ARTICLE ANALYSIS

Article Analysis



Article Analysis

Introduction

The article under review is “What are the causal effects of breastfeeding on IQ, obesity and blood pressure? Evidence from comparing high-income with middle-income cohorts” by Marie-Jo A Brion, Debbie A Lawlor, Alicia Matijasevich, Bernardo Horta, Luciana Anselmi, Cora L Araújo, Ana Maria B Menezes, Cesar G Victora, and George Davey Smith, published in International Journal of Epidemiology in 2011.

How to breastfeed and express breastmilk involve many preferences of the mother and baby. There are several recommended positions (such as the cradle or football hold); schedules (alternating breasts during a feeding or one breast for a feeding, or alternating each time); and length of breastfeeding episodes (for example, 20 minutes or as long as the baby wants). Further, expressing breastmilk can be performed by baby-only, the hand, handheld manual pump, electric handheld pump, or institutional-grade electric pump. Among the many possible preferences, time and comfort may be the most common criteria among women.

Most studies of the effects of breastfeeding on overweight and obesity involve samples of children. Four studies examine an older group, one a UK cross-sectional study of children aged 9-18 years and the same data set at 33 years of age. Another study from New Zealand examined longitudinal data of 1037 children aged from birth to 26 years. All found the possibility of an effect of breastfeeding which disappeared when confounding variables were taken into account and all used body mass index (BMI) only as an outcome. One study using the Nurses' Health Study II in the USA examined subjects at five, 10, 18 years and current age at time of questionnaire completion in 1989 and found no effect on obesity at 18 years or later of breastfeeding. However, data for this study were dependent on subjects' recall in 1989 and their mothers' recall of breastfeeding.

There is much interest in the topic of the effects of breastfeeding on weight, with many finding that the link is tenuous. Three meta-analyses were inconclusive. One used 31 studies, another included 17, while a third included nine. Of those, nine papers were common to all. Harder et al. (2005) found that a pooling of results of 17 published studies strongly supported a dose-dependent influence of duration of breastfeeding and a decrease in the risk of overweight at various ages. Arenz et al. (2004), using the same studies, found a small but effective protective effect of breastfeeding. Owen et al. (2005) with 31 studies, found that mean BMI was lower among those who were breastfed, but these differences were only small and subject to confounding. A critical review and meta-analysis described a negative association between breastfeeding and later obesity in the observational studies included, but questioned the ability to draw sound conclusions from the level of evidence, as, for ethical reasons, it is not possible to conduct a randomised, controlled trial on this.

Employers can reap benefits, such as decreased absenteeism and increased productivity, if they invest in supporting lactation for their employees. Breastfeeding has also been associated with a reduction in health care ...