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BACKGROUND:“Obesity paradox” refers to an association between obesity and reduced mortality (contrary to an expected increased mortality). A common explanation is collider stratification biasunmeasured confounding induced by selection bias. Here, we test this supposition through a realistic generative model. METHODS:We quantify the collider stratification bias in a selected population using counterfactual causal analysis. We illustrate the bias for a range of scenarios, describing associations between exposure (obesity), outcome (mortality), mediator (in this example, diabetes) and an unmeasured confounder. RESULTS:Collider stratification leads to biased estimation of the causal effect of exposure on outcome. However, the bias is small relative to the causal relationships between the variables. CONCLUSIONS:Collider bias can be a partial explanation of the obesity paradox, but unlikely to be the main explanation for a reverse direction of an association to a true causal relationship. Alternative explanations of the obesity paradox should be explored. See Video Abstract at http://links.lww.com/EDE/B51.

Abstract Introduction: Body mass index (BMI) is often elevated at type 2 diabetes (T2D) diagnosis. Using latent class trajectory modelling (LCTM) of BMI, we examined whether weight loss after diagnosis influenced cancer incidence and all-cause mortality. Methods: From 1995 to 2010, we identified 7,708 patients with T2D from the Salford Integrated Record database (UK) and linked to the cancer registry for information on obesity-related cancer (ORC), non-ORC; and all-cause mortality. Repeated BMIs were used to construct sex-specific latent class trajectories. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox regression models. Results: Four sex-specific BMI classes were identified; stable-overweight, stable-obese, obese-slightly-decreasing, and obese-steeply-decreasing; comprising 41%, 45%, 13%, and 1% of women, and 45%, 37%, 17%, and 1% of men, respectively. In women, the stable-obese class had similar ORC risks as the obese-slightly-decreasing class, whereas the stable-overweight class had lower risks. In men, the obese-slightly-decreasing class had higher risks of ORC (HR = 1.86, 95% CI: 1.05–3.32) than the stable-obese class, while the stable-overweight class had similar risks No associations were observed for non-ORC. Compared to the stable-obese class, women (HR = 1.60, 95% CI: 0.99–2.58) and men (HR = 2.37, 95% CI: 1.66–3.39) in the obese-slightly-decreasing class had elevated mortality. No associations were observed for the stable-overweight classes. Conclusion: Patients who lost weight after T2D diagnosis had higher risks for ORC (in men) and higher all-cause mortality (both genders) than patients with stable obesity.

Background The effect of ethnicity on the prevalence and management of hypertension and associated chronic kidney (CKD) disease in the UK is unknown. Methods We performed a cross sectional study of 49,203 adults with hypertension to establish the prevalence and management of hypertension and associated CKD by ethnicity. Routinely collected data from general practice hypertension registers in 148 practices in London between 1/1/07 and 31/3/08 were analysed. Results The crude prevalence of hypertension was 9.5%, and by ethnicity was 8.2% for White, 11.3% for South Asian and 11.1% for Black groups. The prevalence of CKD stages 3-5 among those with hypertension was 22%. Stage 3 CKD was less prevalent in South Asian groups (OR 0.77, 95% CI 0.67 - 0.88) compared to Whites (reference population) with Black groups having similar rates to Whites. The prevalence of severe CKD (stages 4-5) was higher in the South Asian group (OR 1.53, 95% CI 1.17 - 2.0) compared to Whites, but did not differ between Black and White groups. In the whole hypertension cohort, achievement of target blood pressure (< 140/90 mmHg) was better in South Asian (OR 1.43, 95% CI 1.28 - 1.60) and worse in Black groups (OR 0.79, 95% CI 0.74 - 0.84) compared to White patients. Hypertensive medication was prescribed unequally among ethnic groups for any degree of blood pressure control. Conclusions Significant variations exist in the prevalence of hypertension and associated CKD and its management between the major ethnic groups. Among those with CKD less than 50% were treated to a target BP of ≤ 130/80 mmHg. Rates of ACE-I/ARB prescribing for those with CKD were less than optimal, with the lowest rates (58.5%) among Black groups.

BackgroundThere is good evidence that confirms the importance of familial emotional support in adolescence on health across the life course and may protect from other disadvantages experienced during adolescence. This mixed methods study explores these enablers and barriers for families providing emotional support within Bradford, a young, multi-ethnic urban area with high deprivation.MethodsNine appreciative inquiry community workshops with parents and young people across Bradford; 39 in-depth interviews with parents and young people aged 12–16 (20 families) in the Born in Bradford (BiB) cohort and a cross-sectional analysis of the BiB Age of Wonder survey, completed by 3495 people aged 12–15 in 2022/23. Workshops used a participatory Ketso kit to gather responses. Interview transcripts were analysed thematically. We used ordinal logistic regression to test for association between emotional support (ES) and participant characteristics in cross-sectional survey data. Integration of the analysis from all data points occurred over a number of meetings between the research team and an external steering group.ResultsYoung people were facing a range of adverse emotional experiences and needed parental support. Cross-sectional analysis showed 54% of girls and 72.6% of boys reported high levels of ES (ordinal logistic regression boys were less likely to report lower ES compared to girls [OR 0.43, 95% CI 0.37–0.50]). In the year groups there was a trend for worsening emotional support in each year as children age. The workshops and interviews found that parental availability was a key enabler of emotional support. A key barrier to parental availability was their working patterns, including shift work, inflexible hours, multiple jobs and working away from the home. Better parental support was enabled by family activities such as daily mealtimes, days out and holidays but also passive, unstructured time as well as living nearby to (or sometimes with) extended family.ConclusionIf parents are less available their relationships with their children can be more distant and less supportive. This risks the creation of further inequalities for young people growing up in low-income households, where availability is more keenly tied to financial insecurity. The workshops and interviews work found mitigations to this, including the support of nearby family members and making the most of passive time together. Governments and employers need to recognise the continued importance of flexible working for parents as their children reach adolescence, as well as other contributors to job quality such as pay and working hours.

For some years, researchers working with primary care databases, such as the UK Clinical Practice Research Datalink (CPRD), have advocated linkage with other datasets speculating that this will enhance classification of exposures and outcomes. The article from McDonald et al. [1], focusing on CPRD, provides an updated review of studies offering empirical evidence to support the above advocacy. This is clearly illustrated with the example of classifying incident cancer.