Systematic review and collaborative recalculation of 133,693 incident cases of schizophrenia.

BACKGROUND: This systematic review and collaborative recalculation was set up to recalculate schizophrenia incidence rates from previously published studies by age and sex. METHOD: PubMed, EMBASE and PsycINFO databases were searched (January 1950 to December 2009) for schizophrenia incidence studies. Numerator and population data were extracted by age, sex and, if possible, study period. Original data were requested from the authors to calculate age- and sex-specific incidence rates. Incidence rate ratios (IRRs) with their 95% confidence intervals (CIs) were computed by age and sex from negative binomial regression models. RESULTS: Forty-three independent samples met inclusion criteria, yielding 133 693 incident cases of schizophrenia for analysis. Men had a 1.15-fold (95% CI 1.00-1.31) greater risk of schizophrenia than women. In men, incidence peaked at age 20-29 years (median rate 4.15/10,000 person-years, IRR 2.61, 95% CI 1.74-3.92). In women, incidence peaked at age 20-29 (median rate 1.71/10,000 person-years, IRR 2.34, 95% CI 1.66-3.28) and 30-39 years (median rate 1.24/10,000 person-years, IRR 2.25, 95% CI 1.55-3.28). This peak was followed by an age-incidence decline up to age 60 years that was stronger in men than in women (χ² = 57.90, p < 0.001). The relative risk of schizophrenia was greater in men up to age 39 years and this reversed to a greater relative risk in women over the age groups 50-70 years. No evidence for a second incidence peak in middle-aged women was found. CONCLUSIONS: Robust sex differences exist in the distribution of schizophrenia risk across the age span, suggesting differential susceptibility to schizophrenia for men and women at different stages of life.

Mortality in first-contact psychosis patients in the U.K.: a cohort study.

BACKGROUND: The excess mortality following first-contact psychosis is well recognized. However, the causes of death in a complete incidence cohort and mortality patterns over time compared with the general population are unknown. METHOD: All 2723 patients who presented for the first time with psychosis in three defined catchment areas of the U.K. in London (1965-2004, n=2056), Nottingham (1997-1999, n=203) and Dumfries and Galloway (1979-1998, n=464) were traced after a mean of 11.5 years follow-up and death certificates were obtained. Data analysis was by indirect standardization. RESULTS: The overall standardized mortality ratio (SMR) for first-contact psychosis was 184 [95% confidence interval (CI) 167-202]. Most deaths (84.2%, 374/444) were from natural causes, although suicide had the highest SMR (1165, 95% CI 873-1524). Diseases of the respiratory system and infectious diseases had the highest SMR of the natural causes of death (232, 95% CI 183-291). The risk of death from diseases of the circulatory system was also elevated compared with the general population (SMR 139, 95% CI 117-164) whereas there was no such difference for neoplasms (SMR 111, 95% CI 86-141). There was strong evidence that the mortality gap compared with the general population for all causes of death (p<0.001) and all natural causes (p=0.01) increased over the four decades of the study. There was weak evidence that cardiovascular deaths may be increasing relative to the general population (p=0.07). CONCLUSIONS: People with first-contact psychosis have an overall mortality risk that is nearly double that of the general population. Most excess deaths are from natural causes. The widening of the mortality gap over the last four decades should be of concern to all clinicians involved in delivering healthcare.

Incidence of schizophrenia in south-east London between 1965 and 1997.

BACKGROUND: There has been much debate about changes in the incidence of schizophrenia. AIMS: To identify any changes in incidence of schizophrenia in Camberwell, south-east London, between 1965 and 1997. METHOD: Research Diagnostic Criteria and DSM-III-R diagnoses were generated for all first contacts by the OPCRIT computer program, and incidence rates of schizophrenia in seven time periods were measured. Indirect standardisation and Poisson models were used to measure the effect of time period and to examine interactions with age and gender. RESULTS: There was a continuous and statistically significant increase in the incidence of schizophrenia, which was greatest in people under 35 years of age and was not gender-specific. CONCLUSIONS: The incidence of schizophrenia has doubled in south-east London over the past three decades.

Incidence of schizophrenia in ethnic minorities in London: ecological study into interactions with environment.

OBJECTIVE: To determine whether the incidence of schizophrenia among people from non-white ethnic minorities is greater in neighbourhoods where they constitute a smaller proportion of the total population. DESIGN: Ecological design including retrospective study of case records to calculate the incidence of schizophrenia in the ethnic minority population across electoral wards and multi-level analysis to examine interaction between individuals and environment. SETTING: 15 electoral wards in Camberwell, South London. PARTICIPANTS: All people aged 16 years and over who had contact with psychiatric services during 1988-97. MAIN OUTCOME MEASURE: Incidence rates of schizophrenia according to Research Diagnostic Criteria. RESULTS: The incidence of schizophrenia in non-white ethnic minorities increased significantly as the proportion of such minorities in the local population fell. The incidence rate ratio varied in a dose-response fashion from 2.38 (95% confidence interval 1.49 to 3.79) in the third of wards where non-white ethnic minorities formed the largest proportion (28-57%) of the local population to 4.4 (2.49 to 7.75) in the third of wards where they formed the smallest proportion (8-22%). CONCLUSION: The incidence of schizophrenia in non-white ethnic minorities in London is greater when they comprise a smaller proportion of the local population.

