ADuLT: An efficient and robust time-to-event GWAS.

Proportional hazards models have been proposed to analyse time-to-event phenotypes in genome-wide association studies (GWAS). However, little is known about the ability of proportional hazards models to identify genetic associations under different generative models and when ascertainment is present. Here we propose the age-dependent liability threshold (ADuLT) model as an alternative to a Cox regression based GWAS, here represented by SPACox. We compare ADuLT, SPACox, and standard case-control GWAS in simulations under two generative models and with varying degrees of ascertainment as well as in the iPSYCH cohort. We find Cox regression GWAS to be underpowered when cases are strongly ascertained (cases are oversampled by a factor 5), regardless of the generative model used. ADuLT is robust to ascertainment in all simulated scenarios. Then, we analyse four psychiatric disorders in iPSYCH, ADHD, Autism, Depression, and Schizophrenia, with a strong case-ascertainment. Across these psychiatric disorders, ADuLT identifies 20 independent genome-wide significant associations, case-control GWAS finds 17, and SPACox finds 8, which is consistent with simulation results. As more genetic data are being linked to electronic health records, robust GWAS methods that can make use of age-of-onset information will help increase power in analyses for common health outcomes.

The course of thyroid nodules and thyroid volume over a time period of up to 10 years: a longitudinal analysis of a population-based cohort.

OBJECTIVE: Thyroid disorders are common. Information on the long-term progression of morphologic disorders is scarce. The aim of this study was to describe the course of thyroid nodules and volume over a period of up to 10 years. DESIGN AND METHODS: Data from the population-based Study of Health in Pomerania were used for longitudinal analysis of 10 years, on average. Billing data from the Association of Statutory Health Insurance Physicians were matched to the data to exclude participants with thyroid surgery, radioiodine therapy and thyroid carcinoma. Changes in the number and size of thyroid nodules and thyroid volume were observed using ultrasound. RESULTS: A total of 1270 participants were included (53% female, median age at baseline 51 years). The proportion of subjects with at least one thyroid nodule increased from 34.9 to 47.5% after 10 years. The majority of participants had an unchanged or reduced number of nodules. About one-quarter had at least one nodule of size ≥ 1 cm. The proportion of participants with goitre increased from 35 to 37% after 10 years. Nevertheless, individual thyroid volume increased by < 1 mL (95% CI: 0.38-3.66) after adjusting for age and BMI irrespective of thyroid medication. CONCLUSION: Thyroid nodules and goitre are common. After 10 years, the number of nodules did not increase in about 70% of people. This proportion did not differ substantially when excluding people with thyroid medication. Thyroid volume increased slightly over the follow-up period. These changes do not seem clinically relevant. Our results support a more restrictive approach regarding follow-up diagnostics in asymptomatic patients with thyroid nodules or minimally enlarged thyroid.