Early sexual experience and hypertension in US adults: results from the National Health and Nutrition Examination Survey 2001-2016

Causal effects of female reproductive features on nonalcoholic fatty liver disease: A mendelian randomization study

BACKGROUND AND AIMS

Epidemiological evidence on the associations between female reproductive features and nonalcoholic fatty liver disease (NAFLD) is conflicting. To explore their causalities, we conducted a Mendelian randomization (MR) study.

METHODS

Summary-level data were obtained, and univariable MR was performed to explore the causalities between female reproductive features and NAFLD. And we performed multivariable MR and MR mediation analysis to explore the mediation effects of educational attainment (EA) and body mass index (BMI) for these associations. Sensitivity analyses were performed to evaluate pleiotropy and heterogeneity.

RESULTS

There were causal effects of age at menarche (AAMA) (odds ratio [OR]: 0.817, 95% confidence interval [CI]: 0.736-0.907, per year-increase), age at first birth (AFB) (OR: 0.851, 95%CI: 0.791-0.926, per year-increase) and age at first sexual intercourse (AFS) (OR: 0.676, 95%CI: 0.511-0.896, per standard deviation-increase) on NAFLD risk. Besides, the causal effects were also observed on NAFLD phenotypes including liver fat content (LFC) and alanine aminotransferase (ALT). Further mediation analysis showed that BMI mediated partial proportion of effects of AAMA and AFS on NAFLD/ALT, AFB on NAFLD/LFC/ALT, while EA mediated partial proportion of effects of AFB on NAFLD/LFC/ALT, and AFS on NAFLD/ALT.

CONCLUSIONS

This study provided convincing evidence that early AAMA, AFB, and AFS were risk factors for NAFLD. Reproductive health education, obesity management, and education spread might be the beneficial strategies for NAFLD prevention.

Association of age at first sexual intercourse and lifetime number of sexual partners with cardiovascular diseases: a bi-directional Mendelian randomization study

Background

Limited studies have explored the association between sexual factors [age at first sexual intercourse (AFS) and lifetime number of sexual partners (LNSP)] and cardiovascular diseases (CVDs), leaving the causality inconclusive.

Methods

We performed a bi-directional Mendelian randomization (MR) study to investigate the causality between sexual factors and CVDs, including coronary artery disease, myocardial infarction, atrial fibrillation (AF), heart failure (HF), and ischemic stroke (IS). Single-nucleotide polymorphisms (SNPs) for sexual factors were extracted from the UK Biobank. Statistics for each CVD were derived from two different databases. MR estimates were calculated per outcome database and were combined through meta-analysis. Several complementary sensitivity analyses were also performed.

Results

The primary analysis suggested that AFS was causally associated with the risk of CVDs; the odds ratios (ORs) ranged from 0.686 [95% confidence interval (CI), 0.611-0.770] for HF to 0.798 (95% CI, 0.719-0.886) for AF. However, the association between AFS and IS (OR, 0.844; 95% CI, 0.632-1.126) was not consistent in the meta-analysis after excluding SNPs related to confounders. Moreover, non-significant associations were found between LNSP and CVDs. Reverse direction MR analysis showed that CVDs were not associated with sexual factors.

Conclusions

Genetic evidence suggested that AFS was causally associated with the risk of CVDs except for IS, whereas non-significant association of LNSP with CVDs was detected. Further investigation into AFS could be warranted in preventing the progression of CVDs.

Sexual behavior and cardiovascular diseases: univariable and multivariable Mendelian randomization

Background

To assess the relationship of genetically predicted sexual behavior (age at first sex (AFS) and the number of sexual partners (NSP)) on cardiovascular diseases (CVDs).

Methods and results

We performed two-sample Mendelian randomization (MR) with publicly available datasets from the UK Biobank and FinnGen Study, and analyzed genome-wide association results for sexual behaviors and twelve types of CVDs. The univariable MR method provided a total effect of AFS and NSP on CVDs, and showed evidence that early AFS rather than NSP was associated with CVDs, including angina pectoris (AP), atrial fibrillation and flutter (AFF), coronary atherosclerosis (CAS), deep vein thrombosis of the lower extremity (DVT-LE), heart failure (HF), hypertension (HTN), ischaemic stroke (IS), and myocardial infarction (MI). Given sex as a social determinant of CVD risk, we used gender-stratified SNPs to investigate gender differences in the development of CVDs. These results showed a stronger causal relationship of AFS on CVDs in females than in males. Further multivariable MR analyses indicated a direct effect after accounting for insomnia, number of days of vigorous physical activity 10 + minutes (VPA 10 + min), and time spent watching television (TV). Two-step MR demonstrated these three risk factors act as a mediator in AFS associated AP/HTN/HF.

Conclusions

We provide evidence that early AFS increased the risk of CVDs. These associations may be partly caused by VPA 10 + min, insomnia, and the time spent on TV. The causality of AFS on CVDs in females was stronger than in males. Conversely, genetically predicted NSP was not associated with CVDs.