Study design and participants
This study utilized the data originated from the cross-sectional, observational study, Estrogenic Regulation of Muscle Apoptosis (ERMA) that investigates how hormonal differences over menopausal stages affects the physiological and psychological functioning of middle-aged women. The study data collection proceeded in three phases described in detail in Kovanen et al.17 and in Figure 1. Briefly, written invitation was sent to 6878 randomly selected women aged 47 to 55 years living in Central Finland. The response rate was 46.9%. In total, 3064 women were willing to participate in ERMA Phase 1 and, in addition to written consent, they returned prequestionnaire which included questions on symptoms of pelvic floor disorders. Thereafter, the exclusion criteria included conditions or use of medications affecting ovarian function, obesity (self-reported body mass index [BMI] > 35 kg/m2), and chronic diseases or medications affecting muscle function. From the eligible participants (n=1627), 1393 gave fasting blood samples (Phase 2) and 1102 of them answered to the main questionnaire survey (Phase 3). The sample size of the present study is 1098, since four main questionnaires were lost due to technical error. The study protocol followed good clinical and scientific practice and the Declaration of Helsinki and was approved by the Ethics Committee of the Central Finland Health Care District (KSSHP Dnro 8U/2014).