The findings from this cross-sectional survey of women age 40 to 65 suggest that potentially modifiable factors, such as BMI, alcohol intake, smoking, and dietary fat intake, may alter the risk of having hot flashes. The impact of these factors on hot flashes may differ by menopausal status.
In our analysis, perimenopausal women with a BMI of ≥25 kg/m2
were more likely to report hot flashes than women with a BMI of <25 kg/m2
. Body mass index was not associated with hot flashes in postmenopausal women. The observation that women with a BMI above normal range (18.5 to 24.9 kg/m2
) experience more bothersome hot flashes than women with a normal BMI is supported by multiple studies.7–11
In three of these studies, high BMI was associated with hot flashes in perimenopausal women but not in postmenopausal women. In 1996, den Tonkelaar et al. found that women age 40 to 44 with a BMI ≥25 kg/m2
experienced more hot flashes than women with a BMI <22 kg/m2
(odds ratio [OR], 1.70; 95% confidence interval [CI], 1.30 to 2.21); hot flashes of women age 54 to 69 years were not associated with BMI (OR, 0.85; 95% CI, 0.52 to 1.36).7
Similarly, in a subgroup analysis of the Study of Women Across the Nation (SWAN), early perimenopausal women with a BMI ≥27 kg/m2
had an increased risk of hot flashes (OR, 1.15; 95% CI, 1.04 to 1.28), while the risk of hot flashes in postmenopausal and late perimenopausal women was not influenced by BMI.9
More recently, Whitman et al. reported that perimenopausal women with a BMI >30 kg/m2
were more likely to have any or daily hot flashes (OR, 2.1; 95% CI, 1.5 to 3.0) compared to women with a normal BMI. As in the two prior studies, the hot flashes of the postmenopausal women were not associated with BMI.10
In contrast to our findings, some studies have found an association between high BMI and fewer hot flashes,27
as well as below normal BMI and greater risk of hot flashes.14,28
Each of these studies included postmenopausal women only, while studies showing high BMI as a risk factor for hot flashes included both perimenopausal and postmenopausal women or perimenopausal women only.
The predominant form of estrogen in postmenopausal women is estrone, produced in adipose tissue by the conversion of androstenedione.29
This connection between adipose tissue and estrogen production has been used to explain outcomes of studies showing an increased risk of hot flashes in women with low BMI.14
However, studies evaluating the relationship between serum estrogen levels and hot flashes have shown that estrogen levels correlate poorly with hot flash activity.23
Estrogen is only one factor that may explain the association of BMI with hot flashes. Hypothalamic regulation of core body temperature may play a role in hot flash physiology30,31
and has been shown to be related to menopausal status.32
Serum androgen levels, shown to decrease as women transition to menopause33
and in women with elevated BMI,34
may also contribute to hot flash physiology.35,36
Despite a lack of consensus in the literature, the majority of studies demonstrate an association between elevated BMI and increased hot flashes. Moreover, this association appears to vary by menopausal status.
In our analysis, perimenopausal women who consumed 1 to 5 alcohol-containing drinks per week reported hot flashes less often than women who drank no alcohol. Alcohol use was not significantly associated with hot flashes in the postmenopausal women. Prior studies have reported an association between alcohol use and hot flashes. In 2001, Freeman et al. found that weekly alcohol use increased hot flashes in perimenopausal women (OR, 1.10; 95% CI, 1.03 to 1.17).8
Schwingl et al. found that postmenopausal women reporting ever drinking alcohol were more likely to have hot flashes than those who never drank; however, this trend was not statistically significant.14
One additional study of 11 postmenopausal women found that alcohol use increased the duration and intensity of hot flashes.13
Although a causative link between alcohol and hot flashes is not well established, multiple processes exist by which alcohol could impact hot flashes. Estrogen deficiency, measured in women reporting chronic, heavy alcohol use has been attributed to direct toxic effects of alcohol on the ovaries and liver.37
Mild to moderate alcohol use has also been shown to alter serum estrogen. In a randomized, controlled trial of postmenopausal women and alcohol use, women who drank 1 and 2 drinks per day for 8 weeks increased their serum estrone concentrations by 7.5% and 10.7%, respectively.38
Alcohol may also affect hypothalamic temperature regulation39
and serum androgen levels.38,40,41
Although the mechanism by which alcohol affects hot flashes is unclear, our study suggests that the intake of 1 to 5 alcohol-containing drinks per week may reduce a perimenopausal woman's risk of hot flashes.
