Editor,— Differences in mortality between areas have been found to be related to the socioeconomic conditions of the area.1 2 However, people also move to improve their physical and social environment, and the health status of the migrants differs considerably from that of the non-migrants.3Recently, Davey Smith and collegues4 found that mortality, measured 1991–92, was inversely related to the population growth in the two preceding decades in 292 areas in Britain. They found a negative correlation between population change and mortality both in men and women, although the correlation was somewhat stronger in men.

We investigated the association between population growth and mortality in the 16 municipalities of the county of Värmland in Sweden. The population change, as percentage increases or decreases between 1975 and 1994 was counted from the official population statistics. In Sweden, the official population statistics are based on continuous registration of births, deaths and migration. Although the population change was similar in both sexes (correlation 0.99), we calculated it separately for men and women. Mortality in 1992–96 was derived from the database administered …