Acoustofluidic, label-free separation and simultaneous concentration of rare tumor cells from white blood cells

Enrichment of rare cells from peripheral blood has emerged as a means to enable noninvasive diagnostics and development of personalized drugs, commonly associated with a prerequisite to concentrate the enriched rare cell population prior to molecular analysis or culture. However, common concentration by centrifugation has important limitations when processing low cell numbers. Here, we report on an integrated acoustophoresis-based rare cell enrichment system combined with integrated concentration. Polystyrene 7 μm microparticles could be separated from 5 μm particles with a recovery of 99.3 ± 0.3% at a contamination of 0.1 ± 0.03%, with an overall 25.7 ± 1.7-fold concentration of the recovered 7 μm particles. At a flow rate of 100 μL/min, breast cancer cells (MCF7) spiked into red blood cell-lysed human blood were separated with an efficiency of 91.8 ± 1.0% with a contamination of 0.6 ± 0.1% from white blood cells with a 23.8 ± 1.3-fold concentration of cancer cells. The recovery of prostate cancer cells (DU145) spiked into whole blood was 84.1 ± 2.1% with 0.2 ± 0.04% contamination of white blood cells with a 9.6 ± 0.4-fold concentration of cancer cells. This simultaneous on-chip separation and concentration shows feasibility of future acoustofluidic systems for rapid label-free enrichment and molecular characterization of circulating tumor cells using peripheral venous blood in clinical practice.

Do eating disorders in parents predict eating disorders in children? Evidence from a Swedish cohort

OBJECTIVE

We investigated whether parental eating disorders (ED) predict ED in children, using a large multigeneration register-based sample.

METHOD

We used a subset of the Stockholm Youth Cohort born 1984-1995 and resident in Stockholm County in 2001-2007 (N = 286,232), The exposure was a diagnosed eating disorder in a parent; the outcome was any eating disorder diagnosis in their offspring, given by a specialist clinician, or inferred from an appointment at a specialist eating disorder clinic. A final study sample of 158,697 (55.4%) had data on these variables and confounding factors and contributed a total of 886,241 person years to the analysis.

RESULTS

We found good evidence in support of the hypothesis that ED in either parent are independently associated with ED in their female children (HR 1.97 (95% CI: 1.17-3.33), P = 0.01) and that ED in mothers are independently associated with ED in their female children (HR 2.35 (95% CI: 1.39-3.97) P = 0.001). Numbers were too low to permit separate analysis of ED in parents and their male children.

CONCLUSION

Eating disorders in parents were associated with ED in children. This study adds to our knowledge about the intergenerational transmission of ED, which will help identify high-risk groups and brings about the possibility of targeted prevention.

Maternal body mass index during early pregnancy, gestational weight gain, and risk of autism spectrum disorders: Results from a Swedish total population and discordant sibling study

BACKGROUND

Prenatal environmental factors such as maternal adiposity may influence the risk of offspring autism spectrum disorders (ASD), though current evidence is inconsistent. The objective of this study was to assess the relationship of parental BMI and gestational weight gain (GWG) with risk of offspring ASD in a population-based cohort study using family-based study designs.

METHODS

The cohort was based in Stockholm County, Sweden, including 333,057 individuals born 1984-2007, of whom 6420 were diagnosed with an ASD. We evaluated maternal body mass index (BMI) at first antenatal visit, GWG and paternal BMI at the time of conscription into the Swedish military as exposures using general estimating equation (GEE) models with logit link.

RESULTS

At the population level, maternal overweight/obesity was associated with increased risk of offspring ASD [odds ratio (OR)25 ≤ BMI < 30 1.31, 95% confidence interval = 1.21-1.41; ORBMI ≥ 30 1.94, 1.72-2.17], as was paternal underweight (ORBMI < 18.5, 1.19, 1.06-1.33) and obesity (ORBMI ≥ 30 1.47, 1.12-1.92) in mutually adjusted models. However, in matched sibling analyses, the relationship between elevated maternal BMI and ASD risk was not apparent. GWG had a U-shaped association with offspring ASD at the population level (ORinsufficient 1.22, 1.07-1.40; ORexcessive 1.23, 1.08-1.40). Matched sibling analyses were suggestive of elevated risk with excessive GWG (ORinsufficient 1.12, 0.68-1.84; ORexcessive 1.48, 0.93-2.38).

