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. 2020 Jan;27(1):5-13.
doi: 10.1097/GME.0000000000001420.

Monthly variation of hot flashes, night sweats, and trouble sleeping: effect of season and proximity to the final menstrual period (FMP) in the SWAN Menstrual Calendar substudy

Siobán D Harlow  1 , Michael R Elliott  2 , Irina Bondarenko  2 , Rebecca C Thurston  3 , Elizabeth A Jackson  4
Affiliations

Monthly variation of hot flashes, night sweats, and trouble sleeping: effect of season and proximity to the final menstrual period (FMP) in the SWAN Menstrual Calendar substudy

Siobán D Harlow et al. Menopause. 2020 Jan.

Abstract

Objective: Although reproductive function is influenced by season, few studies have evaluated seasonal effects on menopausal symptoms. We assessed the impact of season and proximity to the final menstrual period (FMP) on frequency of symptom reporting.

Methods: In all, 955 participants in the Study of Women's Health Across the Nation recorded whether or not they had experienced menopausal symptoms on a monthly menstrual calendar over a 10-year period. We modeled the log-odds of presence of a given symptom each month using a logistic mixed-effects model, assuming a third-order polynomial before the FMP and a different third-order polynomial after the FMP. We assumed sine and cosine functions for month of the year.

Results: Five to 10 years before the FMP, ∼20% of women reported hot flashes and night sweats, whereas ∼40% reported trouble sleeping. Prevalence rose ∼4 years before the FMP with a sharp jump in hot flash (∼60%) and night sweats (∼40%) prevalence coincident with the FMP. Peaks in hot flashes and trouble sleeping were observed in July with troughs in January. The peak and trough in night sweats occurred about 1 month earlier. Odds of hot flashes, night sweats, and trouble sleeping were 66%, 50%, and 24% greater, respectively, at the seasonal peak versus the seasonal minimum.

Conclusion: Menopausal symptoms exhibit seasonal variation associated with the summer and winter equinoxes. Seasonal increases in night sweats precede increases in hot flashes. Prospectively recorded monthly symptom data demonstrate that hot flashes and night sweats increase notably coincident with the FMP. : Video Summary:http://links.lww.com/MENO/A476.

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Conflict of interest statement

Financial disclosures/conflicts of interest:

SDH: American Reagent (Medical Advisory Board); RCT: Pfizer, Proctor and Gamble, MAS Innovations (consulting); ME,IB, EAJ report no conflicts of interest.

Figures

Figure 1:
Figure 1:
Histograms of the monthly prevalence of hotflashes, night sweats, and trouble sleeping in relation to time before and after the final menstrual period (FMP): the Study of Women’s Health Across the Nation (SWAN) (n=955).
Figure 2.
Figure 2.
Odds ratio for reporting of hot flash, night sweats, and trouble sleeping by month, the Study of Women’s Health Across the Nation (SWAN) (n=955). Peaks for hot flash and trouble sleeping reporting occur in July and for night sweats in May while troughs occur in January and November, respectively.
Figure 3.
Figure 3.
Estimated within-woman trends in the probability of reporting hot flashes, night sweats and trouble sleeping in relation to time before and after the final menstrual period (FMP) by smoking status at baseline, race/ethnicity and ever hormone use, the Study of Women’s Health Across the Nation (SWAN) (n=955).
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Comment in

  • Seasonality and symptoms.
    Landis CA, Woods NF. Landis CA, et al. Menopause. 2020 Jan;27(1):1-2. doi: 10.1097/GME.0000000000001470. Menopause. 2020. PMID: 31880676 No abstract available.

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