among 383 overweight or obese women, first-borns had more body fat and had BMI that was 4 kg/m 2 greater than later-borns 10. Similarly, a study on 171 young adult women in India showed that birth order was negatively correlated with BMI and fat mass 11.…”

“…The New Zealand study on overweight middle-aged men also observed that first-borns had lower insulin sensitivity than second-borns,13 noting that insulin sensitivity is an independent predictor of metabolic and cardiovascular diseases 16. Only the Italian study appears to have specifically examined health outcomes in adult women, observing that first-borns had an elevated metabolic risk compared to later-borns 10. However, the study was carried out on a highly selected group (overweight and obese young women attending a weight loss clinic) who were not sibling pairs, so that their findings cannot be readily extrapolated to the general adult female population.…”

The association of birth order with later body mass index and blood pressure: a comparison between prospective cohort studies from the United Kingdom and Brazil

“…Maternal schooling at the time of delivery for mothers of the Pelotas 2004 cohort was collected as a continuous variable and categorised according to the Brazilian Education System. The System is divided into three levels: fundamental (grades 1–8), intermediate 9, 10, 11 and higher education (⩾12 years of formal education). Because of few numbers of women without any formal education (0 years) and with higher education, we opted to join these women with the nearest category available.…”

“…Most of the evidence supporting the hypothesis that first born children are at greater cardiovascular risk has come from low- and middle-income countries; studies in higher income countries have had more mixed findings. 9, 10, 11, 12, 13, 14 …”