CONCLUSIONS

Whereas population-level results suggested that maternal BMI was associated with ASD, sibling analyses and paternal BMI analyses indicate that maternal BMI may also be a proxy marker for other familial risk factors. Evidence is stronger for a direct link between GWG and ASD risk.

Concurrent isolation of lymphocytes and granulocytes using prefocused free flow acoustophoresis

Microchip-based free flow acoustophoresis (FFA) in combination with two-dimensional cell prefocusing enables concurrent multiple target outlet fractionation of leukocytes into subpopulations (lymphocytes, monocytes, and granulocytes); we report on this method here. We also observed significantly increased accuracy in size-based fractionation of microbeads as compared to previously presented FFA multiple outlet systems. Fluorescence microscopy illustrates the importance of two-dimensional prefocusing where a sample mixture of 3, 7, and 10 μm beads are separated into well-confined particle streams and collected in their respective target outlets. Flow cytometry data for lymphocytes and granulocytes, respectively, in their corresponding outlets verify concurrent isolation of leukocyte subpopulations with high purity (95.2 ± 0.6% and 98.5 ± 0.7%) and high recovery (86.5 ± 10.9% and 68.4 ± 10.6%). A relatively low purity and high recovery of monocytes (25.2% ± 5.4% and 83.1 ± 4.3%) was obtained in the third target outlet. No subpopulation bias was observed. These data demonstrate an unprecedented separation of leukocyte subpopulations at flow rates of ∼100 μL/min and ∼1 M cells/mL sample concentrations, not previously reported in acoustofluidic systems. Two-dimensional prefocusing FFA with multiple target outlets is a viable alternative to current methods for particle fractionation and cell isolation, requiring a minimum of sample preparation and lowering analysis time and cost.

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.

Parental mental illness and eating disorders in offspring

OBJECTIVE

To investigate which parental mental illnesses are associated with eating disorders in their offspring.

METHOD

We used data from a record-linkage cohort study of 158,679 children aged 12-24 years at the end of follow-up, resident in Stockholm County from 2001 to 2007, to investigate whether different parental mental illnesses are risk factors for eating disorders in their offspring. The outcome measure was diagnosis of any eating disorder, either from an ICD or DSM-IV code, or inferred from an appointment at a specialist eating disorder clinic.

RESULTS

Mental illness in parents is a risk factor for eating disorders in female offspring (Adjusted Hazard Ratio (AHR) 1.57 (95% CI 1.42, 1.92), p < 0.0001). Risk of eating disorders is increased if there is a parental diagnosis of bipolar affective disorder (AHR 2.28 (95% CI 1.39, 3.72), p = 0.004), personality disorder (AHR 1.57 (95% CI 1.01, 2.44), p = 0.043) or anxiety/depression (AHR 1.57 (95% CI 1.32, 1.86), p < 0.0001). There is a lack of statistical evidence for an association with parental schizophrenia (AHR 1.41 (95% CI 0.96, 2.07), p = 0.08), and somatoform disorder (AHR 1.25 (95% CI 0.74, 2.13), p = 0.40). There is no support for a relationship between parental substance misuse and eating disorders in children (AHR 1.08 (95% CI 0.82, 1.43), p = 0.57).

DISCUSSION

Parental mental illness, specifically parental anxiety, depression, bipolar affective disorder, and personality disorders, are risk factors for eating disorders in their offspring.

Longitudinal analysis of lifestyle habits in relation to body mass index, onset of overweight and obesity: results from a large population-based cohort in Sweden

AIMS

It is currently unknown whether the prevalence of obesity is increasing or has levelled off in Sweden and other Westernised countries. Given the major importance of lifestyle habits on weight status, we aimed to explore associations of longitudinal changes in lifestyle habits with changes in body mass index (BMI), and the onset of overweight and obesity.

METHODS

Participants (aged 18-84 years at baseline) were included from the Stockholm Public Health Cohort 2002-2010 (n=23,108). Weight status was from self-reported height and weight. Investigated lifestyle habits were leisure-time physical activity, and fruit, alcohol and smoking habits. We estimated associations of stable, improving or worsening lifestyle habits with longitudinal changes in BMI and onset of overweight or obesity between 2002 and 2010.

