Abstract
This cohort study evaluates the association between frequency and trajectories of vasomotor symptoms with incident type 2 diabetes among premenopausal or perimenopausal women in the US.
Introduction
Vasomotor symptoms (VMS; night sweats and hot flashes) are the hallmark signs of menopause. Growing evidence suggests an association between VMS and the increased cardiometabolic risk experienced in women during and after the menopausal transition (MT).1 While most women experience VMS,2 the frequency and the temporal patterns vary dramatically across subgroups of women.3 Past studies examined the association of VMS at 1 time point with diabetes; thus, it remains unknown whether VMS trajectories across the MT are associated with risk of type 2 diabetes (T2D). We examined the associations of frequency and trajectories of VMS with incident T2D over the MT in the Study of Women’s Health Across the Nation (SWAN).
Methods
SWAN is a prospective cohort of US women who were premenopausal or early perimenopausal at baseline and assessed at up to 13 approximately annual follow-up visits at 7 clinical sites (eTable).4 All protocols were approved by the sites’ institutional review boards, and all study participants provided informed written consent. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline. The analytic sample excluded participants who had diabetes or used exogenous hormones at baseline, did not have any follow-up visits or at least 3 visits before diabetes diagnosis, or were missing VMS information.
At each follow-up visit, participants reported how often they experienced hot flashes and/or night sweats in the past 2 weeks. Women were defined as having diabetes at each visit if they reported use of antidiabetic medication, had 2 consecutive visits with fasting glucose 126 mg/dL (to convert to mmol/L, multiply by .0555) or more while not receiving steroids, or had 2 visits with self-reported diabetes and 1 visit with fasting glucose 126 mg/dL or more (eMethods in Supplement 1).
We tested associations between VMS and VMS trajectories and incident diabetes using discrete-time hazard models5 via fitted generalized linear models with a complementary log-log link to generate hazard ratios (HRs) and 95% CIs. VMS were also modeled using a group-based trajectory approach6 to identify VMS patterns during follow-up. All models were adjusted for time (study visit) and site; minimally adjusted models included self-reported race and ethnicity (Black, Chinese, Hispanic, Japanese, and White; assessed because of concerns regarding differences in health outcomes across these groups), baseline age and educational attainment, and time-varying body mass index (BMI), physical activity, smoking status, alcohol consumption, and MT stage; fully adjusted models additionally included sex hormones (eMethods in Supplement 1). Analyses were conducted in RStudio version 2023.09.1 (R Project for Statistical Computing). All results were considered statistically significant at a 2-sided P ≤ .05. Data were analyzed from January 2021 to June 2024.
Results
A total of 2761 SWAN participants at baseline were midlife and racially and ethnically diverse (mean [SD] age, 46 [3] years; 737 [27%] Black, 265 [9.6%] Japanese, and 1345 [49%] White) (Table 1). At baseline, 764 (28%) reported VMS 1 to 5 days per 2-week period, 280 (10%) reported VMS 6 or more days per week, and 1716 (62%) reported no VMS; 338 (12.2%) developed diabetes during follow-up (Table 1).
Table 1. Baseline Characteristics of Study Sample From Study of Women’s Health Across the Nation Population.
