Hidradenitis suppurativa is associated with higher heart rate but not atrial fibrillation: A comparative cross-sectional study of 462 individuals with hidradenitis suppurativa in Denmark

Hidradenitis suppurativa (HS) is a chronic inflammatory dermatological disease with inflammatory mechanisms overlapping those of psoriasis, and both diseases have been associated with cardiovascular risk factors i.e. smoking and metabolic syndrome. Two studies have recently linked psoriasis with Atrial Fibrillation (AF). AF is the most frequently occurring cardiac arrhythmia in the general population and is typically accompanied by increased heart rate. Both AF and heart rate are linked with inflammation.The aim of the study was to investigate a potential association between HS and increased heart rate as well as AF.We performed a comparative cross-sectional study using digital measurements of heart rate and resting 12-lead electrocardiography (ECG) in combination with self-reported information when diagnosing AF.Our study comprised 32 individuals with HS from the hospital (the hospital HS group), 430 from the general population HS group (the population HS group), and 20,780 controls. Age and sex adjusted analysis demonstrated a significantly higher heart rate in the HS groups vs. controls (15% (range: 8-23%) higher for the hospital HS group and 4% (2-5%) higher for the population HS group). We found no association between HS and AF (P=0.1670). </p

Evaluating Random Forests for Survival Analysis Using Prediction Error Curves

Prediction error curves are increasingly used to assess and compare predictions in survival analysis. This article surveys the R package pec which provides a set of functions for efficient computation of prediction error curves. The software implements inverse probability of censoring weights to deal with right censored data and several variants of cross-validation to deal with the apparent error problem. In principle, all kinds of prediction models can be assessed, and the package readily supports most traditional regression modeling strategies, like Cox regression or additive hazard regression, as well as state of the art machine learning methods such as random forests, a nonparametric method which provides promising alternatives to traditional strategies in low and high-dimensional settings. We show how the functionality of pec can be extended to yet unsupported prediction models. As an example, we implement support for random forest prediction models based on the R packages randomSurvivalForest and party. Using data of the Copenhagen Stroke Study we use pec to compare random forests to a Cox regression model derived from stepwise variable selection

Negative confounding by essential fatty acids in methylmercury neurotoxicity associations

BACKGROUND: Methylmercury, a worldwide contaminant of fish and seafood, can cause adverse effects on the developing nervous system. However, long-chain n-3 polyunsaturated fatty acids in seafood provide beneficial effects on brain development. Negative confounding will likely result in underestimation of both mercury toxicity and nutrient benefits unless mutual adjustment is included in the analysis. METHODS: We examined these associations in 176 Faroese children, in whom prenatal methylmercury exposure was assessed from mercury concentrations in cord blood and maternal hair. The relative concentrations of fatty acids were determined in cord serum phospholipids. Neuropsychological performance in verbal, motor, attention, spatial, and memory functions was assessed at 7 years of age. Multiple regression and structural equation models (SEMs) were carried out to determine the confounder-adjusted associations with methylmercury exposure. RESULTS: A short delay recall (in percent change) in the California Verbal Learning Test (CVLT) was associated with a doubling of cord blood methylmercury (−18.9, 95% confidence interval [CI] = −36.3, −1.51). The association became stronger after the inclusion of fatty acid concentrations in the analysis (−22.0, 95% confidence interval [CI] = −39.4, −4.62). In structural equation models, poorer memory function (corresponding to a lower score in the learning trials and short delay recall in CVLT) was associated with a doubling of prenatal exposure to methylmercury after the inclusion of fatty acid concentrations in the analysis (−1.94, 95% CI = −3.39, −0.49). CONCLUSIONS: Associations between prenatal exposure to methylmercury and neurobehavioral deficits in memory function at school age were strengthened after fatty acid adjustment, thus suggesting that n-3 fatty acids need to be included in analysis of similar studies to avoid underestimation of the associations with methylmercury exposure