RESULTS

Both men and women increased in weight during the eight years of follow-up. Incidence of obesity was lower in men who increased their leisure-time physical activity (Relative Risk [RR]=0.58, 95% confidence interval 0.42-0.81) than in inactive individuals; the same applied to women (RR=0.37, 0.25-0.54), and similar patterns were identified for overweight and BMI in both genders. Smoking cessation was associated with onset of obesity for men (RR=1.69, 1.15-2.50) and women (RR=1.99, 1.39-2.85). Stable low alcohol intake or decreasing alcohol intake and daily fruit intake was associated with less weight gain, but only in men.

CONCLUSIONS

Improving physical activity in both men and women, and alcohol habits and fruit intake in men, prevents excess weight gain among adult people in Sweden. Such an improvement might diminish weight gain after smoking cessation.

Testing Ødegaard's selective migration hypothesis: a longitudinal cohort study of risk factors for non-affective psychotic disorders among prospective emigrants

BACKGROUND

The selection hypothesis posits that the increased rates of psychosis observed among migrants are due to selective migration of people who are predisposed to develop the disorder. To test this hypothesis, we examined whether risk factors for psychosis are more prevalent among future emigrants.

METHOD

A cohort of 49,321 Swedish military conscripts was assessed at age 18 years on cannabis use, IQ, psychiatric diagnosis, social adjustment, history of trauma and urbanicity of place of upbringing. Through data linkage we examined whether these exposures predicted emigration out of Sweden. We also calculated the emigrants' hypothetical relative risk compared with non-emigrants for developing a non-affective psychotic disorder.

RESULTS

Low IQ [odds ratio (OR) 0.5, 95% confidence interval (95% CI) 0.3-0.9] and 'poor social adjustment' (OR 0.4, 95% CI 0.2-0.8) were significantly less prevalent among prospective emigrants, whereas a history of urban upbringing (OR 2.3, 95% CI 1.4-3.7) was significantly more common. Apart from a non-significant increase in cannabis use among emigrants (OR 1.6, 95% CI 0.8-3.1), there were no major group differences in any other risk factors. Compared to non-emigrants, hypothetical relative risks for developing non-affective psychotic disorder were 0.7 (95% CI 0.4-1.2) and 0.8 (95% CI 0.7-1.0), respectively, for emigrants narrowly and broadly defined.

CONCLUSIONS

This study adds to an increasing body of evidence opposing the selection hypothesis.

The influence of school in the development of eating disorders: a record-linkage study

BACKGROUND

Clinical impression is that rates of eating disorders vary between schools; we are not aware of any previous research on this topic. We aimed to investigate whether rates of eating disorders in 16-20-year-old girls vary between upper secondary schools, and to test the hypothesis that school characteristics are associated with rates of eating disorders, even after accounting for characteristics of individual students.

METHODS

This multilevel longitudinal study made use of record-linkage data from Stockholm County, Sweden. Participants were 55 824 Swedish-born girls completing secondary education in 2001-10 at 409 schools. Outcome was any diagnosed eating disorder at 16-20 years, as defined by an ICD (9 or 10) or DSM-IV code, or inferred from an appointment at a specialist eating disorder clinic. Multilevel modelling was used to separate individual and school level effects. The Stockholm Regional Ethical Review Board approved the study.

FINDINGS

A 4·4% variation in incidence of eating disorders between schools was seen; after taking individual risk factors into account variation between schools was 2·9% (95% CI 1·5-5·0). Schools with a higher proportions of girls than boys had an increased incidence of eating disorders: for each 10% increase in the proportion of girls at a school, the odds ratio for eating disorders was 1·07 (95% CI 1·01-1·13, p=0·017). For each 10% increase in the proportion of parents with post-secondary education, the odds ratio for eating disorders was 1·14 (1·09-1·19, p<0·0001).

INTERPRETATION

Our findings show that the contextual aspects of a school environment are associated with increased incidence of eating disorders. Incidence rates of eating disorders are higher in schools characterised by a high proportion of female students and of students with highly educated parents. To our knowledge, this is the first study to investigate whether rates of eating disorders vary between schools; however, use of registry data means that individuals who did not seek treatment would not have been studied.

