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Progressive encephalopathies in the west Swedish region were investigated in a population-based study. Cases were allocated to one of five main groups: 1) disorders covered by impairments in subcellular organelles, 2) disorders covered by deficiencies in the intermediate metabolism, 3) biochemically undefined neurometabolic disorders, 4) neuroimmunological disorders and 5) a symptom-orientated miscellaneous group. Progressive encephalopathies were identified in 76 of 132,138 children born alive in the study area during the 16-year-period 1970-85. This gives a live birth prevalence of 0.58 per 1000. In Sweden the size of the group corresponds to that of neural tube defects and that of congenital hydrocephalus. However, a vast number of different disorders are represented.

In recent years research on senile dementia of the Alzheimer type (SDAT) has made progress within the field of pathology and to a certain extent in that of heredity. Within epidemiology, the search for risk factors is intensifying but the findings are still inconclusive. The present study of possible risk factors concentrates on environmental and personality factors. The total population of 2612 persons from a geographically delimited area, Lundby, two neighbouring parishes in southern Sweden, was examined in 1957 by one psychiatrist (Hagnell). A follow-up study of the same population, irrespective of domicile, was performed 15 years later, in 1972. Various precipitating as well as protective personality background factors were found to be significant for the outcome of SDAT, but no environmental factors appeared to be statistically significant in this cohort.

The findings from two recent Swedish retrospective studies on severely mentally retarded children born 1959-70 are surveyed. One study concerned an average county--Uppsala--in the middle of Sweden, the other a vast northern county, Västerbotten, with a sparse population. Figures for incidence and prevalence are given, as well as the percentage distribution of aetiological/pathogenic groups and subgroups, and the frequency of multihandicaps. Prenatal causes were apparent in about 70% of affected children, Down syndrome being the main condition (32%). A background of mutant genes in severe mental retardation was found significantly more often in Västerbotten than in Uppsala (17% and 7% respectively). Perinatal causes were revealed in 10 and 8% (9% of the two series pooled together) and postnatal causes in only 3 and 1% (2%). Associated CNS handicaps were present in about half of the children (42% in Uppsala and 52% in Västerbotten), with epilepsy in 30 and 36%, cerebral palsy in 18% and 19%, and a combination of epilepsy and cerebral palsy in 8 and 16%, respectively.