Background:Several observational studies have investigated the association of insomnia with psychiatric disorders. Such studies yielded mixed results, and whether these associations are causal remains unclear. Thus, we aimed to identify the causal relationships between insomnia and five major psychiatric disorders.Methods:The analysis was implemented with six genome-wide association studies; one for insomnia and five for psychiatric disorders (attention-deficit/hyperactivity disorder, autism spectrum disorder, major depressive disorder, schizophrenia, and bipolar disorder). A heterogeneity in dependent instrument (HEIDI) approach was used to remove the pleiotropic instruments, Mendelian randomization (MR)-Egger regression was adopted to test the validity of the screened instruments, and bidirectional generalized summary data-based MR was performed to estimate the causal relationships between insomnia and these major psychiatric disorders.Results:We observed significant causal effects of insomnia on the risk of autism spectrum disorder and bipolar disorder, with odds ratios of 1.739 (95% confidence interval: 1.217–2.486, p = 0.002) and 1.786 (95% confidence interval: 1.396–2.285, p = 4.02 × 10−6), respectively. There was no convincing evidence of reverse causality for insomnia with these two disorders (p = 0.945 and 0.546, respectively). When insomnia was considered as either the exposure or outcome variable, causal estimates for the remaining three psychiatric disorders were not significant.Conclusions:Our results suggest a causal role of insomnia in autism spectrum disorder and bipolar disorder. Future disease models should include insomnia as a factor for these two disorders to develop effective interventions. More detailed mechanism studies may also be inspired by this causal inference.
Background: Snoring is a common condition. Previous studies have reported the relationships between snoring and metabolic syndrome (MetS) and/or its five components: hypertension, hyperglycemia, low-high density lipoprotein (low-HDL), high-triglyceride level, and abdominal obesity. However, conclusions have been inconsistent, and there has been no comprehensive summary on this. Therefore, we performed a systematic review on the relationships between snoring and MetS, including each of MetS' components. Methods: A systematic review and a meta-analysis were conducted following the Meta-analysis of Observational Studies in Epidemiology group and Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines. Electronic databases including PubMed, Embase, and the Cochrane Library were searched for publications from inception to 15 July 2020. The inverse-variance weighted method was used in the meta-analysis to calculate the pooled odds ratios (ORs) and their 95% confidence intervals (CIs) to determine the association between snoring and MetS (and its components) through a fixed or random effect model. A restricted cubic spline regression model and the linear regression model were used in a two-stage dose–response meta-analysis to evaluate the non-linear and the linear trends between snoring frequency and MetS and its components. Results: A total of 40 studies with 966,652 participants were included in this study. The pooled ORs between snoring and MetS and its components, hypertension, hyperglycemia, low-HDL, high-triglyceride level, and abdominal obesity, were 1.61 (95% CI, 1.43–1.78), 1.23 (95% CI, 1.15–1.31), 1.05 (95% CI, 1.04–1.07), 1.09 (95% CI, 1.00–1.18), 1.08 (95% CI, 1.00–1.17), and 1.75 (95% CI, 1.46–2.05), respectively. Non-linear trends were detected in the five associations except for low-HDL. A linear trend was detected in the association of snoring with hypertension, hyperglycemia, low-HDL, or abdominal obesity, with ORs of 1.07 (95% CI, 1.01–1.13), 1.05 (95% CI, 1.02–1.08), 1.03 (95% CI, 1.02–1.04), and 1.17 (95% CI, 1.16–2.89), respectively. Conclusion: Snoring was a risk factor of MetS, and a dose–response relationship existed between the two. Timely intervention in identifying snorers can minimize as much as possible the risk of metabolic syndrome in those who snore.
Although nonalcoholic fatty liver disease (nAfLD) is associated with obstructive sleep apnea syndrome (oSAS), studies on the direct relationship between nAfLD and snoring, an early symptom of oSAS, are limited. We evaluated whether snorers had higher risk of developing nAfLD. the study was performed using data of the Tongmei study (cross-sectional survey, 2,153 adults) and Kailuan study (ongoing prospective cohort, 19,587 adults). In both studies, NAFLD was diagnosed using ultrasound; snoring frequency was determined at baseline and classified as none, occasional (1 or 2 times/week), or habitual (≥3 times/week). Odds ratios (ORs) and hazard ratios (HRs) with 95% confidence intervals were estimated using logistic and Cox models, respectively. During 10 years' follow-up in Kailuan, 4,576 individuals with new-onset NAFLD were identified at least twice. After adjusting confounders including physical activity, perceived salt intake, body mass index (BMi), and metabolic syndrome (MetS), multivariate-adjusted oRs and HRs for nAfLD comparing habitual snorers to non-snorers were 1.72 (1.25-2.37) and 1.29 (1.16-1.43), respectively. These associations were greater among lean participants (BMi < 24) and similar across other subgroups (sex, age, MetS, hypertension). Snoring was independently and positively associated with higher prevalence and incidence of nAfLD, indicating that habitual snoring is a useful predictor of nAfLD, particularly in lean individuals. Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide 1. NAFLD affects approximately 25% of the global population 2 , with more than 10% of cases occurring in lean people 1. The prevalence of NAFLD ranges from 6.3% to 27.0% in Chinese adults 3 and is increasing at a rate of 0.594% per year 4. The rising prevalence of NAFLD, in conjunction with the pandemic of obesity and metabolic syndrome (MetS), represent an increasing global public health burden 5. Snoring is a common condition that is easily detected by co-sleepers. In a recent study among 10,139 people living in rural areas of northern China, 47.2% of men and 37.8% of women self-reported snoring 6. Several meta-analyses have revealed that snoring is associated with higher risks of diabetes 7 , gestational diabetes mellitus, pregnancy-induced hypertension and preeclampsia 8 , cardiovascular disease, and all-cause mortality 9,10. Multiple randomized controlled trials have suggested a possible causal relationship between obstructive sleep apnea syndrome (OSAS) and NAFLD 2,11. Snoring is an early symptom of OSAS; 12 however, to our knowledge, few studies have investigated the direct relationships between self-reported snoring and NAFLD. Thus, we conducted the first cross-sectional study and first independent validation cohort study designed to investigate whether individuals who self-reported snoring had a higher prevalence and incidence of NAFLD. Low-to-moderate alcohol intake may have beneficial effects in patients with NAFLD 13,14. Conversely, alcohol increases upper air...
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