Michael Lundberg

Parental socioeconomic status and risk of offspring autism spectrum disorders in a Swedish population-based study.

OBJECTIVE Epidemiological studies in the United States consistently find autism spectrum disorders (ASD) to be overrepresented in high socioeconomic status (SES) families. These findings starkly contrast with SES gradients of many health conditions, and may result from SES inequalities in access to services. We hypothesized that prenatal measures of low, not high, parental SES would be associated with an increased risk of offspring ASD, once biases in case ascertainment are minimized. METHOD We tested this hypothesis in a population-based study in Sweden, a country that has free universal healthcare, routine screening for developmental problems, and thorough protocols for diagnoses of ASD. In a case-control study nested in a total population cohort of children aged 0 to 17 years living in Stockholm County between 2001 and 2007 (N = 589,114), we matched ASD cases (n = 4,709) by age and sex to 10 randomly selected controls. We retrieved parental SES measures collected at time of birth by record linkage. RESULTS Children of families with lower income, and of parents with manual occupations (OR = 1.4, 95% CI = 1.3-1.6) were at higher risk of ASD. No important relationships with parental education were observed. These associations were present after accounting for parental ages, migration status, parity, psychiatric service use, maternal smoking during pregnancy, and birth characteristics; and regardless of comorbid intellectual disability. CONCLUSIONS Lower, not higher, socioeconomic status was associated with an increased risk of ASD. Studies finding the opposite may be underestimating the burden of ASD in lower SES groups.

Migration and autism spectrum disorder: population-based study {

BACKGROUND Migration has been implicated as a risk factor for autism, but evidence is limited and inconsistent. AIMS To investigate the relationship between parental migration status and risk of autism spectrum disorder, taking into consideration the importance of region of origin, timing of migration and possible discrepancies in associations between autism subtypes. METHOD Record-linkage study within the total child population of Stockholm County between 2001 and 2007. Individuals with high- and low-functioning autism were defined as having autism spectrum disorder with and without comorbid intellectual disability, and ascertained via health and habilitation service registers. RESULTS In total, 4952 individuals with autism spectrum disorder were identified, comprising 2855 children with high-functioning autism and 2097 children with low-functioning autism. Children of migrant parents were at increased risk of low-functioning autism (odds ratio (OR) = 1.5, 95% CI 1.3-1.7); this risk was highest when parents migrated from regions with a low human development index, and peaked when migration occurred around pregnancy (OR = 2.3, 95% CI 1.7-3.0). A decreased risk of high-functioning autism was observed in children of migrant parents, regardless of area of origin or timing of migration. Parental age, income or obstetric complications did not fully explain any of these associations. CONCLUSIONS Environmental factors associated with migration may contribute to the development of autism presenting with comorbid intellectual disability, especially when acting in utero. High- and low-functioning autism may have partly different aetiologies, and should be studied separately.

Parental age and the risk of autism spectrum disorders: findings from a Swedish population-based cohort

BACKGROUND The objectives of this study were to examine the independent and dependent associations of maternal and paternal age and risk of offspring autism spectrum disorders (ASD), with and without intellectual disability (ID). METHODS The sample consisted of 417 303 Swedish children born 1984-2003. ASD case status (N = 4746) was ascertained using national and regional registers. Smoothing splines in generalized additive models were used to estimate associations of parental age with ASD. RESULTS Whereas advancing parental age increased the risk of child ASD, maternal age effects were non-linear and paternal age effects were linear. Compared with mothers at the median age 29 years, those <29 had similar risk, whereas risk increased after age 30, with an odds ratio (OR) of 1.75 [95% (CI): 1.63-1.89] at ages 40-45. For fathers, compared with the median age of 32 years, the OR for ages 55-59 was 1.39 (1.29-1.50). The risk of ASD was greater for older mothers as compared with older fathers. For example, mothers aged 40-45 (≥97.2th percentile) had an estimated 18.63 (95% CI: 17.25-20.01) ASD cases per 1000 births, whereas fathers aged 55-59 (≥99.7th percentile) had 16.35 (95% CI: 15.11-17.58) ASD cases per 1000 births. In analyses stratified by co-parental age, increased risk due to advancing paternal age was evident only with mothers ≤35 years. In contrast, advancing maternal age increased risk regardless of paternal age. Advancing parental age was more strongly associated with ASD with ID, compared with ASD without ID. CONCLUSIONS We confirm prior findings that advancing parental age increases risk of ASD, particularly for ASD with ID, in a manner dependent on co-parental age. Although recent attention has emphasized the effects of older fathers on ASD risk, an increase of n years in maternal age has greater implications for ASD risk than a similar increase in paternal age.