| Characteristic | Patients, No. (%) (N = 2761) |
|---|---|
| Age, mean (SD), y | 46 (3) |
| Vasomotor symptom frequency, any | |
| None | 1716 (62) |
| 1-5 d per 2 weeks | 764 (28) |
| ≥6 d per 2 weeks | 280 (10) |
| VMS trajectory class, any | |
| Consistently low | 704 (26) |
| Consistently high | 846 (31) |
| Early onset | 694 (25) |
| Late onset | 512 (19) |
| Unknown | 5 (0.2) |
| Race and ethnicity | |
| Black | 737 (27) |
| Chinese | 234 (8.5) |
| Hispanic | 180 (6.5) |
| Japanese | 265 (9.6) |
| White | 1345 (49) |
| Education | |
| High school or less | 601 (22) |
| Some college | 871 (32) |
| ≥4-y College | 1265 (46) |
| Annual household income, US $ | |
| Less than 10 000 | 139 (5.2) |
| 10 000-19 999 | 195 (7.3) |
| 20 000-34 999 | 412 (15) |
| 35 000-49 999 | 490 (18) |
| 50 000-74 999 | 639 (24) |
| 75 000-99 999 | 376 (14) |
| 100 000-149 999 | 310 (12) |
| ≥150 000 | 126 (4.7) |
| Menopausal transition stage | |
| Premenopause | 1524 (55) |
| Early perimenopause | 1237 (45) |
| Body mass index, mean (SD)a | 28 (7) |
| Smoking status | |
| Never smoked | 1611 (58) |
| Past only | 708 (26) |
| Current smoker | 442 (16) |
| Alcohol use | |
| None | 1323 (48) |
| <1 drink per week | 302 (11) |
| 1-7 drinks per week | 728 (26) |
| >7 drinks per week | 405 (15) |
| Physical activity score, mean (SD)b | 7.73 (1.77) |
| Sex hormone-binding globulin, median (IQR), µg/mL | 3.99 (2.76-5.51) |
| Testosterone, median (IQR), ng/dL | 41 (30-56) |
| Free Androgen Index, median (IQR) | 3.4 (2.1-5.8) |
SI conversion factor: To convert testosterone to nmol/L, multiply by 0.0347; sex hormone-binding globulin to nmol/L, multiply by 8.896.
Calculated as weight in kilograms divided by height in meters squared.
Physical activity score is the sum of 3 indices of sports and exercise, active living, and household/caregiving domains of physical activity. The values of the score range from 3 to 15.
More frequent time-varying VMS were associated with increased risk of incident diabetes (relative to no VMS: frequent VMS HR, 1.45; 95% CI, 1.11-1.95; infrequent VMS HR, 1.30; 95% CI, 1.00-1.70), adjusted for covariates (Table 2). Four VMS trajectories were identified, with some patient falling into a fifth, unknown category: (1) consistently low probability of VMS (704 patients [26%]), (2) persistently high probability of VMS (846 patients [31%]), (3) early onset-initial high probability of VMS that decreased over time (694 patients [25%]), (4) late onset-initial low probability of VMS that increased over time (512 patients [19%]), and unknown (5 patients [0.2%]). Women with persistently high VMS had an increased risk of diabetes compared with consistently low VMS (HR, 1.50; 95% CI, 1.12-2.02). Results were similar for both hot flashes and night sweats (Table 2).
Table 2. Crude and Adjusted Hazard Ratio (HR) of Incident Diabetes by Frequency of Any Vasomotor Symptoms (VMS) at Baseline and Time-Varying and by VMS Trajectoriesa,b.
| Frequency or trajectory of symptoms | HR (95% CI) | ||
|---|---|---|---|
| Unadjusted | Adjusted model 1b | Adjusted model 2c | |
| Frequency of any VMS | |||
| Baseline: None | 1 [Reference] | 1 [Reference] | 1 [Reference] |
| Baseline: 1-5 d per 2 weeks | 1.17 (0.91-1.49) | 1.07 (0.83-1.38) | 1.03 (0.80-1.33) |
| Baseline: ≥6 d per 2 weeks | 1.71 (1.26-2.35) | 1.25 (0.91-1.73) | 1.21 (0.88-1.67) |
| Time-varying: none | 1 [Reference] | 1 [Reference] | 1 [Reference] |
| Time-varying: 1-5 d per 2 weeks | 1.20 (0.93-1.56) | 1.30 (1.00-1.70) | 1.26 (0.97-1.63) |
| Time-varying: ≥6 d per 2 weeks | 1.34 (1.02-1.77) | 1.45 (1.11-1.95) | 1.41 (1.05-1.87) |
