Towards non-conventional methods of designing register-based epidemiological studies: An application to pediatric research

Pneumonia in Infancy and Risk for Asthma: The Role of Familial Confounding and Pneumococcal Vaccination

BACKGROUND

Studies have reported an increased risk for asthma following lower respiratory tract infections, but few studies have specifically assessed this risk in children diagnosed with pneumonia in infancy. Furthermore, it is not fully understood whether this association is indicative of a causal relationship or if certain children have a predisposition for both diseases.

RESEARCH QUESTION

Are children diagnosed with pneumonia in infancy at increased risk for asthma, and what is the role of familial confounding and pneumococcal conjugate vaccine immunization on the association?

STUDY DESIGN AND METHODS

This study was a nationwide register-based cohort analysis of > 900,000 Swedish children to assess the association between pneumonia in infancy and prevalent asthma at 4 years. A secondary aim was to assess if the association has changed after the introduction of nationwide pneumococcal conjugate vaccine (PCV) immunization as this has led to a shift in pneumonia etiology. The study controlled for important confounders, including shared environmental and familial confounding, by using sibling analyses.

RESULTS

There was a strong association between pneumonia diagnosis in infancy and prevalent asthma at 4 years (adjusted OR, 3.38; 95% CI, 3.26-3.51), as well as in the full sibling analyses (adjusted OR, 2.81; 95% CI, 2.58-3.06). The risk for asthma following pneumonia diagnosis in infancy was slightly higher for those born in the PCV period compared with the pre-PCV period (adjusted OR, 3.80 [95% CI, 3.41-4.24] vs 3.28 [95% CI, 3.15-3.42]) when the proportion of viral pneumonia etiology was also higher (14.5% vs 10.7%, respectively) and the overall asthma prevalence was lower (5.3% vs 6.6%).

INTERPRETATION

Children diagnosed with pneumonia in infancy have a highly increased risk for prevalent asthma at 4 years, which might have implications for future asthma preventive measures and needs to be considered when assessing the morbidity that can be attributed to pneumonia.

Developments in the field of clinical allergy in 2018 through the eyes of Clinical and Experimental Allergy, Part II

In this article, we describe developments in the field of clinical allergy as described by Clinical and Experimental Allergy in 2018; epidemiology, asthma and rhinitis, clinical allergy and allergens are all covered.

Implementation of Advanced Methods for Reproductive Pharmacovigilance in Autism: A Meta-Analysis of the Effects of Prenatal Antidepressant Exposure

OBJECTIVE

Observational studies of prenatal antidepressant safety are hindered by methodological concerns, including susceptibility to surveillance bias. Some studies address potential bias by using alternative strategies to operationalize study comparison groups. In a meta-analysis of the association between prenatal antidepressant exposure and autism risk, the authors examined the utility of comparison group operationalization in reducing surveillance bias.

METHODS

A systematic search of multiple databases through August 2017 was conducted, selecting controlled observational studies of the association of prenatal antidepressant exposure with autism. Study quality was assessed using the Newcastle-Ottawa Scale. Random-effects meta-analysis produced summary effect measures with 95% confidence intervals stratified by comparator group composition, antidepressant class, and trimester of exposure.

RESULTS

Fourteen studies were included, with 13 reporting results using a population-based comparison group, five using a psychiatric control group, and four using a discordant-sibling control group. Eight of the 14 studies were rated poor because of inadequate control for prenatal depression and maternal ethnicity. Autism risk estimates after prenatal exposure to any antidepressant were decidedly different for population-based designs (hazard ratio=1.42, 95% CI=1.18, 1.70; odds ratio=1.58, 95% CI=1.25, 1.99) compared with psychiatric control (hazard ratio=1.14, 95% CI=0.84, 1.53; odds ratio=1.24, 95% CI=0.93, 1.66) and discordant-sibling (hazard ratio=0.97, 95% CI=0.68, 1.37; odds ratio=0.85, 95% CI=0.54, 1.35) designs. Findings for prenatal exposure to selective serotonin reuptake inhibitors were similar. Meta-regression of population-based studies demonstrated that despite statistical adjustment, ethnicity differences remained a significant source of study heterogeneity.

