ORLANDO – For patients with type 2 diabetes, larks may have an edge on owls when it comes to mood, according to a new study. Significantly more depressive symptoms were seen in owls – individuals whose sleep time preference, or chronotype, was later-to-bed and later-to-rise – in a cohort of 476 patients with type 2 diabetes.
In work that accounted for regional differences in chronotype by drawing from two different geographic regions, a later chronotype was associated with a higher score on the Center for Epidemiologic Studies Depression scale (CES-D), after controlling for potentially confounding factors (P = .045 for each cohort).
The study’s senior author, Sirimon Reutrakul, MD, of the faculty of medicine at Mahidol University, Bangkok, Thailand, said that previous work had also shown that when depression in patients with diabetes is untreated, self-care and blood glucose control can suffer, and more complications of diabetes are seen.
Dr. Reutrakul’s facility teamed with Rush University School of Medicine in Chicago, administering questionnaires designed to assess where patients fell along the morningness-eveningness scale. For the Chicago cohort (n = 194, 70% female), the Morningness-Eveningness Questionnaire (MEQ) was administered, while the Thailand cohort (n = 282, 57% female) completed the Composite Score of Morningness (CSM). Both groups completed the CES-D to assess depressive symptoms and the Pittsburgh Sleep Quality Index (PSQI); hemoglobin A1c values for both groups were ascertained by medical record review.
The mean age for the two cohorts was similar (Chicago, 58.3 plus or minus 13.0 years; Thailand, 55.7 plus or minus 11.6 years). The Chicago patients who scored higher on the CES-D, indicating that they had more depressive symptoms, were more likely to have a later chronotype on unadjusted analysis (P = .001). They were also likely to be younger (P = .005) and to have poorer sleep quality (P less than .001). Patients with more depressive symptoms were significantly more likely to be female, non-white, to use insulin, and to have poor glycemic control.
For the patients in Thailand, more depressive symptoms were also associated with a later chronotype on unadjusted analysis (P less than .001); younger age (P = .019), and poor sleep quality (P less than .001) were also associated with more depressive symptoms. Correction for a number of potentially confounding variables yielded modest statistical significance (P = .045) of the depressive symptoms-later chronotype relationship in both cohorts.
The Chicago patients were at approximately latitude 42N, while the patients in Thailand were at about latitude 13N, much closer to the equator. Populations that live closer to the equator, where days and nights are of approximately equal length year-round, tend to have more larks than owls, wrote Dr. Reutrakul and her colleagues.
In these two cohorts, which differed both by ethnic composition and geographic distance from the equator, “later chronotype was found to be independently associated with depressive symptoms” for patients with type 2 diabetes, wrote Dr. Reutrakul and her coauthors in the abstract accompanying the presentation. “In addition, sleep disturbances, more prevalent in evening types, have been associated with depression,” which is common in type 2 diabetes, the investigators wrote.
Dr. Reutrakul acknowledged that the work found an “only modest,” though consistent, association between eveningness and depressive symptoms. “We need further research to explore a combination of interventions that help with circadian timing, such as light therapy and melatonin,” she said in a press statement preceding her presentation. “Learning more about the relationship between depression and circadian functioning might help us figure out strategies to improve physical and mental health for patients with diabetes…We need further research to explore a combination of interventions that help with circadian timing, such as light therapy and melatonin,” Dr. Reutrakul said.
Dr. Reutrakul reported financial relationships with Medtronic Minimed, Novo Nordisk, Merck, and Sanofi.
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