| Description |
Background: As the field of sleep research grows, the correlation between inadequate sleep duration and debilitating health conditions becomes more apparent. While the majority of research in this field has focused on sleep duration, recent findings have also stressed the importance of sleep regularity, especially in relation to the risk of chronic diseases, including diabetes. Methods: We investigated the impact of a sleep extension intervention on sleep regularity and insulin sensitivity in adults with habitual short sleep duration (n=12). Participants in the Restoring Adequate Sleep Duration (RADS) study received interventions that aimed to increase their nightly sleep duration for four weeks. Participants' insulin sensitivity (Matsuda Index) was measured by an oral glucose tolerance test, taken at both the baseline and post-intervention visits. Sleep regularity was determined by the Sleep Regularity Index (SRI) from wrist actigraphy data collected throughout the study. Findings: Total Sleep Time was 5.3 ±0.2 hours (mean ±SEM) at baseline and significantly increased 69.6 ± 10.32 minutes (mean ±SEM) during sleep extension. Matsuda Index was 5.96 ±0.64 (mean ±SEM) at baseline and significantly decreased 0.83 ± 0.3667 (mean ±SEM) after sleep extension. SRI was 75.8 ± 2.3 (mean ±SEM) at baseline and did not significantly change during after sleep extension. Interpretation: Our original hypothesis predicted an increase in SRI, and a subsequent increase in Matsuda Index Values, as Total Sleep Time increased. Yet, preliminary analysis showed no change in SRI, a decrease in Matsuda Index, and an increase in Total Sleep Time. These findings show the sleep extension intervention successfully increased Total Sleep Time without altering sleep regularity, suggesting Total Sleep Time and sleep regularity are potentially independent dimensions of sleep health. Moreover, it is possible that the change to participants' typical sleep-wake schedule caused an adverse shift in circadian rhythm that is underlying the negative changes in insulin sensitivity. These findings indicate interventions other than simple sleep extension may be required to improve sleep regularity and insulin sensitivity. |