CONCLUSIONS

In this meta-analysis, neither psychiatric control nor discordant-sibling designs supported an association between prenatal antidepressant exposure and autism. Discordant-sibling designs effectively addressed surveillance bias in pharmacovigilance reports derived from national registries and other large databases.

Developments in the field of allergy in 2017 through the eyes of Clinical and Experimental Allergy

In this article, we described the development in the field of allergy as described by Clinical and Experimental Allergy in 2017. Experimental models of allergic disease, basic mechanisms, clinical mechanisms, allergens, asthma and rhinitis and clinical allergy are all covered.

Longitudinal depression or anxiety in mothers and offspring asthma: a Swedish population-based study

Background

Previous research has found that maternal stress during pregnancy increases the risk of offspring asthma. However, whether this association is consistent with a causal interpretation has never been tested. The objective is to determine whether there is a critical exposure period for maternal depression or anxiety on offspring asthma or whether cumulative exposure is most important, and to investigate evidence of confounding.

Methods

The study population included all children born in Sweden from July 2006 to December 2009 (n = 360 526). Information about childhood asthma, maternal depression or anxiety (diagnosis or medication) and covariates was obtained from the Swedish national health registers. The associations between exposure periods (pre-conception, pregnancy, postnatal or current) and childhood asthma were estimated using structured life course approach hypothesis testing. Paternal and cousin analyses were used to test for evidence of confounding from shared genes and environment.

Results

For childhood asthma, cumulative exposure best described the effect of exposure to maternal depression or anxiety up to a maximum of any two exposure periods [adjusted odds ratio 1.44, 95% confidence interval (CI) 1.38, 1.52]. The hypotheses of a critical period were not supported. The paternal and cousin analyses indicated minimal influence from familial confounding.

Conclusions

These findings support an association between cumulative exposure to maternal depression or anxiety and asthma development in offspring. This association is unique for maternal depression or anxiety and not due to familial confounding. The clinical implication is that effective psychological management of women with chronic distress may reduce offspring asthma risk.

Prenatal maternal psychosocial stress and offspring's asthma and allergic disease: A systematic review and meta-analysis

BACKGROUND

Prenatal maternal stress may influence offspring's atopic risk through sustained cortisol secretion resulting from activation of the hypothalamic-pituitary axis (HPA), leading to Th2-biased cell differentiation in the foetus. We undertook a systematic review and meta-analysis investigating the relationship between prenatal maternal psychosocial stress and risk of asthma and allergy in the offspring.

METHODS

We searched 11 electronic databases from 1960 to 2016, searched the grey literature and contacted experts in the field. Type of stress indicator included mood disorders, anxiety, exposure to violence, bereavement and socio-economic problems occurring during pregnancy, both objectively and subjectively measured. We included all possible asthma and IgE-mediated allergy outcomes. We conducted random-effects meta-analyses to synthesize the data.

RESULTS

We identified 9779 papers of which 30 studies (enrolling >6 million participants) satisfied inclusion criteria. The quality of 25 studies was moderate, 4 were strong, and one was weak. Maternal exposure to any type of stressors was associated with an increased risk of offspring atopic eczema/dermatitis (OR 1.34, 95% CI 1.22-1.47), allergic rhinitis (OR 1.30, 95% CI 1.04-1.62), wheeze (OR 1.34, 95% CI 1.16-1.54) and asthma (OR 1.15, 95% CI 1.04-1.27). Exposure to anxiety and depression had strongest effect compared to other stressors. Exposure during the third trimester had the greatest impact compared to first and second trimesters. The increased risk was stronger for early-onset and persistent than for late-onset wheeze. Bereavement of a child (HR 1.28, 95% CI 1.10-1.48) or a spouse (HR 1.40, 95% CI 1.03-1.90) increased the risk of offspring asthma.

CONCLUSIONS

Exposure to prenatal maternal psychosocial stress was associated with increased risk, albeit modestly, of asthma and allergy in the offspring. The pronounced risk during the third trimester may represent cumulative stress exposure throughout pregnancy rather than trimester-specific effect. Our findings may represent a causal effect or a result of inherent biases in studies, particularly residual confounding.