FUNDING

HB was supported by a Wellcome Trust Institutional Strategic Support Fund (via the Elizabeth Blackwell Institute).

Maternal hospitalization with infection during pregnancy and risk of autism spectrum disorders

Animal models indicate that maternal infection during pregnancy can result in behavioral abnormalities and neuropathologies in offspring. We examined the association between maternal inpatient diagnosis with infection during pregnancy and risk of ASD in a Swedish nationwide register-based birth cohort born 1984-2007 with follow-up through 2011. In total, the sample consisted of 2,371,403 persons with 24,414 ASD cases. Infection during pregnancy was defined from ICD codes. In the sample, 903 mothers of ASD cases (3.7%) had an inpatient diagnosis of infection during pregnancy. Logistic regression models adjusted for a number of covariates yielded odds ratios indicating approximately a 30% increase in ASD risk associated with any inpatient diagnosis of infection. Timing of infection did not appear to influence risk in the total Swedish population, since elevated risk of ASD was associated with infection in all trimesters. In a subsample analysis, infections were associated with greater risk of ASD with intellectual disability than for ASD without intellectual disability. The present study adds to the growing body of evidence, encompassing both animal and human studies, that supports possible immune-mediated mechanisms underlying the etiology of ASD.

Hospital admission with infection during childhood and risk for psychotic illness--a population-based cohort study

A growing body of literature suggests that exposure to infections, particularly maternal infections, during pregnancy confers risk for later development of psychotic disorder. Though brain development proceeds throughout childhood and adolescence, the influence of infections during these ages on subsequent psychosis risk is insufficiently examined. The aim of this study was to investigate the potential association between infections during childhood and nonaffective psychoses in a large population-based birth cohort with follow up long enough to include peak incidence of nonaffective psychosis. We included all individuals born in Sweden between 1973 and 1985, (N = 1172879), with follow up on first time inpatient care with nonaffective psychosis from age 14 years until 2006, (N = 4638). Following adjustment for differences in sex, socioeconomic status, family history of psychosis, and hospital admissions involving noninfectious, nonpsychiatric care, we observed a small but statistically significant association between hospital admissions for infections, in general, throughout childhood (0-13 years) and a later diagnosis of nonaffective psychosis, hazard ratio (HR) = 1.10 (95% CI 1.03-1.18), and this association seemed to be driven by bacterial infection, HR = 1.23 (95% CI 1.08-1.40). Bacterial infections and central nervous system infections during preadolescence (10-13 years) conferred the strongest risk, HR 1.57 (95% CI 1.21-2.05) and HR 1.96 (95% CI 1.05-3.62), respectively. Although preadolescence appeared to be a vulnerable age period, and bacterial infection the most severe in relation to psychosis development, the present findings can also indicate an increased susceptibility to hospital admission for infections among children who will later develop nonaffective psychosis due to social or familial/genetic factors.

Abstract 3077: Label free prostate cancer cell isolation from blood by acoustic standing wave technology - acoustophoresis

There is intense search for disease biomarkers that can reliably detect lethal prostate cancer (PCa) at early stage, monitor response to treatment, detect disease recurrence, and predict survival. Enrichment, enumeration, and transcriptional profiling of rare circulating tumor cells (CTCs) can predict survival of patients with disseminated tumors, and may provide clinical benefit in predicting treatment responses of targeted therapies.

We exploit ultrasound radiation forces to enable label free diversion of cancer cells from nucleated blood cells in a temperature-controlled, microfluidic continuous flow system (acoustophoresis). A third generation, standing-wave ultrasound microchip (silicon/glass) incorporated a cell pre-alignment channel, and a microchannel with a trifurcated inlet and outlet. The system is driven by compressed air (500 mBar) to mitigate and minimize continuous flow-fluctuations and provide more reproducible and reliable discrimination of tumor cells from nucleated blood cells compared to previous syringe driven setups, and allow us to process clinically relevant sample volumes of blood (5-10 mL).