Perimenopausal women in our study who reported daily multivitamin use had 56% higher odds of reporting hot flashes compared to women who did not take a multivitamin. This observation was of borderline statistical significance (). One possible explanation for the tenuous association between multivitamin use and hot flashes may be that symptomatic women used vitamins to try and treat their hot flashes. Supplements, such as vitamin E, are recommended in the literature as adjunctive therapy for hot flashes.21
However, one randomized, controlled trial in women with breast cancer found vitamin E to be only slightly better than placebo in reducing hot flashes.42
No studies to date have shown any increased risk for hot flashes with multivitamin use.
Women who take supplements tend to have characteristics typically associated with healthful behavior. Whether multivitamin use is simply a marker for another behavior that contributes to hot flashes cannot be discerned from these data.43,44
Given the likelihood that other confounding factors exist, our findings of a possible association between multivitamin use and hot flashes must be interpreted with caution.
We did not find a statistically significant association between exercise and hot flashes. In 1998, an analysis of postmenopausal women found that 5% of women reporting a high level of physical activity experienced hot flashes, compared to 14% to 16% of women with little or no weekly exercise (risk ratio [RR], 0.26; 95% CI, 0.10 to 0.71).18
In 2000, an analysis of women in the SWAN study found that women rating themselves as less physically active were more likely to report hot flashes (OR, 1.24 to 2.33).9
Other studies, including one randomized, controlled trial,17
have not found a significant association between exercise and hot flashes.45–47
Despite clinical guidelines supporting regular physical activity to reduce hot flashes,48
the association between exercise and hot flashes remains unclear and is not supported by our findings.
Intake of at least 1 high-fat meal per day compared to intake of high-fat food weekly or less was associated with fewer hot flashes in the postmenopausal women in our analysis. Dietary fat did not influence hot flashes in the perimenopausal women. We found no interaction between high-fat intake and BMI, and thus the effect of dietary fat on hot flashes appears to be independent of BMI. As with multivitamin use, dietary fat may be confounded by variables that we were unable to control for, such as the health status of women who reported very low-fat diets.
To our knowledge, the association of dietary fat and hot flashes has not been reported previously. Additional evaluation, using prospectively gathered data and validated food frequency questionnaires, should be performed to assess the possible association between dietary fat and hot flashes.
but not all13–15
studies on correlates of hot flashes note an association between smoking and an increased risk of hot flashes. We found smoking to be significantly correlated with hot flashes in perimenopausal women with depression. Smoking was associated with 2-fold increased odds of reporting bothersome hot flashes (OR, 2.19; 95% CI, 1.06 to 4.54). We used interaction terms to assess effect modification between smoking and all other variables in the perimenopausal model. When the only statistically significant interaction term, between smoking and depression, was entered into the model for perimenopausal women, smoking alone was no longer an independent correlate (OR, 0.64; 95% CI, 0.19 to 2.14). This suggests that depression modifies the effect of smoking on hot flashes in perimenopausal women, such that perimenopausal women with a history of depression who smoked at the time of the study were more likely to have hot flashes than nonsmokers with depression. Smoking did not affect the hot flashes of women in the postmenopausal group.
Various mechanisms may contribute to the anti-estrogenic effects of tobacco smoke.49
Smoking is thought to have direct toxic effects on the ovary,50
leading to menopause an average of 1.7 years earlier in women who smoke compared to nonsmokers.51
Oral estrogen metabolism is affected by smoking via upregulation of liver metabolism52
and estradiol clearance by hydroxylation.53
Smoking has also been shown to alter serum androgen levels, with variable effects by menopausal stage.54–56
Given the small number of smokers in our sample and the apparent effect modification of smoking by depression, the role of smoking in the development of hot flashes by menopausal stage requires further investigation.