Environmental factors in the relationship between breastfeeding and infant mortality: the role of sanitation and water in Malaysia.

Mothers' recall data collected in Malaysia in 1976-1977 are analyzed to study correlates of mortality of 5471 infants. Respondent population is 1262 women living in 52 primary sampling units of Peninsular Malaysia. Lengths of unsupplemented and supplemented breastfeeding and presence of piped household water and toilet sanitation are related to infant mortality in regressions that also control other correlates. The analysis is disaggregated into three periods of infancy. Through six months of feeding, unsupplemented breastfeeding is more strongly associated with fewer infant deaths than is supplemented breastfeeding. Type of sanitation is generally more strongly associated with mortality than is type of water supply. The effects of breastfeeding and the environmental variables are shown to be strongly interactive and to change systematically during the course of infancy. Breastfeeding is more strongly associated with infant survival in homes without piped water or toilet sanitation. In homes with both modern facilities, supplemented breastfeeding has no significant effect, and unsupplemented breastfeeding is statistically significant only for mortality in days 8-28. Presence of modern water and sanitation systems appears unimportant for mortality of infants who are breastfed without supplementation for six months.