Tryptophan modulates the impact of prolactin on insomnia in perimenopausal women: a cross-sectional study

Background Insomnia is highly prevalent among perimenopausal women and exerts detrimental effects on physical health, psychological well-being, and overall quality of life. However, its underlying mechanisms remain incompletely understood. This cross-sectional study aimed to identify factors associated with insomnia in perimenopausal women. Methods A total of 187 perimenopausal women aged 45–55 years were enrolled. Insomnia, anxiety, and depression severity were assessed using the Insomnia Severity Index (ISI), Generalized Anxiety Disorder-7 (GAD-7), and Patient Health Questionnaire-9 (PHQ-9), respectively. Serum levels of relevant amino acids and hormones were measured. Spearman correlation and linear regression analyses were performed to examine the associations among prolactin levels, tryptophan levels, insomnia, anxiety, and depression. Moderation analysis was further conducted to evaluate the potential moderating role of tryptophan in these relationships. Results Serum prolactin levels were positively associated with scores of ISI, GAD-7, and PHQ-9. Furthermore, prolactin levels were positively correlated with the severity of sleep-onset difficulties, sleep maintenance problems, noticeability of impairment, and sleep-related distress. Of note, serum tryptophan levels significantly moderated the association between prolactin levels and ISI scores ( β = 0.227, 95% CI = 0.04–0.41, p = 0.0148). To wit, he positive relationship between prolactin levels and insomnia severity was stronger in perimenopausal women with higher serum tryptophan levels compared with those with lower levels. Conclusions The moderating effect of serum tryptophan on the relationship between prolactin levels and insomnia in perimenopausal women helps us understand the neuroendocrine mechanisms underlying perimenopausal insomnia and may inform future research on targeted preventive and therapeutic strategies.