We fixed, spiked, and processed 50 or more PCa cells per mL in undiluted white blood cells (WBC) in the acoustic microchip. The separation system is very flexible and the ratio between cancer cell recovery and cell contamination can be tuned by changing the sample flow rates or the acoustic energy. A consistent and reproducible recovery of cancer cells above 90% with less than 0.4% contamination of WBC was provided using flow rates of 100 l/min. We also found that about 90% of the contaminating WBCs were granulocytes, whereas the vast majority of lymphocytes were reliably diverted. Our results were consistent using different PCa cell lines (DU145, LNCaP, PC3) along with the breast cancer cell line (MCF7).

The isolation of cancer cells by acoustophoresis is a label free method that consistently enables high recovery of cancer cells independent of the expression of surface antigens. This allows for separation of EpCAM negative populations of CTCs, mesenchymal cells along with cancer stem cells, which can be identified with subsequent qRT-PCR analysis. In acoustophoresis, cells are separated according to size, density and compressibility (dV/dp), where size is the major factor. Using non-fixed samples, we can separate viable from dead cells, since dead cells display significantly different acoustic properties to their live counterpart. Acoustophoresis is a gentle separation method and does not affect cell viability, allowing post isolation ex vivo cultivation of CTCs. This allows functional assays to test CTCs ability to form metastasis. It is therefore a promising method for future non-invasive molecular interrogation of metastatic cancers and the characterization of CTCs will relate CTCs to disease outcome and predict for sensitivity to treatment and match patient to drug response.

Citation Format: Cecilia Magnusson, Per Augustsson, Benedikta Haflidadottir, Andreas Lenshof, Yvonne Ceder, Thomas Laurell, Hans Lilja. Label free prostate cancer cell isolation from blood by acoustic standing wave technology - acoustophoresis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3077. doi:10.1158/1538-7445.AM2014-3077

The sex-specific interrelationship between spinal pain and psychological distress across time in the general population. Results from the Stockholm Public Health Study

BACKGROUND CONTEXT

Detailed knowledge about the interrelationship between neck pain, back pain, and psychological distress is important from a public health prospective, but missing because of lack of large population-based cohort studies.

PURPOSE

To assess and compare the sex-specific recovery rate of spinal pain and psychological distress as single and comorbid conditions, to describe the interrelationship between these conditions at the baseline (2002) and follow-up 5 years later, and to explore the questions of spinal pain as a risk factor for the onset of psychological distress and vice versa.

STUDY DESIGN

A prospective cohort study.

PATIENT SAMPLE

General population in Stockholm county aged 18 to 84 years, n=19,774.

OUTCOME MEASURES

Spinal pain (modified Nordic Pain Questionnaire) and psychological distress (General Health Questionnaire-12).

METHODS

A random sample of the population in Stockholm was approached with postal questionnaires at the baseline and at follow-up.

RESULTS

Comorbidity of spinal pain and distress was twice as common among women (11%) than among men (4%) (relative risk=2.4, 95% confidence interval [CI]: 2.1-2.7). Women also more commonly had spinal pain without psychological distress (women, 20%; men, 14%) and vice versa (women, 15%; men, 12%). Comorbidity makes recovery less probable (women, 26%; men, 27%) than having single conditions of spinal pain (women, 41%; men, 44%) or psychological distress (women, 49%; men, 52%). No statistical significant sex differences were seen. Twenty-four percent of the women and 17% of the men with spinal pain without psychological distress at the baseline had psychological distress at follow-up. Corresponding figures for spinal pain among participants with psychological distress without spinal pain at the baseline were 24% and 20%. Spinal pain was a determinant of psychological distress (odds ratio [OR]=2.6, 95% CI: 2.3-2.9) and vice versa (OR=2.0, 95% CI: 1.8-2.2).

CONCLUSIONS

Spinal pain and psychological distress as comorbid and single conditions are common in the general population, especially among women. Comorbidity affects recovery negatively both in men and women. This study confirms the bidirectional association between spinal pain and psychological distress in the general population.

Prevalence and incidence of diabetes in Stockholm County 1990-2010

BACKGROUND

Diabetes is on the rise in the western world, but data from Scandinavia are inconsistent with indications of stable or even reverse trends. To shed new light on this issue, we investigated diabetes trends in Stockholm County 1990-2010, taking into account trends in risk factors and mortality.

