Self-reported diurnal preference and sleep disturbance in type 2 diabetes mellitus

Background. Previous sleep studies suggest that type 2 diabetes mellitus is associated with poor quality of sleep and sleep disorders. Aim. To evaluate sleep parameters and diurnal preference in type 2 diabetic patients, using a questionnaire. Methods. Ninety seven patients (aged 55.8±8.3, sex ratio 1:1), previously diagnosed with type 2 diabetes mellitus, together with 102 controls (aged 47.1±10.5, sex ratio 1:1), without diabetes, completed a questionnaire containing the Romanian translation of the Composite Scale of Morningness, the Sleep Disorders Questionnaire, the Pittsburgh Sleep Quality Index, the Pittsburgh Insomnia Rating Scale, the Multidimensional Fatigue Inventory, the Epworth Sleepiness Scale, the Alcohol Use Disorders Identification Test and the Beck Depression Inventory II (BDI). The study was cross-sectional, as we included subjects from outpatient and inpatient facilities. The recruitment process was based on handing invitation letters to patients consulting their physician, as well as to their acquaintances, using the snowball sampling. Participation was voluntary and anonymous. Results. Insomnia was more often reported in diabetic patients: 32 (33.0%) vs. 16 (15.7%) controls, a difference that was highly significant (P<0.001). Diabetic patients used to wake up at approximately the same hour as controls did; nevertheless they went to bed earlier (22:14 ± 0:57 vs. 22:32 ± 1:03), needed more minutes to fall asleep (28.84 ± 21.01 vs. 24.32 ± 23.45) and slept less than controls (7.01 ± 1.56 vs. 7.23 ± 1.18). Statistically significant differences between patients and controls were found regarding the Pittsburgh Sleep Quality Index (P=0.005), the Pittsburgh Insomnia Rating Scale (P<0.001) and the Multidimensional Fatigue Inventory (P=0.001) scores. Eighteen (18.5%) patients also met the criteria for a depressive disorder. No significant differences between patients and controls were found as related to their chronotype (P=0.32) Conclusion. Poor sleep, but not diurnal preference, was linked with the presence of type 2 diabetes mellitus.