Mendelian randomization analyses for the causal relationship between early age at first sexual intercourse, early age at first live birth, and postpartum depression in pregnant women

Introduction

There are insufficient epidemiological studies on the impact of age at first sexual intercourse (AFS) and age at first live birth (AFB) on postpartum depression (PPD) in pregnant women, and the conclusions of these studies are inconsistent.

Methods

We performed a Mendelian randomization (MR) study to determine the causal relationship between AFS or AFB and the risk of PPD. The summary data were extracted from genome-wide association study (GWAS) summary datasets. We selected the instrumental variables according to the P value of exposure-related single nucleotide polymorphisms (P<5 ×10-9 for AFS and P<5 ×10-8 for AFB) and estimated the linkage disequilibrium using the clump parameter (10,000 kb, r2 < 0.001). Single nucleotide polymorphisms were considered instrumental variables that were significantly associated with exposure factors without linkage disequilibrium. The F-statistics of the instrumental variables should all be larger than 10. A random-effects model of IVW was constructed as the main method in our study.

Results and discussion

MR studies based on GWAS data revealed that both AFS (OR = 0.4, P <0.001) and AFB (OR = 0.38, P <0.001) were negatively correlated with the risk of PPD. Early AFS and early AFB should be studied as possible risk factors for PPD in the future. Public health departments should attach importance to sex education for young girls. The results of our TSMR should be verified by high-quality prospective epidemiological studies in the future.

Exploring the causal relationship between female reproductive traits and frailty: a two-sample mendelian randomization study

Background: The impact of female reproductive factors, including age at menarche (AAM), age at first birth (AFB), age at first sexual intercourse (AFS), age at natural menopause (ANM), and pregnancy abortion (PA), on the risk of developing frailty remains uncertain. Our objective is to examine the potential causal relationship between female reproductive traits and frailty through the utilization of two-sample univariable Mendelian Randomization (UVMR) and multivariable Mendelian Randomization (MVMR) analyses. Methods: Leveraging large-scale Genome-Wide Association Study (GWAS) data from individuals of European ancestry, we performed two-sample UVMR and MVMR analyses to examine the causal relationship between female reproductive traits and frailty. The primary analysis employed inverse-variance-weighted (IVW) estimation, and sensitivity analyses were conducted to assess the robustness of the findings. Results: The UVMR analysis revealed a significant causal relationship between female reproductive traits (AFS, AFB, AAM) and frailty [IVW: OR = 0.74, 95%CI(0.70-0.79), p = 0.000; OR = 0.93, 95%CI(0.92-0.95), p = 0.000; OR = 0.96, 95%CI(0.95-0.98), p = 0.000]. However, there was no significant effect of ANM and PA on frailty (p > 0.05). The sensitivity analysis results were robust, supporting the findings. Furthermore, this association remained significant even after adjusting for body mass index (BMI) and educational attainment (EA) in the MVMR analysis [IVW: OR = 0.94, 95%Cl (0.91-0.97), p = 0.000; OR = 0.77, 95%Cl (0.70-0.86), p = 0.000; OR = 0.95, 95%Cl (0.94-0.97), p = 0.000]. BMI and EA serve as mediators in this process. Conclusion: Our research has established a significant causal relationship between female reproductive traits (AFS, AFB, AAM) and frailty, with BMI and EA acting as mediating factors in this process. However, further research is warranted to validate our findings and elucidate the underlying biological mechanisms.

Assessing the association between age at first sexual intercourse and migraine: a Mendelian randomization study

Background and objectives

As indicated by observational and genetic variation studies, age at first sexual intercourse (AFS) may be associated with migraine attack, but there is a lack of evidence from real-world studies due to ethical concerns. Therefore, we conducted a Mendelian randomization study to determine the causal relationship between AFS and migraine.

Methods

We extracted instrumental variables from summary data of a genome-wide association study (GWAS) on AFS and migraine and then conducted two-sample Mendelian randomization analyses. GWAS data for AFS and migraine were obtained from 397,338 unrelated individuals (214,547 females and 182,791 males) and 306,314 individuals (18,477 patients and 287,837 control individuals), respectively.

Results

There was a causal relationship between AFS and risk for migraine (odds ratio (OR) = 0.73, 95% confidence interval (CI) [0.61 to 0.86]), both for migraine with aura (MWA; OR = 0.72, 95% CI [0.58 to 0.89]) and migraine without aura (MOA; OR = 0.66, 95% CI [0.51 to 0.86]). Stratified analyses provided suggestive evidence of the causal relationship between delayed AFS and a decreased risk of migraine for both males (OR = 0.71, 95% CI [0.59 to 0.84]) and females (OR = 0.73, 95% CI [0.61 to 0.89]). Reverse Mendelian randomization did not reveal any effect of migraine on AFS (p > 0.05). No pleiotropy was detected.

