Henrik Dal

Autism Spectrum Disorders in the Stockholm Youth Cohort: Design, Prevalence and Validity

Objective Reports of rising prevalence of autism spectrum disorders (ASD), along with their profound personal and societal burden, emphasize the need of methodologically sound studies to explore their causes and consequences. We here present the design of a large intergenerational resource for ASD research, along with population-based prevalence estimates of ASD and their diagnostic validity. Method The Stockholm Youth Cohort is a record-linkage study comprising all individuals aged 0–17 years, ever resident in Stockholm County in 2001–2007 (N = 589,114). ASD cases (N = 5,100) were identified using a multisource approach, involving registers covering all pathways to ASD diagnosis and care, and categorized according to co-morbid intellectual disability. Prospectively recorded information on potential determinants and consequences of ASD were retrieved from national and regional health and administrative registers. Case ascertainment was validated through case-note review, and cross validation with co-existing cases in a national twin study. Results The 2007 year prevalence of ASD in all children and young people was 11.5 per 1,000 (95% confidence interval 11.2–11.8), with a co-morbid intellectual disability recorded in 42.6% (41.0–44.2) of cases. We found 96.0% (92.0–98.4) of reviewed case-notes being consistent with a diagnosis of ASD, and confirmed ASD in 85.2% (66.2–95.8) of affected twins. Conclusions Findings from this contemporary study accords with recently reported prevalence estimates from Western countries at around 1%, based on valid case ascertainment. The Stockholm Youth Cohort, in light of the availability of extensive information from Swedens registers, constitutes an important resource for ASD research. On-going work, including collection of biological samples, will enrich the study further.

Tanning habits and sunburn in a Swedish population age 13–50 years

As part of a skin cancer control programme, we studied the occurrence of self-reported outdoor tanning, sunbed use and ultraviolet (UV)-induced erythema in an urban area. A cross-sectional questionnaire study of 6000 adolescents aged 13-19 years, and 4000 adults aged 20-50 years was applied. Non-response was analysed for outdoor tanning and sunbed use. Results, in general, did not differ between responders and non-responders. Females aged 17-29 years tanned outdoors most frequently. Sunbed use and related erythema was twice as common in young females. In males, outdoor tanning was not age-related. In the past 12 months, 55% reported sunburn and/or burn from sunbed use, one-third were burned in Sweden, one-quarter on sunny resorts abroad. Sunburn occurs frequently. Compliance with recommendations for sunbed use is poor, especially among adolescents and young adults. To reduce the occurrence of erythema, the influence of risk settings upon behaviours is a critical issue for exploration.

Deviance in Fetal Growth and Risk of Autism Spectrum Disorder

OBJECTIVE Understanding the relationship between fetal growth and autism spectrum disorder (ASD) is likely to advance the search for genetic and nongenetic causes of ASD. The authors explored the associations between fetal growth, gestational age, and ASD with and without comorbid intellectual disability in a Scandinavian study population. METHOD The authors conducted a matched nested case-control study within the Stockholm Youth Cohort that included all children ages 0-17 who resided in Stockholm County from 2001 to 2007 (N=589,114). The authors identified 4,283 children with ASD: 1,755 with intellectual disability and 2,528 without, and they selected 36,588 age- and sex-matched comparison subjects. ASD case subjects were ascertained from unique identifiers assigned to all Swedish residents and linkage with official registers covering all pathways of assessment or care of ASD in Stockholm County. The authors calculated z scores of deviance in fetal growth from a reference curve using records from the national Swedish Medical Birth Registry, which included ultrasound dating of gestational age as well as birth weight. Crude and adjusted odds ratios for ASD, ASD with intellectual disability, and ASD without intellectual disability were the main outcome measures. RESULTS ASD risk increased with fetal growth 1.50 standard deviations below and >2.00 standard deviations above the mean for gestational age; the greatest risk was for fetal growth that was less than 2.00 standard deviations below the mean (adjusted odds ratio=1.70; 95% CI=1.44-2.01) or greater than 2.00 standard deviations above the mean (adjusted odds ratio=1.50; 95% CI=1.27-1.77). The same overall pattern was observed for ASD with and without intellectual disabilities. However, poor fetal growth (i.e., growth below the mean) was more strongly associated with ASD with intellectual disabilities than without. Regardless of fetal growth, preterm birth increased ASD risk. CONCLUSIONS Deviance in fetal growth at either distributional extreme may be a significant antecedent to the development of ASD through genetic and/or nongenetic mechanisms.

