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SEX DIFFERENCES IN AGE AT FIRST ONSET OF SCHIZOPHRENIC DISORDERS

H. Hlfner, A. Reicher, K. Maurer, W. Loffler and P. Munk-Jorgensen

Central Institute of Mental Health, 55 P.O. Box 5970, D-6800 Man- nheim, FRG

Sex differences in age at first hospitalization are among the most consistent epidemiological findings in schizophrenic disorders: males seem to be admitted about five to ten years prior to females.

The aim of the project, conducted in collaboration with the Institute of Psychiatric Demography in Aarhus, Denmark (Head: Dr. Munk-Jorgen- sen), is to confirm these results on population-based age-related rates and to test them for their sociocultural and transcultural stability. The analyses so far conducted are based on data available from the Mannheim (West Germany) and Aarhus (Denmark) Case Register. Included were all Mannheim citizens who in 1979/80 and all Danish citizens who in 1976 were admitted to a psychiatric institution with a main diagnosis of schizophrenia or paranoid psychosis for the first time (295.0-295.9, 297.0-297.9, 298.3, 301.83 according to ICD-8). These criteria were met by 658 male and 709 female Danish and by 108 male and 116 female Mannheim patients. Preliminary results seem to confirm the epidemiological findings: when the diagnosis of schizophrenic or paranoid psychosis is given for the first time, in Denmark the average age is 33.3 years for males and 39.4 years for females; in Mannheim the average age is 31.9 years for males and 37.2 years for females. These sex-specific age differences of 5.3-6.1 years (Ma/De) remain very stable at 5.0-5.8 years (Ma/De), when a more restricted diagnosis - i.e. ICD 295 only- is used. Age-specific first-admission rates also show a peak which is markedly earlier in males than in females in both countries.

The sex differences persist, even if occupational status is taken into account: working males are admitted 3.4 years earlier than working females, unemployed males '6.4 years earlier than unemployed females (Ma). Age differences become smaller when family status is considered, but single males are still significantly (2.5 years) younger than single females, and married males significantly younger (3.3 years) than married females (De).

In addition, men seem to be younger than women not only at first admission for a diagnosis of schizophrenic or paranoid psychosis but also at first admission to a psychiatric institution prior to that episode. This latter group, which has one or more hospital admissions for other diagnoses beforehand, comprises about one-third of patients in both sexes. The time lag between first psychiatric admission and the first admission for a schizophrenic or paranoid diagnosis is at 2-3 years also very similar in both sexes (2.9 years for Danish men and 3.0 years for Danish women; 2.1 years for Mannheim men and 2.7 years for Mannheim women). In both males and females, the most frequent diagnoses at prior episodes were 'personality disorder' and 'neurosis' (46.3% males and 47.8% females) followed by 'affective psychosis' and 'reactive psychosis' (25.6% male and 28.1% female patients) (De). The results suggest that sex differences in age at first admission are due to a summation of several factors. In further steps of the project, sex differences in first onset of symptomatology and the possible underlying causes will be investigated.