Gender Modifies the Effects of Education and Income on Sleep Quality of the Patients with Coronary Artery Disease

BACKGROUND This study aimed to investigate the interaction between gender and other socio-economic characteristics on sleep quality of the patients with Coronary Artery Disease (CAD). METHODS This cross sectional study was conducted on 717 patients with CAD. The socio- economic status (education level, income, marital status, and place of residence) was considered as the independent variable. Besides, the study outcome was the quality of sleep which was measured using Pittsburgh Sleep Quality Index (PSQI). Gender was considered as a possible effect modifier. Two-way ANOVA was used to evaluate the interaction between gender and socio-economic factors on sleep quality. As defined by Baron and Kenny, moderator was defined as a variable that affected the direction or magnitude of the association of interest. RESULTS Female gender, low education level, and low income were predictive of poor sleep quality. Among female (10.0 ± 4.3 vs. 7.6 ± 5.0, P < 0.05), but not male patients (6.7 ± 4.2 vs. 7.0 ± 4.2, P > 0.05), low education was associated with poor sleep quality. Also, among female (10.0 ± 4.3 vs. 5.7 ± 2.5, P < 0.05), but not male patients (7.0 ± 4.2 vs. 6.0 ± 3.8, P > 0.05), low income was predictive of poor sleep quality. Gender did not modify the effect of other socio-economic factors on sleep quality. CONCLUSIONS Among female but not male patients with CAD, low education and income were associated with poor sleep quality. This information helps us better understand the mechanisms behind the poor sleep quality of the female patients with CAD. This is important because poor sleep is a prognostic factor among the CAD patients.