Swedish pre-school children's UVR exposure: a comparison between two outdoor environments

Background: Overexposure to ultraviolet radiation (UVR) in childhood is a major risk factor for skin cancer. Shady environments are recommended as one method of protection.

Sunbed use among Swedish adolescents in the 1990s: a decline with an unchanged relationship to health risk behaviors

Aims: Sunbed use is common among adolescents, and may give an increment to UV exposure and an overall skin cancer risk comparable to that of the sun. Sunbed use was studied among 15- to 19-year-old adolescents in Stockholm County. Methods: Data from two questionnaire surveys (1,252 respondents in 1993, and 2,950 respondents in 1999, survey tool partly revised) were analysed. By stepwise binary logistic regression the occurrence of sunbed use was assessed and analysed versus sunbed erythema, skin type, outdoor tanning, sunscreen use and smoking. Results: Sunbed use declined between the surveys. In 1993, 70% of females, and 44% of males used sunbeds; in 1999, these were 45% and 19% respectively. Sunbeds were used against user recommendations. Of the sunbed users in 1993, 45% and 43% reported sunbed erythema; in 1999, 29% and 19% did so. Sunbed erythema, though related to sun sensitivity, occurred in all skin types. In both surveys, sunbed use was positively related to moderately sensitive skin type (females), outdoor tanning, and smoking (females). Smoking was a strong predictor for sunbed use among females in both surveys. Conclusions: Even though different survey tools were used, and in spite of a decline in sunbed use, sunbed erythema was still common, and the relation to other health risk behaviour remained. Further research on sunbed use and its role in the aggregation of health risk behaviours in vulnerable ages is warranted, particularly its relation to outdoor tanning and smoking. A national and international harmonization of survey tools is also recommended for improved comparability.

Refugee migration and risk of schizophrenia and other non-affective psychoses: cohort study of 1.3 million people in Sweden.

Objective To determine whether refugees are at elevated risk of schizophrenia and other non-affective psychotic disorders, relative to non-refugee migrants from similar regions of origin and the Swedish-born population. Design Cohort study of people living in Sweden, born after 1 January 1984 and followed from their 14th birthday or arrival in Sweden, if later, until diagnosis of a non-affective psychotic disorder, emigration, death, or 31 December 2011. Setting Linked Swedish national register data. Participants 1 347 790 people, including people born in Sweden to two Swedish-born parents (1 191 004; 88.4%), refugees (24 123; 1.8%), and non-refugee migrants (132 663; 9.8%) from four major refugee generating regions: the Middle East and north Africa, sub-Saharan Africa, Asia, and Eastern Europe and Russia. Main outcome measures Cox regression analysis was used to estimate adjusted hazard ratios for non-affective psychotic disorders by refugee status and region of origin, controlling for age at risk, sex, disposable income, and population density. Results 3704 cases of non-affective psychotic disorder were identified during 8.9 million person years of follow-up. The crude incidence rate was 38.5 (95% confidence interval 37.2 to 39.9) per 100 000 person years in the Swedish-born population, 80.4 (72.7 to 88.9) per 100 000 person years in non-refugee migrants, and 126.4 (103.1 to 154.8) per 100 000 person years in refugees. Refugees were at increased risk of psychosis compared with both the Swedish-born population (adjusted hazard ratio 2.9, 95% confidence interval 2.3 to 3.6) and non-refugee migrants (1.7, 1.3 to 2.1) after adjustment for confounders. The increased rate in refugees compared with non-refugee migrants was more pronounced in men (likelihood ratio test for interaction χ2 (df=2) z=13.5; P=0.001) and was present for refugees from all regions except sub-Saharan Africa. Both refugees and non-refugee migrants from sub-Saharan Africa had similarly high rates relative to the Swedish-born population. Conclusions Refugees face an increased risk of schizophrenia and other non-affective psychotic disorders compared with non-refugee migrants from similar regions of origin and the native-born Swedish population. Clinicians and health service planners in refugee receiving countries should be aware of a raised risk of psychosis in addition to other mental and physical health inequalities experienced by refugees.