Socioeconomic status and risk of psychological distress and depression in the Stockholm Public Health Cohort: A population-based study

BACKGROUND There is limited evidence whether the association between low socioeconomic status and risk of common mental disorders varies with symptom severity, type of socioeconomic indicator or gender. METHODS A population-based survey was conducted among a random sample of Stockholm County residents aged 18-84 years in 2002. Respondents were reassessed via a follow-up questionnaire in 2007. Participants in both surveys (n = 23794) were categorized according to socioeconomic status at baseline and followed up for onset of psychological distress (according to the twelve-item general health questionnaire) and depression (according to health data registers). Logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS Occupational class was not associated with risk of psychological distress, regardless of severity or gender. Occupational class was strongly associated with onset of depression in men (OR 3.0 [95% CI 1.5-5.9], comparing unskilled manual workers with higher non-manual workers) but not women. Income was associated with risk of onset of all outcomes, and risks increased with symptom severity. Belonging to the highest household income category was particularly protective of depression in women. Education was unrelated to either outcome in men and women overall. LIMITATIONS Retention rate at follow-up was 76% and depression was ascertained via health service use. CONCLUSION Low socioeconomic position is associated with onset of depression but not mild distress. Attributes of occupational class and household income may be respectively more relevant for the development of depression in men and women.

Psychological distress and risk of long-term disability: population-based longitudinal study

Background Common mental disorders are known to cause long-term disability, although not much is known about long-term consequences of milder forms of psychological distress. Objective To investigate the association between increasing levels of psychological distress and 5-year risk of long-term disability pensions awarded for somatic or psychiatric conditions. Methods In this longitudinal population-based study, a cohort of 17 205 individuals, aged 18–64 years, recruited in 2002 in Stockholm County was prospectively followed up for new disability pension awards. The 12-item General Health Questionnaire (GHQ-12) was used to measure baseline psychological distress, and participants were categorised as having no, mild, moderate or severe psychological distress (GHQ-12 scores of 0; 1–2; 3–7 and 8–12, respectively). Details of new disability pension awards were obtained through record linkage with the Swedish National Insurance register. Comprehensive information on a range of sociodemographic, lifestyle and health characteristics was available. Results Increasing levels of psychological distress at baseline were associated with an increased likelihood of obtaining a disability pension later in life. Even mild psychological distress was independently associated with the award of a disability pension for both somatic (HR=1.7; 95% CI 1.3 to 2.2) and psychiatric diagnoses (2.2; 1.4 to 3.6). Over a quarter of disability pensions awarded for a somatic diagnosis, and almost two-thirds awarded for a psychiatric diagnosis, could be attributed to psychological distress. Conclusions Mild psychological distress may be associated with more long-term disability than previously acknowledged and its public health importance may be underestimated.

