In this analytic cross-sectional study, women who were referred to three hospitals in Tehran (Rasool-e-Akram, Pars, and Nikan) between the years 2019–2022 were considered as the study population. Those who were diagnosed with endometriosis by clinical signs and symptoms and ultrasonic findings were enrolled into the case group and those without endometriosis in the control group.
A simple random sampling of odd serial reception numbers was used to select the control group at the same time. Inclusion criteria were women between 18 and 40 years old with a preliminary diagnosis of endometriosis, and willingness to participate in the study. Exclusion criteria were patients with previously known mental, neurologic, or sleep disorders who received treatment, participation rejection, patients under the age of 18 and over the age of 40, women with night shift work, and patients who used medications with impact on the sleep-wake cycle. In the first step, the researcher explained the study objectives (the frequency of sleep disorders) to the eligible patients and asked them to read and sign the written informed consent. Eligible women who gave consent for participation were enrolled in the study by census method. We tried to match the characteristics of the study groups as much as possible in important variables.
The minimum sample size of the study was calculated at 400 for the case group, considering the prevalence of sleep disorders in women with endometriosis at 63.8% (according to the study by Maggiore et al. [22]; considering type I error at 0.05 and type II error at 0.1, using the sample size calculation equation. For the control group, about half were considered for significant results.
The researcher collected the participants’ information, including demographics, ethnicity, age, body mass index (BMI), marital status, educational level, job status, as well as gynecology history of the participant, including gravidity, parity, infertility, and underlying diseases including uterine myoma, adenomyosis, etc. Also, endometriosis symptoms, including dysmenorrhea, dyspareunia, dysuria, pelvic pain, and dyschezia, were asked from the patients of the case group during history taking and recorded in the study’s checklist and the patients were asked to rank the severity of these symptoms using a 10-scale visual analog scale (VAS).
The participants were then placed in a quiet room with sufficient light and good air conditioning and asked to answer the questions of the Pittsburgh Sleep Quality Index (PSQI) questionnaire, designed by Buysse et al. in 1989 [23], which evaluates 7 components of the participant’s quality of sleep in the past month by 19 items, including “sleep duration, sleep disturbance, sleep latency, daytime dysfunction due to sleepiness, sleep efficiency, overall sleep quality, and sleep medication use.” The Persian version of this questionnaire has been used in this study and has been validated previously by Moghaddam and colleagues [24].
The total score was calculated by the sum of scores within the range of 0–21; lower scores indicate a better sleep quality. A score < 5 is suggested to discriminate good sleepers from poor sleepers with a sensitivity of 89.6% and specificity of 86.5% [23].
Ethical considerations
The protocol of the study was approved by the Ethics Committee of Iran University of Medical Sciences (code: IR.IUMS.REC.1396.31621). The study’s design and objectives were explained to all participants. Written informed consent was obtained from those willing to participate in the study and clarified that they were free to leave it whenever they wished.
Statistical analysis
We analyzed the data using the IBM SPSS Statistics version 27.0 (IBM et al., USA). A descriptive analysis was used to describe the general characteristics and study variables of the study population; mean ± standard deviation (SD) and median (interquartile range: IQR) were used for the numeric variables based on their distribution pattern and number (percentage) were used for the qualitative variables. The Mann-Whitney U test was used to compare the characteristics of the two groups, considering the non-normal distribution of the PSQI score and all its components. In addition to expressing the effect size (95% CI) of comparisons, Cohen’s d and Eta-squared were measured. The interpretation is to refer to Cohen’s d effect sizes as small (d = 0.2), medium (d = 0.5), and large (d = 0.8). Eta-squared effect size was used for the analysis of variance (ANOVA). 0.01 indicates a small effect, a medium effect = 0.06, and a large effect = 0.14. Linear multiple regression was performed using the Enter method to identify factors affecting sleep quality in the study groups, and another linear multiple regression for important factors in the case group; the global PSQI score was considered as the dependent variable, and other variables of the study including marital status, age, job, gravid, parity, BMI, infertility as independent variables in both groups and marital status, age, job, work, gravid, parity, BMI, infertility, dysmenorrhea, dyspareunia, dysuria, Pelvic pain, dyschezia, underlying diseases, hormonal, and surgical treatment as independent variables. P values under 0.05 were regarded as significant.
