How to Ensure Inclusivity in Large-Scale General Population Cohort Studies?:Lessons Learned with Regard to Including and Assessing Sex, Gender, and Sexual Orientation

Despite recent advances in the measurement of sex, gender, and sexual orientation in large-scale cohort studies, the three concepts are still gaining relatively little attention, may be mistakenly equated, or non-informatively operationalized. The resulting imprecise or lacking information hereon in studies is problematic, as sex, gender, and sexual orientation are important health-related factors. Omission of these concepts from general population cohort studies might dismiss participants’ identity and experiences and pushes research on sexual or gender minority populations toward purposive sampling, potentially introducing selection bias. It also reinforces the unintentional notion of irrelevance of these concepts to health research, ultimately disadvantaging sexual and gender minority populations. Similarly, a lack of uniform measures on sex, gender, and sexual orientation hampers multi-cohort studies in which data from multiple studies are combined, facilitating increased statistical power. This paper discusses the encountered pitfalls and lessons learned on including and assessing sex, gender, and sexual orientation in large-scale general population cohort studies, exemplified by the Dutch Lifelines Cohort Study. Additionally, we propose hands-on strategies on how to operationalize these concepts in an inclusive manner that is useful for large-scale general population cohort studies

The association of sex, age and FKBP5 genotype with common somatic symptoms:A replication study in the lifelines cohort study

OBJECTIVE: Our aim was to replicate a recent study that reported an association between the rs9470080 CC-genotype and common somatic symptoms in women, but not in men. Additionally, we quantified the genetic contribution to phenotypic variation in common somatic symptom levels. METHODS: We used data from the Lifelines Cohort Study, including 28,299 participants (60.0% female; 44.2% CC-genotype; mean age 42.9 (14.2) years). Common somatic symptoms were measured with the SCL-90 SOM subscale. To assess the association between the rs9470080 genotype and SCL-90 SOM scores we applied similar analyses as the original study, including independent t-tests, two-way ANOVAs and a mixed ANOVA. To estimate the proportion of phenotypic variance in SCL-90 SOM scores explained by single nucleotide polymorphisms (SNPs), we used a genomic-relatedness-based restricted maximum-likelihood method. RESULTS: We could not replicate the original study's findings. We found no association between the rs9470080 genotype and common somatic symptom levels in either female or male participants (F(1, 8775) = 1.07, p = 0.30 and F(1,13,903) = 0.01, p = 0.93, respectively). Genome-wide heritability analyses show that 12.1% (p = 2.1e-08) of the phenotypic variance in common somatic symptom levels in Lifelines can be explained by SNPs. The genetic contribution to common somatic symptom levels was higher in male participants (SNP-h2 = 20.5%; p = 9.1e-08) than in female participants (SNP-h2 = 12.0%, p = 2.8e-05). CONCLUSION: Our findings of significant SNP-h2 and the sex-specific differences herein, does warrant further sex-stratified research of individual genetic variants associated with common somatic symptoms. Preferably, further research should be performed within the analytic framework of a genome-wide association study

Stigma perceived by patients with functional somatic syndromes and its effect on health outcomes - A systematic review

BACKGROUND: Patients with functional somatic syndromes (FSS) experience stigma which arguably affects their health. AIM: To determine the presence of perceived stigma and its effects on physical and mental health in patients with FSS compared to patients with comparable explained conditions. METHODS: A comprehensive search of PubMed, Embase, PsycINFO, CINAHL and Cochrane Library was performed to select studies focusing on stigma perceived by patients with irritable bowel syndrome (IBS), fibromyalgia (FM) or chronic fatigue syndrome (CFS), comparing these patients to patients with comparable but explained conditions. RESULTS: We identified 1931 studies after duplicate removal. After screening we included eight studies: one study about all three FSS, one about IBS, five about FM and one about CFS. We found that patients with IBS did not consistently experience higher levels of stigma than those with a comparable explained condition. Patients with CFS and FM experienced higher levels of stigma compared to patients with comparable explained conditions. All studies showed a correlation between stigma and negative health outcomes. DISCUSSION: Patients with FSS experience stigma and negative health outcomes. However, experiencing stigma is not restricted to patients with FSS, as many patients with explained health conditions also experience stigma. Whether stigma has more negative health consequences in patients with FSS compared to patients with explained health conditions remains unclear and should be assessed in future research

Female sex and femininity independently associate with common somatic symptom trajectories

BACKGROUND: Multiple predictors have been associated with persistent somatic symptoms. However, previous studies problematically defined the persistence of symptoms, conflated participants' sex and gender, and focused on patient populations. Therefore, we studied associations between predictors, especially sex and gender, and longitudinal patterns of somatic symptoms in the general adult population. We also assessed whether predictors for persisting symptoms differ between sexes. METHOD: To identify developmental trajectories of somatic symptoms, assessed by the SCL-90 SOM, we used latent class trajectory modeling in the Dutch Lifelines Cohort Study [N = 150 494; 58.6% female; median time to follow-up: 46.0 (min-max: 22.0-123.0) months]. To identify predictors of trajectories, we applied multiple logistic regression analyses. Predictors were measured by surveys at baseline and a composite gender index was previously developed. RESULTS: A five-class linear LCGA model fitted the data best: 93.7% of the population had a stable symptom trajectory, whereas 1.5% and 4.8% of the population had a consistently increasing or decreasing symptom trajectory, respectively. Female sex predicted severe, stable symptom severity (OR 1.74, 95% CI 1.36-2.22), but not increasing symptom severity (OR 1.15, 95% CI 0.99-1.40). Femininity was protective hereof (OR 0.60, 95% CI 0.44-0.82 and OR 0.66, 95% CI 0.51-0.85, respectively). Merely a few predictors of symptom severity, for instance hours of paid employment and physical functioning, differed in strength between sexes. Yet, effect sizes were small. CONCLUSION: Female sex and femininity predict symptom trajectories. No large sex differences in the strength of additional predictors were found, thus it may not be clinically useful to distinguish between predictors specific to male or female patients of persistent somatic symptoms