| Frequency of hot flashes | |||
| Baseline: none | 1 [Reference] | 1 [Reference] | 1 [Reference] |
| Baseline: 1-5 d per 2 weeks | 1.54 (1.20-1.98) | 1.38 (1.06-1.78) | 1.34 (1.04-1.73) |
| Baseline: ≥6 d per 2 weeks | 1.61 (1.13-2.29) | 1.20 (0.83-1.74) | 1.20 (0.83-1.73) |
| Time-varying: none | 1 [Reference] | 1 [Reference] | 1 [Reference] |
| Time-varying: 1-5 d per 2 weeks | 1.17 (0.91-1.52) | 1.27 (0.98-1.65) | 1.23 (0.95-1.60) |
| Time-varying: ≥6 d per 2 weeks | 1.27 (0.96-1.68) | 1.35 (1.01-1.79) | 1.30 (0.97-1.73) |
| Frequency of night sweats | |||
| Baseline: none | 1 [Reference] | 1 [Reference] | 1 [Reference] |
| Baseline: 1-5 d per 2 weeks | 1.03 (0.79-1.34) | 0.90 (0.68-1.18) | 0.90 (0.68-1.18) |
| Baseline: ≥6 d per 2 weeks | 1.56 (1.07-2.28) | 1.14 (0.77-1.68) | 1.09 (0.74-1.62) |
| Time-varying: none | 1 [Reference] | 1 [Reference] | 1 [Reference] |
| Time-varying: 1-5 d per 2 weeks | 1.09 (0.84-1.42) | 1.18 (0.90-1.55) | 1.14 (0.87-1.49) |
| Time-varying: ≥6 d per 2 weeks | 1.44 (1.06-1.95) | 1.55 (1.13-2.12) | 1.46 (1.07-2.00) |
| VMS trajectories | |||
| Any VMS | |||
| Persistently high (n = 846) | 1.47 (1.11-1.95) | 1.50 (1.12-2.02) | 1.42 (1.06-1.92) |
| Early onset (n = 694) | 0.87 (0.62-1.20) | 0.83 (0.59-1.16) | 0.77 (0.56-1.08) |
| Late onset (n = 512) | 0.76 (0.52-1.10) | 0.98 (0.67-1.44) | 0.97 (0.66-1.43) |
| Consistently low (n = 704) | 1 [Reference] | 1 [Reference] | 1 [Reference] |
| Hot flashes | |||
| Persistently high (n = 707) | 1.51 (1.16-1.96) | 1.64 (1.25-2.17) | 1.56 (1.18-2.05) |
| Early onset (n = 658) | 0.85 (0.62-1.15) | 1.27 (0.92-1.75) | 1.28 (0.93-1.76) |
| Late onset (n = 532) | 1.03 (0.75-1.41) | 1.02 (0.74-1.42) | 0.94 (0.67-1.30) |
| Consistently low (n = 864) | 1 [Reference] | 1 [Reference] | 1 [Reference] |
| Night sweats | |||
| Persistently high (n = 514) | 1.93 (1.36-2.73) | 1.86 (1.30-2.67) | 1.73 (1.21-2.48) |
| Early onset (n = 521) | 1.49 (1.03-2.17) | 1.33 (0.91-1.95) | 1.22 (0.83-1.79) |
| Late onset (n = 1157) | 1.43 (1.02-2.00) | 1.21 (0.86-1.72) | 1.23 (0.87-1.74) |
| Consistently low (n = 564) | 1 [Reference] | 1 [Reference] | 1 [Reference] |
Crude/unadjusted model includes site and site visit number as covariates.
Model adjusted for site, visit number, race and ethnicity, baseline age and education, time-varying body mass index, physical activity score, smoking status, alcohol consumption, and menopause transition stage.
Model further adjusted for sex hormone binding globulin and testosterone levels at baseline.
Discussion
The study was limited to women with at least 3 visits before diabetes diagnosis to quantify trajectories; therefore, women who have a short time from VMS onset to diabetes are not represented. Women who had different patterns of VMS in the past 2 weeks from the other parts of the year may have been misclassified. SWAN did not measure hemoglobin A1C, which is typically used to diagnose diabetes.
In this prospective cohort study, frequent VMS or a trajectory of persistent VMS were associated with a 50% increased risk of diabetes. Women with frequent and/or persistent VMS over the MT may represent a high-risk group to target for diabetes prevention.
eMethods. Diabetes Ascertainment
eTable. Number of SWAN Women Contributing to the Analysis at Each SWAN Visit
eReferences
Data Sharing Statement
References
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
eMethods. Diabetes Ascertainment
eTable. Number of SWAN Women Contributing to the Analysis at Each SWAN Visit
eReferences
Data Sharing Statement
