Community-based analysis of the factorial structures of the recent increase in low birthweight infants.

This study was conducted to determine whether the regional factors were related to the increase in the percentage of low birthweight (LBW: <2,500g) infants in Kumamoto Pref., and to establish a tentative structure model for predicting low birthweight infants. Analyses for frequency of LBW infants between 1974 and 1997, and a multiple regression model and covariance structure model were conducted using data from the vital statistics between 1992 and 1997 and regional indicators concerned with LBW infants from official registered statistical data between 1992 and 1997. The 72 regional factors were clustered into four groups linked with agricultural areas such as Urban, Flat, Hilly and Mountainous areas. The recent increase in the incidence of LBW infants resulted from the increase in moderate-LBW (MLBW: 2,000-2,500 g) infants of full term-LBW infants. There was a steady annual increase in the Urban agricultural area LBW infants since 1992. The two structure analyses revealed that the Urban area had a marked effect on the increase in LBW infants, whereas, farm villages in Hilly or Moutainous areas had less effect on the increase in LBW infants. These findings suggest that the regional factors relating to the mothers' life-style or regional environments play a key role in the etiology and prevention of LBW, and will be a useful in the analyses using official registered material.