br It s that time of year again when we
It\'s that time of year again when we ask readers to submit photographs for our annual Highlights photography competition. We are looking for striking images that arrest our attention about any topic in medicine, from global health to clinical medicine, from the individual person to populations. An image can be a powerful way to tell a story. As we have seen with past Highlights winners, your photographs about the health stories that speak to you capture important moments in clinical and global health. Last year\'s beautiful selection of winning photographs included images about neonatal care in Africa, the work of midwives in Afghanistan, the life of sex workers in India, and the importance of purchase NVP-TNKS656 health workers in bringing health care to homes. We are interested in photographs from any country and invite readers to submit photographs to Highlights 2015 that capture any health issue in a thought-provoking way. As in previous years, and will run the competition together. Winning photographs will be published in \'s final issue of 2015 and might also be selected for the front cover of .
Cesar Victora and colleagues (April, 2015) report that breastfeeding is associated with children developing higher intelligence quotients (IQ) in later life. Victora and colleagues viewed this association as being causal. However, their experimental design ignored two important facts: first, that the children were biologically related to their mothers; and second, that adult IQ is strongly heritable (narrow heritability of at least 0·5, meaning that additive genetic effects account for half the variation in intelligence from person to person in Western populations). These genetic effects also interact with socioeconomic status. Mothers with high IQs might be more likely to breastfeed their children than mothers with lower IQs. The increased IQ of their children would then be a consequence of simple genetic transmission. Breastfeeding might have little direct effect on the IQ of the offspring. Evidence suggests that this is the case. Mothers with higher IQs are far more likely to breastfeed than are mothers with lower IQs; one SD difference in IQ more than doubled the odds of a mother breastfeeding. Furthermore, controlling for maternal IQ halved or—with the inclusion of socioeconomic status—eliminated any association between breastfeeding and adult IQ compared with bottle feeding. These studies also showed that maternal education is not an effective proxy for maternal IQ. Thus, although Victora and colleagues controlled for maternal education, this probably did not adequately control for maternal IQ.
Cesar Victora and colleagues used a large Brazilian sample to investigate the effect of breastfeeding on children\'s intelligence quotient (IQ), education, and earnings at age 30 years. They noted that, after adjustment for confounders, infants who were breastfed for 12 months or longer had, on average, about 4 points higher IQs, about 1 year more of schooling, and a monthly income that was roughly 350 Brazilian reals higher than did children who were breastfed for less than 1 month. Importantly, they identified a dose-response effect for breastfeeding—with almost every increase in the duration of breastfeeding, there was a slight rise in IQ.
Cesar Victora and colleagues use a robust method to show an association between the duration of breastfeeding and adult intelligence, educational attainment, and professional success. However, some potentially important confounders are overlooked. These confounders include the birth interval between children and family size. It is well established that breastfeeding increases the interval between siblings. Direct evidence from the UK National Child Development Study, which included 17 419 participants, showed that increasing birth interval was associated with increasing childhood intelligence as measured by intelligence quotient (IQ). This association was independent of birth order, number of siblings, social class, and maternal or paternal education level. Indeed, the older the children the more demonstrable the effect. Hence, increasing birth interval had a much stronger positive effect on intelligence at age 16 years than in early childhood. This lends support to the notion that molecular biology is the effect of birth interval not lactation per se that affects adult outcomes. Wagner and colleagues in their early review in 1985 also found short sibling spacing to have a deleterious effect on intelligence.