Relationship between LBW infant rate by prefecture and biological socio-economic factors in Japan: an ecological study
In Japan, the low birth weight (LBW) rate has been increasing in recent years. LBW infants are at increased risk for a number of diseases later in life, but the risk factors is not clear.
METHODS:
We therefore conducted a systematic review of the factors associated with a higher incidence of LBW and selected 28 biological socio-economic factors. We used 44 indexes that linked to 28 biological socio-economic factors from “Population Survey Report 2009” as an objective variable. In addition, “number of infants under 2500 g (LBW infants) rate by prefecture” was used as an explanatory variable.
Two analyses were conducted in this study. We first performed a multiple correlation analysis between 28 biological socioeconomic factors and LBW rate, and then conducted a multiple regression analysis using the factors that were significantly correlated with LBW.
RESULTS:
The results were as follows. The Gini coefficient (β = 0.458, p < 0.001) that we obtained was R² = 0.192. However, since the effect of the Gini coefficient was so large, we conducted another multiple regression analysis excluding the Gini coefficient from the independent variable. The result of the reanalysis was R² = 0.245, and the factors used were birth rate of 40–44-year-old mothers (β = 0.535, p < 0.001), rate of college/graduate school graduates (β = -0.670, p = 0.004), and women’s average sleeping time (β = -0.463, p = 0.034).
CONCLUSIONS:
The present findings suggest that regional differences in LBW rate are due to economic differentiation. It was expected that the mother’s household income or educational background would correlate with LBW rate, but we could not make it clear in this study. The possible reason for this is because our subject in this research/study was each prefecture, which is relatively large. Future studies should examine the factors affecting LBW rate in municipalities