Discussion

A delayed AFS is a protective factor against migraine (for both MWA and MOA) in both males and females. This causal relationship indicates the presence of extracranial regulatory pathways of migraine.

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.

Temporal Trends and Differences in Sexuality among Depressed and Non-Depressed Adults in the United States

This study aimed to examine temporal trends and differences in sexuality between depressed and non-depressed adults aged 18-59 in the United States from 2005 to 2016. A total of 21,437 people (5432 with depression) were enrolled in this cross-sectional study. From 2005-2008 to 2013-2016, the average age at first sexual intercourse decreased, while the proportion of normal frequency of sexual activity and heterosexual sexual orientation increased among all the participants. Some differences in sexuality were found between the depressed and non-depressed groups. The average age at first sexual intercourse (p < 0.001), the proportion of normal frequency of sexual activity (p < 0.001), and heterosexual sexual orientation (p < 0.001) were lower in depressed participants, and the differences did not change over time (p_{for trend} = 0.926 of average age at first sexual intercourse, p_{for trend} = 0.823 of normal frequency of sexual activity, p_{for trend} = 0.926 of heterosexual sexual orientation). Moreover, these differences were associated with marital status (p_{for interaction} < 0.001 by average age at first sexual intercourse), employment status (p_{for interaction} < 0.001 by average age at first sexual intercourse), education status (p_{for interaction} = 0.023 by heterosexual sexual orientation) and family income status (p_{for interaction} = 0.013 by average age at first sexual intercourse and p_{for interaction} = 0.017 by normal frequency of sexual activity). In conclusion, the study found that the age at first sexual intercourse decreased and the frequency of sexual intercourse increased in all the participants, and differences in sexuality between depressed and non-depressed participants were present; however, these differences had no further increase or decrease during the 12-year period. These differences were associated with marital status, employment status, education status, and family income status. These findings show differences in sexuality between depressed and non-depressed patients but are somewhat different from previous studies; the results may provide directions for future research and social work.

How Can Unintended Pregnancies Be Prevented among Adolescents Who Engaged in Sexual Intercourse at Earlier Ages? The Role of Female Education and Partner Age Difference

Several studies have identified explicative factors for adolescents' sexual risk behaviors and related outcomes such as unintended pregnancy; however, less is known about the mechanisms through which such factors act. Our study explored the role of female education and partner age difference as explicative mechanisms of the association between age at first sexual intercourse (AFSI) and unintended pregnancy while controlling for the role of other contextual factors (i.e., socioeconomic status, ethnicity, religious beliefs, and place of residence) and sexual-related mechanisms (i.e., number of sexual partners) that are known to be associated with adolescent pregnancy. The sample consisted of 613 sexually experienced female adolescents who did not intend to become pregnant: 349 were pregnant for the first time, and 264 had never been pregnant. Mediation and moderation analyses were performed. An earlier AFSI was associated with unintended pregnancy 1-6 years after first sexual intercourse by increasing the adolescents' likelihood of having less education and being involved with partners older than themselves. There was no significant direct effect of AFSI on pregnancy occurrence after controlling for the mediators. Our findings bring to light nonsexual mechanisms that must be considered in public health interventions aimed at preventing unintended pregnancies among adolescents who engaged in sexual intercourse at early ages. Specific implications are discussed.

Trends in Sexual Behaviour in Czech Schoolchildren between 2002-2014

OBJECTIVE

The aim of this study was to report on trends in the prevalence in age at first intercourse of Czech schoolchildren and a difference between sexes.

METHODS

Prevalence in age at first intercourse of Czech schoolchildren was observed under the Health Behaviour in School-aged Children study in the years 2002, 2006, 2010 and 2014. In addition, a random representative sample of children attending 9th grade completed the questions related to sexual behaviour. A total of 4,804 boys and girls at the age of 15 years were included in the study. The chi-square test and analysis of variance were used for data assessment.

RESULTS

Experience with first sexual intercourse before 15 years was confirmed by 16% of boys and 19.4% of girls. Average age of coitarche in both sexes most often ranged between 14 and 15 years. Since 2006 boys had significantly lower age at coitarche. Only in 2010 the girls had first intercourse more frequently than boys. Since 2010 the number of Czech adolescents of both sexes having first intercourse before the age of 15 years has significantly increased. However, a rise in average age of coitarche over 15 years in both sexes occurred in 2014.

CONCLUSIONS

The number of Czech children having a sexual intercourse before 15 years has significantly increased since 2010.