Association Between Obesity and Sleep Disorders in Postmenopausal Women

Maria Fernanda Naufel, MSc; Cristina Frange, MSc; Monica Levy Andersen, PhD; Manoel João Batista Castello Girão, MD, PhD; Sergio Tufik, MD, PhD; Eliane Beraldi Ribeiro, PhD; Helena Hachul, MD, PhD

Disclosures

Menopause. 2018;25(2):139-144. 

In This Article

Methods

The study was designed according to STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines and was approved by the Ethics Committee of the Universidade Federal de São Paulo (CEP #834146/2014). It was conducted in accordance with the Declaration of Helsinki.

Study Design and Study Population

One hundred seven postmenopausal volunteers from the Ambulatory of Integrative Treatment for Female Sleep Disorders were invited by telephone to participate in this study. We included women aged 50 to 70 years (n = 84) and exclusion was based on the use of hormone therapy (n = 8) and missing data (n = 23). Fifty-three completed the study. The study consisted of two meetings. Menopause status was confirmed by a history of amenorrhea for at least 1 year and with a medical appointment. All participants gave written consent and this authorized us to collect and use data from the meeting and from their medical records. PSG data were collected from their medical history.

Anthropometric Measurements and Form

Participants completed a form including age, use of hormone therapy, and presence of previous diseases such as diabetes, hypertension, and social data. Participants were allocated into two groups, according to body mass index (BMI): nonobese group (BMI <30 kg/m2) and obese group (BMI ≥30 kg/m2).

All measurements were taken by a trained technician and included body weight (kg), height (m), BMI (weight/height[2]), waist circumference (WC, cm), hip circumference (HC, cm), waist-to-hip ratio (WHR), and neck circumference (NC, cm).

Polysomnography

All full-night basal PSG data were collected in our laboratory (Sleep Institute, São Paulo, Brazil; www.sono.org.br) between January 2014 and July 2016. PSG was performed using a digital system (EMBLA S7000, Embla Systems Inc., Broomfield, CO) during their usual sleep time. The following physiological variables were assessed: electroencephalogram (EEG, F4-M1, C4-M1, O2-M1, F3-M2, C3-M2, O1-M2); electrooculogram (EOG, bilateral); electromyogram (EMG, muscle of the mentonian and submentonian, chin region and tibialis anterior muscle, bilateral); electrocardiography (ECG, derivation D2 modified); airflow detection by a thermocouple and by nasal pressure; respiratory effort using thoracic and abdominal x-trace belts; snoring and body position by EMBLA sensors; and percutaneous oxygen saturation (SpO2) and pulse rate by an EMBLA oximeter. A registered and trained PSG technologist visually scored all PSG. All sleep stages were scored according to standardized criteria for investigating sleep.[23] EEG arousals, leg movements, and respiratory events were scored according to the guidelines provided by the American Academy of Sleep Medicine.[23]

The PSG variables studied (and their ideal values[24]) were: sleep latency (time to initially fall asleep: normally under 30 minutes); total sleep time (TST) (variable within person); sleep efficiency (ratio of total sleep time to the total amount of time spent in bed, greater than 85% of TST); stages N1 (up to 5% of TST); N2 (45-55% of TST); N3 or slow wave sleep (up to 23% of TST); REM sleep (20%-25% of TST); REM sleep latency (LREM) (minutes after sleep onset to enter REM sleep stage); wake after sleep onset (WASO) (time spent awake during the sleep period time); apnea-hypopnea index (AHI) (normal index is under five events per hour and defined as the mean number of obstructive apneas and hypopneas per hour of sleep); and respiratory disturbance index (RDI) that reports on respiratory events during sleep.[23]

Statistical Analysis

Statistical analysis was performed using SPSS version 18.0 (IBM, Armonk, NY). The Shapiro-Wilk normality test was applied to determine data distribution. Parametric variables are presented as mean ± standard error and were compared by the Student's t test. Nonparametric is a non-normal distribution that warrants a comparison test that does not assume normality, and the nonparametric variables are presented as median (minimum-maximum) and were compared by the Mann-Whitney test. It compares median scores of two samples, being more robust against outliers and heavy tail distributions. The "U" is the test statistic for Mann-Whitney U test. Qualitative variables were compared using the chi-square or Fisher's exact tests. Pearson's correlation coefficient was used to describe the relationships between PSG variables and anthropometric measures. Multivariate regression analysis was performed to assess anthropometric factors influencing PSG variables after correlation analysis demonstrated the variables that were correlated and were adjusted for neck circumference and hip circumference. The regression models were constructed based on the significant correlations shown by the univariate analysis. Sample size was calculated for a statistical power of 0.85, an effect size of 0.28 (for alpha level of 0.05 with four predictors). A total of 53 volunteers was the required sample size. Statistical significance was considered at a level of P < 0.05.

Ethical Approval and Informed Consent

The study had the approval of the Ethics Committee of the Universidade Federal de São Paulo (CEP #834146/2014). Written informed consent was obtained from all participants.

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