Introduction: Perimenopause also known as menopausal transition is the period of a woman’s life preceding the occurrence of menopause. During the menopausal transition stage, increased hot flushes and night sweats are the most frequently reported symptoms. In premenopausal women, cyclic changes in plasma and sweat Na+ concentrations (but not K+) corresponding with hormonal fluctuations during the menstrual cycle have been documented.
Objective: To investigate the relationship between rate of sweat production and sweat potassium concentration in premenopausal (PreM), perimenopausal (PeriM) and postmenopausal (PostM) women after a moderate exercise.
Study Design: This is a cross-sectional study conducted in May 2012 at the Department of Physiology, University of Benin, Nigeria.
Methods: Thirty healthy female volunteers comprising of PreM (aged: 22.5±0.8 yrs, n = 10), PeriM (aged: 46.5±1.1 yrs, n = 10), and PostM (aged: 52.2±0.9 yrs, n = 10) participated in the study. Sweat was obtained with a sweat suction apparatus from a 120 cm2 circular area marked on the skin of the face and neck after a 15 min walk on a calibrated treadmill at a speed of 4.2 km/h at 27°C and a relative humidity of 85-95%, followed by measurement of sweat volume (SV) and [K+]. Sweat rate (SR) was determined by dividing the volume of sweat produced by the duration of exercise. Thirst perception (TP) was self-rated using the Visual Analogue Scale (VAS).
Results: The PeriM women demonstrated higher SR (ml/min) (P = 0.01) and SV (ml) (P = 0.0006) compared to women in the other groups: SR (PeriM = 0.12±0.01; PreM = 0.07±0.02; PostM = 0.06±0.01), and SV (PeriM = 1.7±0.2; PostM = 0.9±0. 1). However, they had lower sweat [K+] (mmol/l) (P = 0.04), compared to their PostM counterparts (PeriM = 19.98±1.5; PostM = 24.90±1.8). Furthermore, sweat [K+] was inversely associated with SR (r = -0.4, P = 0.02); and change in TP (cm) was highest (P = 0.001) in the PeriM women (PeriM = 2.5±0.2; PreM = 2.1±0.3; PostM = 0.99±0.2).
Conclusion: Although excessive sweating can lead to depletion of the body’s potassium concentration, the sweat potassium concentration decreases with increased sweating especially in perimenopausal women. This data indicate that sweat potassium concentration decreases with increased sweating in middle-aged women, and perimenopausal women excrete higher volumes of hypotonic sweat compared to pre – and postmenopausal women. This warrants further investigation, as it could be an adaptive mechanism inhibiting excessive potassium loss.
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