Brief Report: Maternal Smoking during Pregnancy and Autism Spectrum Disorders.

Prenatal exposure to tobacco smoke is suggested as a potential risk factor for autism spectrum disorders (ASD). Previous epidemiological studies of this topic have yielded mixed findings. We performed a case–control study of 3,958 ASD cases and 38,983 controls nested in a large register-based cohort in Sweden. ASD case status was measured using a multisource case ascertainment system. In adjusted results, we found that maternal smoking during pregnancy is not associated with increased risk of ASD regardless of presence or absence of comorbid intellectual disability. Apparent associations were attributable to confounding by sociodemographic characteristics of parents such as education, income, and occupation.

Trends during a half century in relative squamous cell carcinoma distribution by body site in the Swedish population: Support for accumulated sun exposure as the main risk factor

There is a strong relationship between squamous cell carcinoma (SCC) and exposure to ultraviolet radiation in terms of accumulated exposure. In this study, data from the Swedish Cancer Registry are surveyed to discern a reflection of behavioral and societal changes in relative distribution of SCC by body site. Data for the time period 1960–2004, including a total of 66 221 cases (56 669 people) were analyzed by body site for age and gender cohorts. The age‐standardized (European population) incidence per 100 000 of SCC in the year 2004 was 30.4 in males and 15.4 in females. In the year 1960, the corresponding incidences were 7.7 and 3.8; that is, SCC has become four times more frequent in Sweden for both sexes during this period. The standardized incidence of SCC increased on all body sites except eyelids (men and women) and ears (women). Head tumors dominated among patients aged 70 years or more and diagnosed 1960–1964. Among patients less than 70 years old at diagnosis in 2000–2004, tumors of the trunk and limbs dominated. A relative increase of tumors of the scalp and neck was observed in all age groups (men), and of tumors of the trunk and upper limbs in all age groups and both sexes except among patients aged more than 90 years of age. In contrast, a relative decrease of tumors on the face (including the ears) was seen in all age groups. The relative increase of SCC of the trunk and upper limbs is a plausible reflection of intentional tanning.

Recent time trends in levels of self‐reported anxiety, mental health service use and suicidal behaviour in Stockholm

Kosidou K, Magnusson C, Mittendorfer‐Rutz E, Hallqvist J, Gumpert CH, Idrizbegovic S, Dal H, Dalman C. Recent time trends in levels of self‐reported anxiety, mental health service use and suicidal behaviour in Stockholm.

Sun habits in kidney transplant recipients with skin cancer: a case-control study of possible causative factors.

Organ transplant recipients are frequently affected by skin cancer, which might also be a major cause of long-term mortality. Excessive sun exposure is considered to be a factor in the aetiology, but uncertainty about the importance of this and other proposed risk factors remains. The purpose of this study was to investigate sun behaviour before and/or after the transplantation in kidney transplant recipients with or without cutaneous squamous cell carcinoma. A nested, population-based, case-control study was carried out on 95 kidney transplant recipients who had contracted cutaneous squamous cell carcinoma after the transplantation and on an accurately matched control population of 154 kidney transplanted patients. Information on sun exposure before and after the transplantation, skin type, use of sunbeds, warts, etc., was obtained from a questionnaire which contained 38 detailed questions. The differences between cases and control subjects were not significant for sun exposure before or after the transplantation, sun protective measures, number of sunburns, outdoor occupation, smoking habits or use of sunbeds. Compared to patients with skin type IV, the cutaneous squamous cell carcinoma odds ratio was 3.0 (95% CI = 1.3-7.0) for skin type I + II. Patients with light blond or red hair colour also had a higher odds ratio than those with dark hair, 3.2 (95% CI = 1.2-8.2), and patients with warts after the transplantation had a higher odds ratio than those without, 2.2 (95% CI = 1.2-4.2). In conclusion, poor tanning ability rather than the amount of sun exposure is associated with the development of cutaneous squamous cell carcinoma in kidney transplant recipients and warts appearing after the transplantation indicate increased risk.