METHODS

We used data from a large population-based quadrennial public health survey conducted between 1990 and 2010 in Stockholm County (∼ 2.1 million inhabitants), supplemented with data from national registers. The age-standardized prevalence and incidence rates of diabetes and related risk factors 1990-2010 were estimated in adult inhabitants. We also modelled the influence of potential risk factors on the diabetes trends and estimated the life time risk of diabetes.

RESULTS

The prevalence of diabetes was 4.6% (95% confidence interval (CI); 4.5-4.8%) in 2010 compared to 2.8% (95% CI; 2.3-3.5%) in 1990. Between 1990 and 2002 the prevalence rose annually by 3.8% (95% CI; 2.1-5.5). Incidence rates showed a similar pattern and rose by 3.0% (95% CI; 0.3-5.7%) annually 1990-2002. The rising incidence was mainly attributable to increasing prevalence of overweight/obesity, which rose by 46% during the observation period. In 2010, the lifetime risk of adult onset diabetes was 28% (95% CI; 26-31%) in men and 19% (95% CI; 17-21%) in women.

CONCLUSIONS

Diabetes rates have been increasing in Stockholm over the last decades, both in terms of incidence and prevalence, and this development is most likely the result of increasing overweight and obesity in the population.

Snus (Swedish smokeless tobacco) use and risk of stroke: pooled analyses of incidence and survival

BACKGROUND

Snus is a moist smokeless tobacco product with high nicotine content. Its use has a short-term effect on the cardiovascular system, but the relationship between snus use and stroke is unclear.

OBJECTIVE

The aim of this study was to assess the associations between use of snus and incidence of and survival after stroke, both overall and according to subtypes.

METHODS

Pooled analyses of eight Swedish prospective cohort studies were conducted, including 130 485 men who never smoked. We estimated hazard ratios (HRs) with 95% confidence intervals (CIs) of incidence and death after diagnosis using Cox proportional hazard regression models and case fatality and survival using logistic regression and Kaplan-Meier methods, respectively.

RESULTS

No associations were observed between the use of snus and the risk of overall stroke (HR 1.04, 95% CI 0.92-1.17) or of any of the stroke subtypes. The odds ratio (OR) of 28-day case fatality was 1.42 (95% CI 0.99-2.04) amongst users of snus who had experienced a stroke, and the HR of death during the follow-up period was 1.32 (95% CI 1.08-1.61).

CONCLUSION

Use of snus was not associated with the risk of stroke. Hence, nicotine is unlikely to contribute importantly to the pathophysiology of stroke. However, case fatality was increased in snus users, compared with nonusers, but further studies are needed to determine any possible causal mechanisms.

Exposure to maternal smoking during pregnancy as a risk factor for tobacco use in adult offspring

Nicotine from maternal smoking during pregnancy can cross the placental barrier, possibly resulting in fetal brain sensitization, as indicated by studies in which prenatal exposure to maternal smoking was associated with an increased risk of tobacco use among adolescent offspring. We investigated whether this association persists beyond adolescence by studying cigarette smoking and the use of snus (Swedish oral moist snuff) among 983 young adults from a prospective cohort study conducted in Stockholm, Sweden, between 2006 and 2010. Self-reported questionnaire data were linked with data from national population-based registers from 1983 onward. Maternal smoking during pregnancy was consistently associated with snus use in offspring (e.g., for lifetime daily snus use, adjusted odds ratio = 2.04, 95% confidence interval: 1.32, 3.16; for use of >3 cans of snus per week vs. less, odds ratio = 3.85, 95% confidence interval: 1.57, 10.15). No association was apparent with offspring's smoking, age at onset of tobacco use, or changes in use between 2006 and 2010. These findings indicate that prenatal exposure to maternal smoking is associated with regular and heavy nicotine intake from smokeless tobacco rather than from smoking. This should be further explored in epidemiologic studies that simultaneously address the roles of genetics and social environments.

