In the journal Menopause is a study about the effects of stopping hormone therapy on sleep in women going through menopause. Researchers analyzed data from 1405 women (average age 60 years) who were randomized to either continue their hormone therapy, stop it for one month, or stop it for two months. The women filled out sleep questionnaires at the beginning of the study and three months later.
The results showed that compared to the women who continued therapy, those women who stopped therapy for two months reported 46% more days with trouble falling asleep and sleeping poorly, and 31% more days waking too early. The effect on sleep of the one month therapy stoppage was less pronounced but still statistically significant. The results held up even when potentially confounding factors like alcohol use, body mass index, age, race, and ethnicity were taken into account.
The researchers hypothesized that the women who stopped therapy had insomnia symptoms because of a return of vasomotor symptoms like hot flashes. This could be true and I also think there could be another contributor. Female hormones have been shown to improve muscle tone in the upper airway, which could theoretically reduce obstructive sleep apnea. It could be that stopping the female hormones cause the women to experience more insomnia from a worsening of underlying obstructive sleep apnea.
The take home message is that if you are going to stop female hormone therapy, be prepared for potential worsening of sleep quality. Instead of reaching for a sleep aid, discuss your symptoms with your doctor first.