Parental share in public and domestic spheres: a population study on gender equality, death, and sickness

Study objective: Examine the relation between aspects of gender equality and population health based on the premise that sex differences in health are mainly caused by the gender system. Setting/participants: All Swedish couples (98 240 people) who had their first child together in 1978. Design: The exposure of gender equality is shown by the parents’ division of income and occupational position (public sphere), and parental leave and temporary child care (domestic sphere). People were classified by these indicators during 1978–1980 into different categories; those on an equal footing with their partner and those who were traditionally or untraditionally unequal. Health is measured by the outcomes of death during 1981–2001 and sickness absence during 1986–2000. Data are obtained by linking individual information from various national sources. The statistical method used is multiple logistic regressions with odds ratios as estimates of relative risks. Main results: From the public sphere is shown that traditionally unequal women have decreased health risks compared with equal women, while traditionally unequal men tend to have increased health risks compared with equal men. From the domestic sphere is indicated that both women and men run higher risks of death and sickness when being traditionally unequal compared with equal. Conclusions: Understanding the relation between gender equality and health, which was found to depend on sex, life sphere, and inequality type, seems to require a combination of the hypotheses of convergence, stress and expansion.

Risks for Nonaffective Psychotic Disorder and Bipolar Disorder in Young People With Autism Spectrum Disorder: A Population-Based Study

IMPORTANCE Whether individuals with autism spectrum disorder (ASD) are at increased risk for nonaffective psychotic disorder (NAPD) or bipolar disorder (BD) is unknown. OBJECTIVE To test whether the risks for NAPD and BD in individuals with ASD are increased and whether these risks are higher than those of their siblings not diagnosed as having ASD. DESIGN, SETTING, AND PARTICIPANTS We performed a nested case-control study of all individuals 17 years or younger who ever resided in Stockholm County, Sweden, from January 1, 2001, through December 31, 2011 (Stockholm Youth Cohort). We included cohort members ever diagnosed as having ASD (n = 9062) and their full siblings never diagnosed as having ASD. Each case was matched with 10 control individuals of the same sex born during the same month and year. Using Swedish registers, cases, siblings, and controls were followed up until December 31, 2011. By then, the oldest individuals had reached the age of 27 years. EXPOSURES Autism spectrum disorder, registered before age 16 or 28 years. We distinguished between ASD with and without intellectual disability (ID). MAIN OUTCOMES AND MEASURES We calculated odds ratios (ORs) for NAPD and BD adjusted for age, sex, population density of place of birth, personal or parental history of migration, hearing impairment, parental age, parental income, parental educational level, and parental history of psychiatric disorder. RESULTS The adjusted ORs for NAPD and BD for cases with non-ID ASD registered before age 16 years were 5.6 (95% CI, 3.3-8.5) and 5.8 (95% CI, 3.9-8.7), respectively; the adjusted ORs for cases with ID ASD were 3.5 (95% CI, 2.0-6.0) and 1.8 (95% CI, 0.8-4.1). The adjusted ORs for NAPD and BD in cases with non-ID ASD registered before age 28 years were 12.3 (95% CI, 9.5-15.9) and 8.5 (95% CI, 6.5-11.2), respectively; for cases with ID ASD, these ORs were 6.4 (95% CI, 4.2-9.8) and 2.0 (95% CI, 1.0-3.9), respectively. The ORs for NAPD and BD for the nonautistic full siblings of cases for whom ASD was registered before age 16 years, adjusted for hearing loss, were 1.8 (95% CI, 1.1-2.7) and 1.7 (95% CI, 1.1-2.6), respectively. CONCLUSIONS AND RELEVANCE A diagnosis of ASD is associated with a substantially increased risk for NAPD and BD. This finding contributes to our understanding of these disorders and has implications for the management of ASD.

The age- and sex-specific occurrence of bothersome neck pain in the general population--results from the Stockholm public health cohort.

BackgroundNeck pain is very common but the occurrence of bothersome neck pain is not well described. Therefore our objective was to report on the prevalence and incidence of, as well as the rate of recovery from, bothersome neck pain in men and women of different ages in the general population.MethodsWe used data from a recently conducted population-based cohort study, comprising 23,794 individuals in Stockholm County, Sweden. Study participants were surveyed with a self-administered questionnaire in 2002/2003 and 2007, and information on episodes of neck pain was gathered at baseline and at follow-up. We then measured bothersome neck pain in 2005 and 2006 retrospectively in 2007 using the follow-up questionnaire.ResultsThe one-year prevalence of bothersome neck pain for at least seven consecutive days was 25% (95% confidence interval (CI): 24–25) among women and 16% (95% CI: 15–16) among men, peaking in individuals aged 30–59 years. The one-year incidence proportion of bothersome neck pain was 7% (95% CI: 6–7) among women, and 4% (95% CI: 4–5) among men. Women recovered more infrequently than men. The one-year incidence proportion of recovery (of at least one year duration) was 11% (95% CI: 10–12) among women and 14% (95% CI: 12–16) among men.ConclusionBothersome neck pain is most common in middle-aged individuals. Women are more likely than men to have and to develop bothersome neck pain, and less likely to recover from such pain. Younger men and women have a higher incidence, but recover more often from bothersome neck pain than older individuals.