In-utero exposure to maternal smoking is not linked to tobacco use in adulthood after controlling for genetic and family influences: a Swedish sibling study

Previous studies have linked maternal smoking during pregnancy with regular tobacco use in offspring, but findings are not consistent and confounding from genetic and environmental factors have not fully been taken into account. A comparison between siblings discordant for prenatal smoking exposure adjusts for confounding by shared familial (i.e., genetic and environmental) factors. We investigated the association between prenatal exposure to maternal smoking during pregnancy and the risk of regular smoking or snus (Swedish moist smokeless tobacco) use in young adult offspring, using a population based matched cohort study. The cohort consisted of 1,538 randomly sampled same-sex sibling pairs, discordant for maternal smoking during pregnancy, 19-27 years old, participating in a survey conducted in Sweden 2010-2011. Lifetime and current history of tobacco use was self-reported in the survey, and information about maternal smoking during pregnancy was retrieved from the Medical Birth Register. Conditional logistic regression and stratified Cox proportional hazards regression were used to calculate odds ratios, hazard ratios, and corresponding 95% confidence intervals. Analyses of exposure-discordant siblings did not reveal significant associations between prenatal exposure to maternal smoking and lifetime or current daily tobacco use, intensity of use, or time to onset of daily tobacco use. These findings suggest that the previously reported higher risks of tobacco use in offspring of mothers who smoked during pregnancy, compared with offspring of non-smoking mothers, were likely due to confounding from genetic or environmental factors.

School performance and the risk of suicide attempts in young adults: a longitudinal population-based study

BACKGROUND

Poor school performance is strongly associated with attempted suicide, but the mechanisms underlying this association are uncertain. We examined this relationship and the extent to which it is explained by (i) adult health behaviours and (ii) social conditions. Furthermore, we examined the potential modifying role of previous suicidal thoughts in the relationship.

METHOD

We conducted a longitudinal cohort study of 6146 individuals aged 18-33 years, recruited in 2002 and 2006 in Stockholm and resurveyed in 2007 and 2010 respectively. We estimated the risk of reported lifetime suicide attempts at follow-up among individuals without a history of suicide attempts at baseline and in relation to compulsory school-leaving grades, controlling for possible confounders and mediators.

RESULTS

There were 91 cases of self-reported suicide attempts during the follow-up (5-year incidence of 1.5%). ORs ranged from 3.35 [95% confidence interval (CI) 1.88-5.96] for those in the lowest grade quartile to 2.60 (95% CI 1.48-4.57) and 1.76 (95% CI 0.99-3.13) for those in the second and third quartiles respectively. The relationship between school performance and risk of suicide attempts did not differ by sex. Adult health behaviours and social conditions marginally attenuated, but did not explain, the relationship. The gradient varied with baseline history of suicidal thoughts, and was found only among individuals without such a history.

CONCLUSIONS

Poor school performance was found to predict suicide attempts among young adults without a history of suicidal thoughts. Adult health behaviours and social conditions did not explain this relationship. Instead, other factors linked with poor school performance, such as poor coping ability, may increase the risk of suicide attempts.

Severe bereavement stress during the prenatal and childhood periods and risk of psychosis in later life: population based cohort study

OBJECTIVE

To examine the risk of psychosis associated with severe bereavement stress during the antenatal and postnatal period, between conception to adolescence, and with different causes of death.

DESIGN

Population based cohort study.

SETTING

Swedish national registers including births between 1973 and 1985 and followed-up to 2006.

PARTICIPANTS

In a cohort of 1,045,336 Swedish births (1973-85), offspring born to mothers exposed to severe maternal bereavement stress six months before conception or during pregnancy, or exposed to loss of a close family member subsequently from birth to 13 years of age were followed until 2006. Admissions were identified by linkage to national patient registers.

MAIN OUTCOME MEASURES

Crude and adjusted odds ratios for all psychosis, non-affective psychosis, and affective psychosis.

