Causal Relationship Between Sleep Characteristics and Alopecia Areata and Other Non-Scarring Alopecia: A Two-Sample Bidirectional Mendelian Randomization Analysis

Nov 11, 2025Clinical, cosmetic and investigational dermatology

Possible two-way links between sleep patterns and non-scarring hair loss, including alopecia areata

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Abstract

Genetically predicted insomnia is associated with a 3.88 times higher risk of .

Alopecia areata may be linked to genetically predicted morningness, with an odds ratio of 1.0102.
Non-scarring alopecia is associated with reduced sleep duration, indicated by an odds ratio of 0.9881.
Cochran's Q test indicates heterogeneity in the genetic effects related to scarring alopecia and daytime napping.
Multiple testing corrections affected the significance of observed associations.
Bidirectional causal relationships between alopecia and sleep characteristics warrant careful interpretation.

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BACKGROUND: Previous studies have indicated an association between alopecia and sleep characteristics, but the causality is not clear. This study aimed to investigate the potential causal relationship between four sleep traits (morningness, sleep duration, insomnia, daytime napping) and four subtypes of alopecia (, androgenic alopecia, scarring, and other non-scarring alopecia).

METHODS: A bidirectional (MR) analysis based on genome-wide association studies (GWAS) data was employed to examine the causal relationship between alopecia and sleep characteristics. Sample sizes ranged from 209 to 452,633 participants for different traits. Various analytical approaches, including Inverse Variance Weighted (IVW), Weighted Median, MR-Egger and Weighted Mode were employed. Instrumental variables were selected based on conventional significance thresholds (P < 5 × 10for sleep traits) and structured criteria for alopecia. A Bonferroni correction was applied to account for multiple testing. Sensitivity analyses, including Cochran's Q, leave-one-out, and MR pleiotropy residual sum and outlier (MR-PRESSO) methods, were subsequently conducted to affirm the robustness of the findings. -8

RESULTS: IVW method suggested causal associations between genetically predicted insomnia and a higher risk of alopecia areata (OR (95% CI) = 3.88 (1.5-10.04), P = 0.01), genetically predicted alopecia areata and morningness (OR (95% CI) = 1.0102 (1.0005-1.0201), P = 0.04), as well as genetically predicted non-scarring alopecia and reduced sleep duration (OR (95% CI) = 0.9881 (0.9767-0.9997), P = 0.04). However, these associations did not survive multiple testing correction. Cochran's Q test revealed heterogeneity in the analysis between scarring alopecia and daytime nap (Q = 39.29, P = 0.01), indicating potential variability in the genetic effects across different SNPs. Based on MR-PRESSO and leave-one-out analyses, outliers were removed, revealing no evidence of horizontal pleiotropy in this study.

CONCLUSION: This MR study suggests potential bidirectional causal associations between alopecia and sleep characteristics. However, the findings should be interpreted cautiously due to multiple testing considerations. Future work should investigate mechanisms and generalize findings across populations.

Key numbers

3.88

Increase in Risk of

Odds ratio for genetically predicted insomnia.

1.0102

Nominal Association with Morningness

Odds ratio for affecting morningness.

0.9881

Decrease in Sleep Duration

Odds ratio for genetically predicted non-scarring alopecia.

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Causal Relationship Between Sleep Characteristics and Alopecia Areata and Other Non-Scarring Alopecia: A Two-Sample Bidirectional Mendelian Randomization Analysis

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