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Mild mental retardation in children in a northern Swedish county
Insights
This study analyzed 171 children with mild mental retardation in Sweden, finding a decreasing incidence and a significant male excess. Genetic factors were identified in 31% of cases, with unknown etiology in 43%.
Area of Science:
- Pediatrics
- Genetics
- Epidemiology
Background:
- Mild mental retardation (IQ 50-69) affects a significant population, with etiological factors often complex and multifactorial.
- Understanding the incidence, trends, and causes of mild mental retardation is crucial for public health interventions and support services.
Purpose of the Study:
- To retrospectively analyze the incidence, etiology, and associated factors of mild mental retardation in a defined Swedish population.
- To identify trends in the incidence of mild mental retardation over an 11-year period.
Main Methods:
- Retrospective analysis of 171 children diagnosed with mild mental retardation (IQ 50-69) born between 1959-1970 in a northern Swedish county.
- Data collection from the Board for Provisions and Services to the Mentally Retarded, including etiological factors, birth characteristics, and associated handicaps.
Main Results:
- The mean annual incidence of mild mental retardation decreased from 1959-1970, with an overall rate of 4.2 per 1000 live births.
- A male excess (1.8:1) was observed across all etiological groups. Prenatal causes accounted for 43%, genetic factors for 31% (chromosomal, mutant gene, multifactorial), and etiology remained unknown in 43%.
- Thirty percent of children had associated central nervous system (CNS) handicaps, with epilepsy being the most common (16%). Ten children showed significant intellectual progress, no longer requiring specialized services.
Conclusions:
- Mild mental retardation in this cohort had a multifactorial etiology, with a notable proportion attributed to genetic and unknown factors.
- The decreasing incidence suggests potential improvements in prenatal care or other unidentified factors. The male predominance warrants further investigation.
- Associated CNS handicaps, particularly epilepsy, are common comorbidities, highlighting the need for comprehensive care and support for affected children.
Abstract:
A series of children with mild mental retardation (171 children, IQ 50-69) born in 1959-1970 in a northern Swedish county and registered by the Board for Provisions and Services to the Mentally Retarded were analysed retrospectively. The mean annual incidence of mild mental retardation in registered children alive at the age of one year decreased during the period 1959-1970 and for the whole period was 4.2 per 1000, compared with 3.9 per 1000 for severe mental retardation in the same period of time and area. Ten children once classified as mildly mentally retarded made considerable intellectual progress and after some time no longer needed special help from the authorities. There was a pronounced male excess in the total series (1.8:1) and in all the main aetiological groups. Only small differences were found in mean birth weights, gestational age and maternal age in the main aetiological groups. In the series as a whole, however, there was an increased frequency of children small for gestational age. Prenatal causes were considered relevant in 43 per cent, perinatal in 7 per cent, and postnatal in 5 per cent. In 2 per cent there was a psychosis. In 43 per cent the aetiology could not be traced. Genetic causes were found in 31 per cent; in 8 per cent there was a chromosomal aetiology, in a further 8 per cent a mutant gene disorder and in 15 per cent the aetiology were considered multifactorial, i.e. at least one first-degree relative also had mental retardation and in both cases the cause of the retardation was unknown. Thirty per cent of the children had associated CNS handicaps, epilepsy (16 per cent) being the most frequent.