Associations of Parental Depression With Child School Performance at Age 16 Years in Sweden

IMPORTANCE Depression is a common cause of morbidity and disability worldwide. Parental depression is associated with early-life child neurodevelopmental, behavioral, emotional, mental, and social problems. More studies are needed to explore the link between parental depression and long-term child outcomes. OBJECTIVE To examine the associations of parental depression with child school performance at the end of compulsory education (approximately age 16 years). DESIGN, SETTING, AND PARTICIPANTS Parental depression diagnoses (based on the International Classification of Diseases, Eighth Revision [ICD-8], International Classification of Diseases, Ninth Revision [ICD-9], and the International Statistical Classification of Diseases, 10th Revision [ICD-10]) in inpatient records from 1969 onward, outpatient records beginning in 2001, and school grades at the end of compulsory education were collected for all children born from 1984 to 1994 in Sweden. The final analytic sample size was 1,124,162 biological children. We examined the associations of parental depression during different periods (before birth, after birth, and during child ages 1-5, 6-10, and 11-16 years, as well as any time before the childs final year of compulsory schooling) with the final school grades. Linear regression models adjusted for various child and parent characteristics. The dates of the analysis were January to November 2015. MAIN OUTCOME AND MEASURE Decile of school grades at the end of compulsory education (range, 1-10, with 1 being the lowest and 10 being the highest). RESULTS The study cohort comprised 1,124,162 children, of whom 48.9% were female. Maternal depression and paternal depression at any time before the final compulsory school year were associated with worse school performance. After covariate adjustment, these associations decreased to -0.45 (95% CI, -0.48 to -0.42) and -0.40 (-0.43 to -0.37) lower deciles, respectively. These effect sizes are similarly as large as the observed difference in school performance between the lowest and highest quintiles of family income but approximately one-third of the observed difference between maternal education of 9 or less vs more than 12 years. Both maternal depression and paternal depression at different periods (before birth, after birth, and during child ages 1-5, 6-10, and 11-16 years) generally were associated with worse school performance. Child sex modified the associations of maternal depression with school performance such that maternal depression had a larger negative influence on child school performance for girls compared with boys. CONCLUSIONS AND RELEVANCE Diagnoses of parental depression throughout a childs life were associated with worse school performance at age 16 years. Our results suggest that diagnoses of parental depression may have a far-reaching effect on an important aspect of child development, with implications for future life course outcomes.

Exposure-dependent misclassification of exposure in interaction analyses.

The objectives of this paper are to analyze the consequences of exposure misclassification on effect estimates in interaction analysis, and to develop a mathematical equation for the potentially biased estimate. The main point is to identify situations in which misclassification of the first exposure, dependent on the second exposure but independent on outcome status, leads to overestimation or underestimation of the interaction effect. We show that misclassification theoretically can cause overestimation of the interaction effect. Nevertheless, because the categories that yield overestimation due to misclassification are fewer than the categories that yield underestimation, and misclassification in reality mostly is multidimensional (more than one category are biased simultaneously), it is more likely that the effect of misclassification is underestimation rather than overestimation. Misclassification in the categories that lead to overestimation is compensated by misclassification in the categories that lead to underestimation. The magnitude of the biased estimate depends on the prevalences of the misclassified exposure, stratified for the second exposure and the outcome-the lower the prevalence, the smaller the bias.