Comparison of the incidence of schizophrenia in rural Dumfries and Galloway and urban Camberwell.

BACKGROUND: Being born or living in urban areas is associated with high rates of schizophrenia. However, few studies have compared the incidence in urban/rural areas using the same methodology. AIMS: To compare service-based incidence rates for schizophrenia in rural Dumfries and Galloway in south-west Scotland with urban Camberwell in south-east London. METHOD: Using Research Diagnostic Criteria diagnoses from the OPCRIT computer algorithm, we compared the incidence of schizophrenia over 12 years (1979-1984 and 1992-1997) using indirect standardisation techniques and Poisson regression modelling. RESULTS: The incidence was 61% higher in urban Camberwell than in rural Dumfries and Galloway (standardised incidence ratio (SIR)=1.61; 95% CI=1.42-1.81). There was no difference in incidence when we compared the White population in Camberwell with Dumfries and Galloway (SIR=1.12; 95% CI=0.86-1.43). CONCLUSIONS: The incidence of schizophrenia in urban Camberwell was higher than that in rural Dumfries and Galloway; the high incidence of non-Whites in Camberwell largely explains the urban/rural difference.

Nithsdale Schizophrenia Surveys. 20. Cognitive function in a catchment-area-based population of patients with schizophrenia.

BACKGROUND: Cognitive deficits are a core aspect of schizophrenia but there has been no study of cognitive function in a catchment-area-based population of patients with schizophrenia. AIMS: To assess cognitive function in a population of patients with schizophrenia, and relate it to community functioning. METHOD: All patients with schizophrenia in Nithsdale, south-west Scotland, were identified (n = 182). Measures of assessment were: National Adult Reading Test (NART), Mini-Mental State Examination (MMSE), Rivermead Behavioural Memory Test (RBMT), Executive Interview (EXIT), FAS Verbal Fluency and Health of the Nation Outcome Scales (HoNOS). RESULTS: We assessed 138 patients, mean age 48 years (standard deviation (s.d.) 15). Only 14% were in-patients. The mean premorbid IQ as assessed by NART was 98 (s.d. 14); 15% of patients had significant global cognitive impairment (MMSE); 81% had impaired memory (RBMT); 25% had executive dyscontrol (EXIT); and 49% had impaired verbal fluency (FAS). Scores on the functional impairment sub-scale of HoNOS correlated with all measures of cognitive impairment. CONCLUSIONS: Cognitive dysfunction is pervasive in a community-based population of patients with schizophrenia.

Schizophrenia is not disappearing in south-west Scotland.

BACKGROUND: Recent work has reported a decline in the incidence of schizophrenia, but it is unclear if these findings reflect a true decrease in its incidence or are an artefact arising from methodological difficulties. AIMS: To take account of these methodological difficulties and report service-based incidence rates for schizophrenia in Dumfries and Galloway in south-west Scotland for 1979-98. METHOD: Using both clinical diagnoses and diagnoses generated from the Operational Checklist for Psychotic Disorders (OPCRIT) computer algorithm for ICD-10 and DSM-IV schizophrenia, we measured change in the incidence rates over time. We used indirect standardisation techniques and Poisson models to measure the rate ratio linear trend. RESULTS: There was a monotonic and statistically significant decline in clinically diagnosed schizophrenia. The summary rate ratio linear trend was 0.77. However, using OPCRIT-generated ICD-10 and DSM-IV diagnoses, there was no significant difference over time. CONCLUSIONS: OPCRIT-generated consistent diagnoses revealed no significant fall in the incidence of schizophrenia. Changes in diagnostic practice have caused the declining rates of clinically diagnosed schizophrenia in Dumfries and Galloway.

Nithsdale schizophrenia surveys 21: a longitudinal study of National Adult Reading Test stability.

BACKGROUND: The stability of the National Adult Reading Test (NART) as a measure of pre-morbid intelligence in schizophrenia has not yet been satisfactorily established despite the widespread use of the NART in schizophrenia research. METHOD: We examined NART stability in a diverse group of 45 schizophrenic patients in a prospective longitudinal study over 6.5-7.5 years. RESULTS: The results showed that NART performance does not decline significantly with increasing duration of schizophrenic illness and that test-retest reliability, even over 6.5-7.5 years, is extremely high. DISCUSSION: Our results provide the necessary evidence that the NART can be used as a stable measure of pre-morbid intelligence in schizophrenia.