Case-Control Studies

Sexual Function and Depressive Symptoms in Young Women with Euthyroid Hashimoto's Thyroiditis Receiving Vitamin D, Selenomethionine and Myo-Inositol: A Pilot Study

Thyroid autoimmunity is associated with an increased risk of sexual dysfunction. The aim of this study was to compare sexual functioning and depressive symptoms in women with Hashimoto's thyroiditis receiving different treatments. The study included euthyroid women with autoimmune thyroiditis, untreated or receiving vitamin D, selenomethionine, or myo-inositol. Apart from measuring antibody titers and hormone levels, all participants completed questionnaires evaluating female sexual function (FSFI) and depressive symptoms (BDI-II). In untreated women, the overall FSFI scores and domain scores for desire, arousal, lubrication, and sexual satisfaction were lower than in women receiving vitamin D, selenomethionine, and myo-inositol. In the vitamin D-treated women, the total FSFI scores and scores for desire and arousal were higher than in women receiving the remaining micronutrients. The BDI-II score was lowest in the vitamin D-treated women and highest in the untreated patients with thyroiditis. Vitamin D-treated women were also characterized by lower antibody titers and higher testosterone levels than the women receiving the remaining micronutrients. There were no differences in sexual functioning and depressive symptoms between the selenomethionine- and myo-inositol-treated women. The study results suggest that although all antibody-lowering treatments are associated with better sexual functioning and well-being in young women with euthyroid autoimmune thyroiditis, the greatest benefits are observed in patients receiving vitamin D.

Mendelian randomization as a tool to gain insights into the mosaic causes of autoimmune diseases

Autoimmune diseases (ADs) are a broad range of disorders which are characterized by long-term inflammation and tissue damage arising from an immune response against one's own tissues. It is now widely accepted that the causes of ADs include environmental factors, genetic susceptibility and immune dysregulation. However, the exact etiology of ADs has not been fully elucidated to date. Because observational studies are plagued by confounding factors and reverse causality, no firm conclusions can be drawn about the etiology of ADs. Over the years, Mendelian randomization (MR) analysis has come into focus, offering unique perspectives and insights into the etiology of ADs and promising the discovery of potential therapeutic interventions. In MR analysis, genetic variation (alleles are randomly dispensed during meiosis, usually irrespective of environmental or lifestyle factors) is used instead of modifiable exposure to explore the link between exposure factors and disease or other outcomes. Therefore, MR analysis can provide a valuable method for exploring the causal relationship between different risk factors and ADs when its inherent assumptions and limitations are fully considered. This review summarized the recent findings of MR in major ADs, including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), multiple sclerosis (MS), and type 1 diabetes mellitus (T1DM), focused on the effects of different risk factors on ADs risks. In addition, we also discussed the opportunities and challenges of MR methods in ADs research.

Reflection on modern methods: risk ratio regression-simple concept yet complex computation

The risk ratio (RR) is the ratio of the outcome among the exposed to risk of the outcome among the unexposed. This is a simple concept, which makes one wonder why it has not gained the same popularity as the odds ratio. Using logistic regression to estimate the odds ratio is quite common in epidemiology and interpreting the odds ratio as a risk ratio, under the assumption that the outcome is rare, is also common. On one hand, estimating the odds ratio is simple but interpreting it is hard. On the other, estimating the risk ratio is challenging but its interpretation is straightforward. Issues with estimating risk ratio still remain after four decades. These issues include convergence of the algorithm, the choice of regression specification (e.g. log-binomial, Poisson) and many more. Various new computational methods are available which help overcome the issue of convergence and provide doubly robust estimates of RR.

Estimating risk ratio from any standard epidemiological design by doubling the cases

Background

Despite the ease of interpretation and communication of a risk ratio (RR), and several other advantages in specific settings, the odds ratio (OR) is more commonly reported in epidemiological and clinical research. This is due to the familiarity of the logistic regression model for estimating adjusted ORs from data gathered in a cross-sectional, cohort or case-control design. The preservation of the OR (but not RR) in case-control samples has contributed to the perception that it is the only valid measure of relative risk from case-control samples. For cohort or cross-sectional data, a method known as ‘doubling-the-cases’ provides valid estimates of RR and an expression for a robust standard error has been derived, but is not available in statistical software packages.

Methods

In this paper, we first describe the doubling-of-cases approach in the cohort setting and then extend its application to case-control studies by incorporating sampling weights and deriving an expression for a robust standard error. The performance of the estimator is evaluated using simulated data, and its application illustrated in a study of neonatal jaundice. We provide an R package that implements the method for any standard design.

Results

Our work illustrates that the doubling-of-cases approach for estimating an adjusted RR from cross-sectional or cohort data can also yield valid RR estimates from case-control data. The approach is straightforward to apply, involving simple modification of the data followed by logistic regression analysis. The method performed well for case-control data from simulated cohorts with a range of prevalence rates. In the application to neonatal jaundice, the RR estimates were similar to those from relative risk regression, whereas the OR from naive logistic regression overestimated the RR despite the low prevalence of the outcome.

Conclusions

By providing an R package that estimates an adjusted RR from cohort, cross-sectional or case-control studies, we have enabled the method to be easily implemented with familiar software, so that investigators are not limited to reporting an OR and can examine the RR when it is of interest.

Permanent childhood hearing impairment in infants admitted to the neonatal intensive care unit: nested case-control study

The prevalence of permanent childhood hearing impairment (PCHI) in infants admitted to a neonatal intensive care unit (NICU) is higher than that in the general population. Our study objective was to identify risk factors associated with PCHI in infants who required admission to the NICU for more than 48 h. We performed a case-control study, including infants of all gestational ages who were admitted to NICU for more than 48 h and who underwent newborn hearing screening between 2005 and 2019. Infants admitted to NICU and diagnosed with PCHI by formal audiology were classified as "cases". The "controls" were infants who were admitted to NICU and did not have PCHI. Cases and controls (1:4) were matched based on their birth gestation, birthing place, and treating NICU. The prevalence of PCHI in infants admitted to NICU was 6.3% as compared with our general population prevalence of 0.25%. There were 77 cases and 269 controls during the study period. The median age at diagnosis of PCHI in these infants was 132 days (interquartile range 75.5-518.5). Using regression analysis, "any ventilation episodes", presence of seizures, and major congenital anomalies were significantly associated with PCHI in infants of all gestational ages. There were higher prevalence of PCHI in preterms (<32 weeks) who received furosemide and lower prevalence with antenatal use of magnesium sulphate.Conclusions: In our study, the prevalence of hearing loss was high in infants admitted to NICU. Gestation-specific risk factors identified in this case-control study would help in counselling of parents. What is Known: • In the UK, 1-2/1000 infants are born with hearing loss and infants admitted to the neonatal unit for 48 h or more have increased prevalence of hearing loss (1 in 100 live births). • Identification of risk factors in infants admitted to neonatal unit would help with risk stratification and further management. What is New: • In our study, infants admitted to the neonatal unit had higher prevalence of hearing loss (6.3 in 100 live births). • In infants across all gestational age "any ventilation episodes", presence of seizures, and severe congenital anomalies were associated with a statistically significant increase in prevalence of hearing loss. Higher prevalence of hearing loss was noted in preterm infants (<32 weeks) who received furosemide treatment and lower prevalence was noted with antenatal use of magnesium sulphate.