Comparison between research data and routinely collected register data forstudying childhood health

Cohort studies are usually based on detailed information gathered on a limi ted number of individuals. Increasing collection of administrative register s offers an alternative method to gather health data. In the first study he alth information from birth until the age of seven years on 8708 children b orn in the two most northern provinces of Finland in 1985-86 was gathered t hrough questionnaires, medical record reviews, medical examinations and som e register data. In the second study, similar information on 8222 children born in the same provinces in 1987 was gathered using administrative regist ers. Both data collection methods gave equal results for mortality, long-te rm medication, and cumulative incidence of diabetes and intellectual disabi lities. The register data identified more children with delayed development , but less children with long-term illness (77% of the level identified by the research data), with asthma (74%), and with epilepsy (40%). The registe r data was unsuitable for investigating hearing and vision disorders. The a dministrative data gave a gender ratio similar to that of the research data for two of the variables with poor coverage (asthma and epilepsy), but ide ntified more boys with long-term illness in general than the research data. Administrative registers are useful for studying many long-term health pro blems, e.g. those resulting in hospital care or social benefits or those re gistered in vital statistics. Specific cohort studies with separate data co llection is still needed to study for example outpatient care, self-assesse d health, growth and development.