Breast-feeding provides nutritional, immunological and developmental benefits for human infants. In the present 2-year follow-up study, EBF among children born to HIV-infected women was strongly associated with reductions in risk of cough, cough and fever, cough and difficulty breathing or chest retraction or refusal to feed, acute diarrhoea, watery diarrhoea, dysentery, fever and outpatient visit during the first 6 months of life. The observed beneficial effect of EBF for cough continued in the first 12 months of life. The importance of these findings lies in the demonstration of health benefits of EBF, especially reduction in respiratory and diarrhoea morbidity among children born to HIV-infected women. These results are similar to those reported from other studies that examined the associations of EBF and child morbidity outcomes(12,31,32)
; however, the previous studies were done in different settings and populations. In a cohort study from India, the risk of diarrhoea among 6–11-month-old infants was threefold higher among those who had PBF at or below 3 months compared with infants who had EBF beyond 3 months(31)
. In another longitudinal study in Peru, the prevalence of diarrhoea among children who were partially breast-fed was double that among children who were exclusively breast-fed (15 % v
. 7 %) during the first 6 months of life(12)
. In that study children who were par tially breast-fed at 3–5 months had a threefold higher risk of diarrhoea using the prevalence data and had 1·8-fold insignificant risk of diarrhoea using the incidence data compared with children who were exclusively breast-fed. In the Philippines, the risk of diarrhoea comparing partially breast-fed children at 4 months with those who were exclusively breast-fed beyond 4 months was found to be 12·9 in the urban and 6·3 in the rural sample(32)
The advantages of EBF include provision of nutrients and reduced exposure to pathogens in contaminated complementary foods, thereby decreasing the risk of gastrointestinal infections(33)
. Potential mechanisms whereby EBF would reduce the risk of infectious diarrhoea are through provision of immune factors in the gut that may inhibit pathogens and by enhancing the integrity of infant gut mucosa. The presence of immune factors and adequate nutrients in breast milk could also enhance infant systemic immune function and nutritional status, thus lowering the risk of infectious morbidity such as respiratory illnesses. Secretory IgA (sIgA) antibodies for instance are the main component of humoral factors(8)
, and protect against viral(34,35)
and bacterial infections(35–37)
. Non-specific factors such as lactoferrin, lysozymes, nucleotides, oligosaccharides and cytokines in breast milk further aid the sIgA functions(2)
. Breast milk has growth factors that enhance infant gastrointestinal maturity and function and help maintain gut mucosa integrity.
Inconsistent results on the relationship between EBF and child growth have been reported in a few studies. No difference in weight gain and length gain at 4–6 months was found among children fully breast-fed (defined as no other nutritive foods or liquids) compared with partially breast-fed infants in the Philippines(38)
. Also a study in Sudan that compared EBF and PBF showed no significant difference in weight gain, but higher length gain in the EBF group during 20–24 weeks of age(39)
. In a cohort study from Belarus, EBF for 3 months was associated with significantly greater weight and length gain during 3 to 6 months compared with children exclusively breast-fed for 6 months or more(9)
. Findings from Brazil showed that EBF was associated with reduced diarrhoea episodes and better WAZ overall(40)
. Our study did not find any benefit or disadvantage in exclusive v
. partial breast-feeding in relation to growth faltering.
The major strength of our study is the prospective nature in which data were collected, allowing for a proper temporal relationship to be assessed between EBF and infectious and other morbidities. However, the study had several limitations. It is possible that methodological limitations may have accounted for the lack of association between EBF and growth faltering, for instance, since much of the morbidity data were based on 1-month recalls by mothers and it is possible that mild symptoms such as cough and diarrhoea may not have been recalled well for that long, which may have led to misclassification of these endpoints. On the other hand, such misclassification is most likely non-differential with respect to EBF status and might have led to null associations. We also conducted analysis combining both HIV-infected and non-infected children primarily because there were only a few HIV-infected children during the first 2 years of follow up. Furthermore, the results of the present study may not be generalizable to children born to mothers with a later HIV disease stage since only 20 % of the mothers in our study were stage II or higher at enrolment.
In conclusion, we observed a strong association between EBF and significant reduction in the risks of respiratory and diarrhoeal morbidities during the first 6 months of life among children born to early-stage HIV-infected women in Tanzania. These findings support the recommendation of promoting EBF from 4 to 6 months among HIV-infected women who opt to breast-feed. Therefore, women should be supported in their choice of infant feeding practices and educated on the advantages and disadvantages of exclusive v. partial breast-feeding.