Obesity Screening to Predict Hot Flashes
Vasomotor symptoms (VMS) include hot flashes and night sweats. They are the primary symptoms of menopause and affect 60-80% of women. These symptoms all lead to a reduction in the quality of life.
Contrary to the previous belief that VMS occurs near the final menstrual period and is short-lived, new studies show that VMS is commonly observed in the premenopausal and early menopausal transition stages and may persist long after menopause. Early-onset and long duration of VMS were linked with adverse psychosocial and physical profiles and increased risk of subclinical and cardiovascular disease. Despite their impact on the quality of life and risk profile of women, few studies have evaluated the distinctive characteristics of early-onset VMS.
Both obesity and overweight status are linked with VMS. It’s also believed that weight loss may reduce VMS. These findings support the notion that obesity is a risk factor for VMS. Obesity is frequently accompanied by metabolic abnormalities such as type 2 diabetes, hypertension, dyslipidemia, and insulin resistance, but a subset of obese individuals do not present metabolic abnormalities despite having excessive body fat, a phenomenon referred to as metabolically healthy obesity.
No study has explored the role of metabolically healthy obesity on VMS risk. This study’s goal is to test the hypothesis that metabolically healthy and unhealthy obesity phenotypes affect VMS differently using cross-sectional and longitudinal studies of premenopausal women.
Study Population
The study is comprised of premenopausal Korean women aged 42–52 years. They were recruited and were followed up for a median of 4.2 years. The cross-sectional and cohort studies comprised a total of 4672 women and 2590 women without VMS at baseline, respectively.
Participants were recruited between 2014 and 2018 from the Kanbuk Samsung Health Study, a cohort study of Korean adults who received annual or biennial comprehensive health examinations at the clinics of Kangbuk Samsung Hospital Total Healthcare Centres in Seoul and Suwon, South Korea.
At baseline and at each follow-up visit, the researchers used the Korean version of the Menopause-Specific Quality of Life questionnaire to assess the presence and bothersome degree of VMS, including hot flashes and night sweats.
If the participant responded ‘No’ to hot flashes or night sweats, she was considered as not having VMS. If the participant responded ‘Yes’ and experienced hot flashes or night sweats and rated them on the bothered scale, she was considered as having VMS. Prevalent VMS was defined as VMS present at baseline, whereas incident VMS was defined as the new onset of VMS during follow-up among participants free of VMS at baseline.
Eligibility Criteria
The eligibility criteria for the study include (1) age 42–52 years; (2) no history of hysterectomy, oophorectomy, or hormone replacement therapy; (3) at least one menstrual period in the 3 months before the health screening examination and no amenorrhea lasting for 60 days or more; and (4) no history of a chronic disease that may affect menstrual cycles (malignancy, renal failure, and hypo- or hyperthyroidism). For the cross-section study, exclusion criteria included study withdrawal and missing information on VMS or adiposity measures or metabolic components Next, the exclusion criteria for the cohort study were (1) prevalent VMS at baseline (either hot flashes or night sweats or both); (2) no follow-up; and (3) missing information on VMS.
Metabolically healthy and unhealthy obesity
Body mass index (BMI) was categorized according to Asian-specific criteria as underweight (BMI <18.5 kg/m2), normal weight (BMI 18.5–22.9 kg/m2), overweight (BMI 23–24.9 kg/m2), obesity I (BMI 25–29.9 kg/m2) and obesity II (BMI ≥30 kg/m2).
Only a small proportion (5.3%) of study participants were categorized as underweight and they were combined into the normal weight category. The proportion of obesity II (BMI ≥30 kg/m2) was less than 2% and obesity I and II were combined into a single obesity category. Abdominal obesity was defined as a waist circumference of 80 cm or more, also a specific criterion for the Asian population.20 Percentage body fat was categorized as less than 25.0%, 25.0%–29.9%, 30.0%–34.9% and 35.0% or more.
Metabolically unhealthy persons were defined as those having at least one of the following metabolic abnormalities: fasting glucose level 100 mg/dL or more or current use of glucose-lowering agents; BP at least 130/85 mmHg or current use of BP-lowering agents; triglyceride level at least 150 mg/dL or current use of lipid-lowering agents; high-density lipoprotein cholesterol level less than 50 mg/dL; or insulin resistance, defined as a homeostatic model assessment of insulin resistance score at least 2.5. Being metabolically healthy was defined as having none of the metabolic abnormalities described above.
Previous studies and a meta-analysis have demonstrated that obesity is associated with an increased risk of VMS. Although the role of obesity in VMS is well documented, the association of obesity phenotypes based on metabolic health status and body composition with VMS has not been investigated in detail.
Women with higher adiposity show higher estrogen concentrations than lean women, which could potentially counteract the effect of estrogen deficiency during perimenopause and therefore lower the likelihood of VMS. However, we found that obesity phenotypes as defined by BMI, waist circumference, and percentage of body fat were associated with incident VMS, which is in line with recent studies.
Several studies reported that women with metabolic abnormalities had a higher risk of prevalent VMS than those without, but these studies did not specifically incorporate obesity phenotypes based on metabolic health, making it difficult to understand the role of obesity per se with or without metabolic abnormalities on VMS.
Results
All adiposity measures were positively associated with an increased risk of VMS in both cross-sectional and longitudinal studies. The multivariable-adjusted prevalence ratio (95% confidence interval [CI]) for VMS comparing the percentage of body fat of 35% or more with the reference was 1.47 (95% CI 1.14–1.90) in metabolically healthy women, and the corresponding prevalence ratio was 2.32 (95% CI 1.42–3.78) in metabolically unhealthy women (P interaction = 0.334).
The multivariable-adjusted hazard ratio for incident VMS comparing the percentage of body fat of 35% or more with the reference was 1.34 (95% CI 1.00–1.79) in metabolically healthy women, whereas the corresponding hazard ratio was 3.61 (95% CI 1.81–7.20) in metabolically unhealthy women (Pinteraction = 0.036). The association between BMI, waist circumference, and VMS did not significantly differ by metabolic health status.
Conclusion
To prevent hot flashes, night sweats, and all VMS in premenopausal women, it’s important to maintain a normal weight and strive to be metabolically healthy. In this cross-sectional and longitudinal analysis of midlife Korean women, BMI, waist circumference, and percentage of body fat were associated with an increased risk of VMS in premenopausal women. In the cross-sectional analysis, the researchers observed a positive association between obesity, abdominal obesity, percentage of body fat, and VMS prevalence in both metabolically healthy and unhealthy women with no significant interaction by metabolic health status. In the cohort analysis, the association of percentage body fat with incident VMS was stronger in the metabolically unhealthy group with significant interaction by metabolic status.
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