Social and environmental factors and life expectancy, infant mortality, and maternal mortality rates: results of a cross-national comparison.

Using data from United Nations sources we conducted an international comparison study of infant and maternal mortality rates and life expectancy at birth. We examined these three dependent variables in relation to a range of independent variables including dietary factors, medical resource availability, gross national product (GNP/capita), literacy rates, growth in the labor force, and provision of sanitation facilities and safe water. Based on exploratory stepwise regression models, we fitted a series of general linear models for each of the three dependent variables. For the models with the highest explanatory ability, the percent of households without sanitation facilities showed the strongest association with all three dependent variables: life expectancy at birth (R2 = 0.83, B = -0.088, P = 0.0007); infant mortality rate (R2 = 0.87, B = +0.611, P < 0.0001); and maternal mortality rate (R2 = 0.54, B = +8.297, P = 0.002). Additional significant predictors of life expectancy at birth and infant mortality rate included the quantity of animal products consumed, the percent of households without safe water, excess calories consumed as fat, and the total literacy level. Maternal mortality rate was significantly associated with total energy consumption and excess energy consumed as fat. Using residuals from the general linear models we chose three outlying countries: Costa Rica, Sri Lanka and Egypt, on which to do case studies. These country case studies are discussed briefly in regard to characteristics that could account for their differing statistical relationships.