Towards an equal distribution of health? Socioeconomic and regional differences of the secular trend of the age of menarche in Finland from 1979 to 1989.

The purpose of this study was to investigate if a secular trend towards an earlier age of menarche still existed in Finland in the 1980s and if social class and regional differences observed previously in the mean age of menarche had disappeared. Questionnaires were mailed to nationwide representative samples of 16- and 18-year-old girls every other year from 1979 to 1989. At the national level, the secular trend towards an earlier menarche was not observed in the 1980s but the trend was significant among girls living in the North-West and rural areas. Clearly observed regional and urban-rural differences in 1979 disappeared in the 1980s. Social class differences persisted: farmers' daughters had a higher mean age of menarche than those of other occupational groups. Adolescents in the 1980s displayed a more even distribution of health than the cohorts born before them. Improved welfare of the Finnish society and reorganization of the primary health care are probable explanations.