RESULTS

Maternal bereavement stress occurring preconception or during the prenatal period was not associated with a significant excess risk of psychosis in offspring (adjusted odds ratio, preconception 1.24, 95% confidence interval 0.96 to 1.62; first trimester 0.95, 0.58 to 1.56; second trimester 0.79, 0.46 to 1.33; third trimester 1.14, 0.78 to 1.66). Risks increased modestly after exposure to the loss of a close family member from birth to adolescence for all psychoses (adjusted odds ratio 1.17, 1.04 to 1.32). The pattern of risk was generally similar for non-affective and affective psychosis. Thus estimates were higher after death in the nuclear compared with extended family but remained non-significant for prenatal exposure; the earlier the exposure to death in the nuclear family occurred in childhood (all psychoses: adjusted odds ratio, birth to 2.9 years 1.84, 1.41 to 2.41; 3-6.9 years 1.47, 1.16 to 1.85; 7-12.9 years 1.32, 1.10 to 1.58) and after suicide. Following suicide, risks were especially higher for affective psychosis (birth to 2.9 years 3.33, 2.00 to 5.56; 6.9 years 1.84, 1.04 to 3.25; 7-12.9 years 2.68, 1.84 to 3.92). Adjustment for key confounders attenuated but did not explain associations with risk.

CONCLUSIONS

Postnatal but not prenatal bereavement stress in mothers is associated with an increased risk of psychosis in offspring. Risks are especially high for affective psychosis after suicide in the nuclear family, an effect that is not explained by family psychiatric history. Future studies are needed to understand possible sources of risk and resilience so that structures can be put in place to support vulnerable children and their families.

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.

We are family--parents, siblings, and eating disorders in a prospective total-population study of 250,000 Swedish males and females

OBJECTIVE

We examined how parental characteristics and other aspects of family background were associated with the development of eating disorders (ED) in males and females.

METHOD

We used register data and record linkage to create the prospective, total-population study the Stockholm Youth Cohort. This cohort comprises all children and adolescents who were ever residents in Stockholm County between 2001 and 2007, plus their parents and siblings. Individuals born between 1984 and 1995 (N = 249, 884) were followed up for ED from age 12 to end of 2007. We used Cox regression modeling to investigate how ED incidence was associated with family socioeconomic position, parental age, and family composition.

RESULTS

In total, 3,251 cases of ED (2,971 females; 280 males) were recorded. Higher parental education independently predicted a higher rate of ED in females [e.g., adjusted hazard ratio (HR) 1.69 (95% CI: 1.42, 2.02) for degree-level vs. elementary-level maternal education], but not in males [HR 0.73 (95% CI: 0.42, 1.28), p < 0.001 for gender interaction]. In females, an increasing number of full-siblings was associated with lower rate of ED [e.g., fully adjusted HR 0.92 (95% CI: 0.88, 0.97) per sibling], whereas an increasing number of half-siblings was associated with a higher rate [HR 1.05 (95% CI: 1.01, 1.09) per sibling].

DISCUSSION

The effect of parental education on ED rate varies between males and females, whereas the effect of number of siblings varies according to whether they are full or half-siblings. A deeper understanding of these associations and their underlying mechanisms may provide etiological insights and inform the design of preventive interventions.

Hearing and speech impairment at age 4 and risk of later non-affective psychosis

BACKGROUND

Schizophrenia often becomes manifest in late adolescence and young adulthood but deviations in physical and behavioural development may already be present in childhood. We investigated the relationship between hearing impairment (measured with audiometry) and speech impairment (broadly defined) at age 4 years and adult risk of non-affective psychosis.

METHOD

We performed a population-based, case–control study in Sweden with 105 cases of schizophrenia or other non-affective psychoses and 213 controls matched for sex, date and place of birth. Information on hearing and speech impairment at age 4, along with potential confounding factors, was retrieved from Well Baby Clinic (WBC) records.

RESULTS

Hearing impairment [odds ratio (OR) 6.0, 95% confidence interval (CI) 1.6–23.2] and speech impairment (OR 2.6, 95% CI 1.4–4.9) at age 4 were associated with an increased risk of non-affective psychotic illness. These associations were mutually independent and not explained by parental psychiatric history, occupational class or obstetric complications.

CONCLUSIONS

These results support the hypothesis that psychosis has a developmental aspect with presentation of antecedent markers early in childhood, long before the disease becomes manifest. Our findings add to the growing evidence that early hearing impairment and speech impairment are risk indicators for later non-affective psychosis and possibly represent aetiological clues and potentially modifiable risk factors. Notably, speech impairment and language impairment are both detectable with inexpensive, easily accessible screening.