title: Defects of the central nervous system in Finland: I. Variations in time and space, sex distribution, and parental age.
abstract: Data from the Finnish Register of Congenital Malformations for the years 1965-73 were used in a search for associations between environmental influences and defects of the central nervous system (CNS). The material consisted of 710 cases of CNS defects and their matched-pair controls. Moreover, and 'internal' control group of 259 cases of polydactyly and their matched-pair controls were used. The first report gives information on variations in time and space, sex distribution, and parental age. A higher incidence of anencephaly was noted in the eastern part of the country, but no significant secular or seasonal variations were found. The sex ratio (M/F) was lower than expected in the groups of anencephaly and CNS defects as a whole. High parental age turned out to be a risk factor in the group of all CNS defects, mainly owing to the subgroup of hydrocephaly. The dangers of observational studies due to confounding factors are discussed.
mesh_terms: D000328:Adult; D000367:Age Factors; D000757:Anencephaly / Q000453:epidemiology; D002490:Central Nervous System / Q000002:abnormalities*; D002648:Child; D004777:Environment; D005260:Female; D005387:Finland; D006801:Humans; D006849:Hydrocephalus / Q000453:epidemiology; D008297:Male; D010507:Periodicity; D012621:Seasons; D012737:Sex Factors; D016136:Spina Bifida Occulta / Q000453:epidemiology