P6231Iron status and risk of cardio-metabolic diseases in European adults: a Mendelian randomization study

Background

Observational studies have reported conflicting results about the associations of iron status with risk of cardio-metabolic diseases but such studies are constrained by confounding and reverse causality.

Purpose

To assess the causal relevance of iron status biomarkers (transferrin, serum iron, and ferritin) for risk of coronary artery diseases (CAD), ischaemic stroke (IS), and type 2 diabetes (T2D), using Mendelian randomization (MR).

Methods

Effect size estimates for genetic variants associated with iron status biomarkers were obtained from the Genetics of Iron Status consortium (transferrin saturation, serum iron, and ferritin: n=48,972). The corresponding effects of these variants on the risk of CAD, IS and T2D were obtained from a meta-analysis of unrelated participants of European ancestry in the UK Biobank (UKB), together with previously recruited participants in CARDIOGRAMplusC4D (total n=90,377 CAD cases), MEGASTROKE (total n=43,381 IS cases) and DIAGRAM (total n=74,124 T2D cases), respectively. The main analysis used a two-sample inverse-variance weighted MR, while the sensitivity analyses used weighted-median, weighted-mode, MR-PRESSO, and MR-Egger approaches.

Results

MR analysis demonstrated significant inverse association of each of the three genetically-instrumented iron status biomarker with risk of CAD (transferrin saturation OR=0.96 [95% CI: 0.92–0.99], p=0.02; serum iron OR=0.93 [0.89–0.97], p=0.001; and ferritin OR=0.86 (0.79–0.94), p=0.001, per 1 SD higher level). In contrast, these iron status biomarkers showed positive associations with risk of T2D (transferrin saturation OR=1.06 [1.01–1.11], p=0.01; serum iron OR=1.06 [0.99–1.13], p=0.07; and ferritin OR=1.12 [0.99–1.26], p=0.06, per 1 SD higher level). There was positive, but non-significant, association of IS with each of the iron status biomarker analysed. Sensitivity analyses using several different MR approaches yielded concordant results.

Conclusions

Among European adults, iron status appeared to have causal associations, but in opposite directions, with the risk of CHD and T2D. Our findings highlight the need for caution about strategies for advocating iron supplementation in individuals with normal haemoglobin levels for prevention of CAD.

Acknowledgement/Funding

British Heart Found, Medical Research Council, Wellcome Trust, NIHR Biomedical Research Centre, Oxford

Cesarean delivery to prevent anal incontinence: a systematic review and meta-analysis

BACKGROUND

Cesarean delivery (CD), is increasingly recommended as a mode of delivery that prevents the anal incontinence (AI) that arises in some women after vaginal delivery (VD). The assessment of the efficacy of CD in this regard was the subject of this systematic review.

METHODS

Searches were conducted in Medline, EMBASE and the Cochrane Library. Both randomized (RCTs) and non-randomized trials (NRTs) comparing the risk of sustained fecal and/or flatus incontinence after VD or CD were sought from 1966 to 1 January, 2019. Studies were eligible if they assessed AI more than 6 months after birth, and had statistical adjustment for at least one of the three major confounders for AI: age, maternal weight or parity. In addition, each study was required to contain more than 250 participants, more than 50 CDs and more than 25 cases of AI. Data after screening and selection were abstracted and entered into Revman for meta-analysis. Analyses were done for combined fecal and flatus incontinence (comAI), fecal incontinence (FI), gas incontinence (GI), CD before or during labor, time trend of incontinence after delivery, assessment of both statistical and clinical heterogeneity, parity and late incident AI.

RESULTS

Out of the 2526 titles and abstracts found, 24 eligible studies were analyzed, 23 NRTs and one RCT. These included women with 29,597 VDs and women with 6821 CDs. Among the primary outcomes, VD was found not to be a significant predictor of postpartum comAI compared to CD in 6 studies, incorporating 18,951 deliveries (OR = 0.74; 0.54-1.02). VD was also not a significant predictor of FI in 14 studies, incorporating 29,367 deliveries, (OR = 0.89; 0.76-1.05). VD was not a significant predictor of GI in six studies, incorporating 6724 deliveries (OR = 0.96; 0.79-1.18). The strength of the grading of recommendations, assessment, development and evaluations (GRADE) evidence for each of these was low for comAI and moderate for FI and GI (upgrade for lack of expected effect). Time trend FI showed incontinence at 3 months often resolved at 1 year. Other secondary analyses assessing parity, delayed incidence of FI, clinical and statistical heterogeneity, spontaneous VD only, late risk of incidence of AI, and CD in or prior to labor all had similar results as in the primary outcomes.

CONCLUSIONS

There are three components of pelvic floor dysfunction that are thought to be caused by VD and hopefully prevented by CD: AI, urinary incontinence and pelvic floor prolapse. Of these, AI was not found to be reliably prevented by CD in this review.