Study Identifies Sleep Length Associated With Lowest Mortality Rate in Patients With T2D

A study published in Cardiovascular Diabetology found that sleep duration was associated with risk of cardiovascular disease (CVD) mortality in participants with type 2 diabetes (T2D). The aim of the study was to examine the associations of baseline sleep duration with subsequent risks of all-cause, expanded CVD, and nonexpanded CVD mortality.

The retrospective cohort study took place at the Diabetes Care Management Program (DCMP) of China Medical University Hospital in Taiwan. Participants all had a diagnosis of T2D, and all enrollees in the DCMP registry between November 2001 and April 2016 were eligible for the study. Participants were excluded if they had gestational diabetes, were younger than 30 years, or had fewer than 3 years of follow-up. A total of 12,526 patients were included in the study.

All participants underwent medical tests for vital signs, blood, urine, anthropometric measurements, and lifestyle behaviors; medical history was also acquired. All measurements were recorded annually. Sleep duration was determined by a questionnaire; participants were asked to record their typical hours of sleep a month prior to the interview. Cutoff points for the 6 groups were: 4 or fewer hours of sleep, 5 to 6 hours, 7 hours, 8 hours, 9 to 10 hours, and greater than 10 hours.

All patients were followed up from index date in the DCMP to August 2021, date of withdrawal from the DCMP, or death.

There were 2918 patients who died during the mean (SD) follow-up of 10.82 (3.90) years, including 1328 expanded CVD deaths and 1590 non-expanded CVD deaths. Expanded CVD mortality was defined as death from CVD, diabetes, or kidney diseases, as defined by International Classification of Diseases codes, whereas nonexpanded CVD deaths were from only CVD.

Patients who slept for longer than 10 hours a day were more likely to be female, not alcohol drinkers, physically inactive, and older than 45 years at time of diabetes diagnosis and were more likely to have hypertension, higher chance of stroke, coronary artery disease, peripheral neuropathy, and cardiovascular medication use than patients who slept for 7 hours a day.

Patients who slept for longer than 10 hours a day also had lower mean body mass index (BMI) and estimated glomerular filtration rate values but higher mean age and diabetes duration than patients who slept for 7 hours a day. The proportions of participants with sleep durations of 4 or fewer hours, 5 to 6 hours, 7 hours, 8 hours, 9 to 10 hours, and greater than 10 hours were 1.64%, 16.04%, 26.15%, 29.32%, 23.23% and 3.62%, respectively.

A multivariate Cox regression model demonstrated that patients with sleep durations of 4 or fewer hours, 9 to 10 hours, and more than 10 hours had higher mortality risks than patients with a sleep duration of 7 hours (≤4 hours: HR, 1.41; 95% CI, 1.06-1.86; 9-10 hours: HR, 1.37; 95% CI, 1.23-1.52; >10 hours: HR, 1.82; 95% CI, 1.54-2.14).

Patients who slept for 4 or fewer hours, 9 to 10 hours, and more than 10 hours a day had higher risk of mortality from expanded CVD (≤4 hours: HR, 1.54; 95% CI, 1.04-2.28; 9-10 hours: HR, 1.34; 95% CI, 1.15-1.57; >10 hours: HR, 1.88; 95% CI, 1.49-2.37). Excess risks of nonexpanded CVD mortality were found in patients with sleep durations of 8 hours, 9 to 10 hours, and more than 10 hours (8 hours: HR, 1.16; 95% CI, 1.01-1.34; 9-10 hours: HR, 1.39; 95% CI, 1.20-1.60; >10 hours: HR, 1.77; 95% CI. 1.41-2.23).

When the analysis included patients younger than 30 years, patients with a sleep duration of 4 or fewer hours, 9 to 10 hours, and more than 10 hours had a higher risk of all-cause mortality and expanded CVD mortality than those with a sleep duration of 7 hours.

Adjusted HRs of sleep duration of more or less than 7 hours with age, diabetes duration, age at diabetes diagnosis, insulin use, and BMI were all significant for all-cause, expanded CVD, and nonexpanded CVD mortality. Significant interactions were found between sleep duration and obesity on all-cause mortality, sleep duration and age on expanded CVD mortality, and sleep duration and diabetes duration and obesity on nonexpanded CVD mortality.

There were some limitations to this study. Sleep measurement was reported by a questionnaire and not an objective measure, which means it lacks information on sleep quality and depression. Only 1.6% of the patients had a sleep time of 4 or fewer hours, so results should be taken with caution.

The researchers concluded that sleep duration is a predictor of all-cause, expanded CVD, and nonexpanded CVD mortality in patients with T2D, and those with a sleep duration of 5 to 7 hours are at lowest risk of mortality.

Reference

Li CI, Lin CC, Liu CS, Lin CH, Yang SY, Li TC. Sleep duration predicts subsequent long-term mortality in patients with type 2 diabetes: a large single-center cohort study. Cardiovasc Diabetol. 2022;21:60. doi:10.1186/s12933-022-01500-0