Design choices when estimating the treated incidence of schizophrenia

Incidence of non-affective psychotic disorders in refugees and peers growing up in Denmark and Sweden: a registry linkage study

PURPOSE

Higher rates of non-affective psychotic disorders (NAPD) in minority groups have been reported in many countries. However, few studies have explored how rates differ between refugees and other minority groups and none with an international comparative angle. A comparative perspective makes it possible to relate group differences to aspects national context that underpin the social determinants of disease.

METHODS

We compared the incidence of treated NAPD among youth born in or who immigrated to Denmark/Sweden before turning 18. Youth aged 18-35 during 2006-2018 were included (NDenmark/NSweden = 1,606,423/2,614,721) and were followed until first NAPD treatment (cases [Denmark/Sweden] = 12,193/9,641), 36th birthday, emigration or death. Incidence rates (IR) and ratios (IRR) comparing refugees, non-refugee migrants, descendants of non-refugee migrants and majority youth were obtained through Poisson regression on data aggregated by country, sex and age, contrasted by sex and country. Complementary analyses on individual-level data adjusting for further socio-demographic factors were conducted in each country separately.

RESULTS

Incidence rates were higher in all groups compared with the majority group (IRRrange = 1.4-2.9, 95% CI[min, max] = 1.2-3.1). Relative differences between the three minority groups were smaller (IRRrange = 0.7-1.0, 95% CI[min, max] = 0.5-1.2). Although incidence rates were higher in Denmark than Sweden, relative group differences were similar.

CONCLUSION

Exposures shared between young refugees and other minority groups growing up in Denmark and Sweden may be especially important for their excess risk of NAPD. Further studies should investigate the mechanisms behind the elevated rates in minority groups with special paid attention to factors such as discrimination, social exclusion and acculturation stress.

Association between Arachidonic Acid and the Risk of Schizophrenia: A Cross-National Study and Mendelian Randomization Analysis

Polyunsaturated fatty acids (PUFAs), especially long-chain PUFAs (LCPUFAs), are crucial for both the structural and functional integrity of cells. PUFAs have been reported to be insufficient in schizophrenia, and the resulting cell membrane impairments have been hypothesized as an etiological mechanism. However, the impact of PUFA deficiencies on the onset of schizophrenia remain uncertain. We investigated the associations between PUFAs consumption and schizophrenia incidence rates through correlational analyses and conducted Mendelian randomization analyses to reveal the causal effects. Using dietary PUFA consumption and national schizophrenia incidence rates in 24 countries, we found that incidence rates of schizophrenia were inversely correlated with arachidonic acid (AA) and ω-6 LCPUFA consumption (rAA = -0.577, p < 0.01; rω-6 LCPUFA = -0.626, p < 0.001). Moreover, Mendelian randomization analyses revealed that genetically predicted AA and gamma-linolenic acid (GLA) were protective factors against schizophrenia (ORAA = 0.986, ORGLA = 0.148). In addition, no significant relationships were observed between schizophrenia and docosahexaenoic acid (DHA) or other ω-3 PUFAs. These findings show that the deficiencies of ω-6 LCPUFAs, especially AA, are associated with schizophrenia risk, which sheds novel insight into the etiology of schizophrenia and a promising diet supplementation for the prevention and treatment of schizophrenia.

Universal healthcare coverage for first episode of schizophrenia-spectrum disorders in Chile: analysis of the administrative database

Aim of the study was to analyse the Ministry of Health's (MINSAL) administrative database of the Universal Health Coverage (UHC) program for First Episode of Schizophrenia Spectrum Disorders (FEP-SSD). The database included every case registered in the program between 2004 and 2017. According to the timeframes established for permanence in the program, cases were defined as Suspected, FEP in diagnostic observation and FEP-SSD. Only first registers were analysed. We compared gender, age at entry, level of care and region where the case was registered. Denominator data for estimation of incidence rates were obtained from the last census. We adjusted incidence rate ratios by age, gender, and region. During the studied period, 33.207 suspected cases were registered. 27.006 (81%) were confirmed as FEP and after 6-month follow-up, 22.701 (68%) were confirmed as FEP-SSD. The median age at entry was 24 years, males entering at younger age. Male proportion was higher than female in all groups. 46.9% of all cases were detected in primary care. FEP-SSD cases were six years younger and had a higher proportion of males than discarded cases (62.6 vs 53.2%). During 169.4 million person-years at risk, crude incidence for suspected cases was 19.58 per 100.000 person-years; for FEP, 15.92 per 100.000 person-years and for FEP-SSD, 13.38 per 100.000 person-years. Chile has lower incidence of FEP-SSD compared to current world estimations but gender proportions are comparable. This UHC program has allowed early access through the integration of mental health to the health network at all levels of care.

The impact of study design on schizophrenia incidence estimates: A systematic review of Northern European studies 2008-2019

The best estimates of the incidence of schizophrenia range more than 25-fold from 3 to 80 per 100,000 person-years. To what extent do differences in study design explain this wide variation? We selected all studies published between 2008-2019 reporting the incidence of schizophrenia in general populations of Northern Europe. We identified 17 estimates covering 85 million person-years and more than 15,000 individual cases. The estimates ranged from 4-72 per 100,000 person-years (median 30; interquartile range 13-41). We classified the estimates in terms of three study design factors (coverage of services, time frame, and diagnostic quality) and two population factors (urbanicity and age). A meta-regression model of the three design factors, using the two population factors as covariates, explained 91% of between-study variation. Studies performed in general psychiatric services reported similar estimates [incidence rate ratio 1.12 (95% confidence interval 0.88 to 1.43)] to those performed in specialized services. But studies applying a cumulative time frame to diagnosis reported fourfold higher estimates [4.04 (3.14 to 5.2)] than those applying a first-contact time frame. And studies based on clinical diagnoses reported lower estimates [0.55 (0.43 to 0.72)] than those based on standardized research diagnoses. The three study design factors by themselves explained 67% of between-study variation. When comparing incidence rates from different populations, distorsions arising from differences in study design can eclipse differences caused by schizophrenia risk factors, such as gender, age or migrant status.

Estimated Proportions and Characteristics of National Survey Respondents Reporting New Diagnoses of Schizophrenia or Other Psychoses in the Past Year as Compared With Prior Years

Epidemiologic data on first-episode psychosis is limited due to the infrequency of cases in the general population. This study uses the National Epidemiologic Survey on Alcohol and Related Conditions-III (N = 36,309) to examine population-based estimates of early psychosis based on adults who report a first-time diagnosis of schizophrenia from a doctor in the past year and compares them with those receiving diagnoses in previous years. Altogether, 60 respondents reported past-year schizophrenia (170 per 100,000) or 6.7% of 901 with any reported schizophrenia. Mean age was 41.4 ± 2.1, and they reported significantly higher rates of any past-year substance use disorder (44.7%) than individuals diagnosed in previous years (27.7%), specifically alcohol use disorder. Compared with other samples (many of which excluded older adults), this study suggests that early psychosis may affect older populations more than previously recognized, but comorbidity with substance use disorders showed similar elevations.