Background: Hospital-associated sleep loss and poor overall sleep efficiency are associated with poor glycemic control and exacerbated insulin resistance. in diabetic patients. The relationship between sleep, sleep hygiene, and diabetes is confounded by social determinants of health, such as health literacy. The evaluation of insomnia often utilizes complex sleep diaries or logs that may not correlate well with objective measures such as actigraphy, particularly among patients with lower health literacy. Additionally, other literature has demonstrated positive associations between health literacy and care outcomes such as length of stay (LOS). Given the lack of data on health literacy and sleep quality and an increasing focus on reducing hospital readmissions, we sought to evaluate whether perceived sleep quality is associated with health literacy level. We also examined the effect of poor subjective sleep quality on LOS when stratified by health literacy level.

Methods: Through a retrospective, observational study, the research team explored a database of 721 hospitalized adult diabetic patients. The database contained objective measures of sleep efficiency and duration, such as sleep actigraphy. Subjective measures of sleep quality, including the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and Sleep Self-efficacy scale, were also assessed. Health literacy was captured using the Brief Health Literacy Screen (BHLS). Length of Stay was calculated based on index admission and discharge. Associations between sleep quality with subjective indices and health literacy were assessed via t-test, chi-square, and logistic regression (where subjective indices were treated as ordinal variables). Stratified analysis was conducted using multivariable regression.

Results: Among 721 hospitalized patients, 21% had low health literacy (151). Subjects with low HL had a lower average ordinal PSQI score (moderate sleep difficulty, score range 8-14), P = 0.03. Low HL was not associated with low ESS (p = 0.12). Sleep self-efficacy score was also not significantly associated with health literacy (p = 0.56). Multivariate analysis revealed that aggregate subjective sleep indices were not associated with a significant increase in LOS (95% confidence interval [CI], 1.6%-8.4%; P = 0.23), However, this was significantly affected by health literacy (p=0.04). Binary aggregate subjective sleep quality was associated with an 8.6% longer LOS in subjects with low health literacy (95% CI, 6.6%-10.6%; P = 0.02). All analysis was conducted on SPSS statistical software.

Conclusions: Aggregate sleep quality was positively associated with LOS when stratified by health literacy. Additionally, health literacy was positively associated with PSQI scores. This suggests that inadequate health literacy may limit the interpretation of subjective sleep quality assessments. Moreover, this data is consistent with the findings that health literacy may be a risk factor for poor patient outcomes. Given the retrospective nature of this study, it is subject to several limitations, including biases in recall or misclassification. The binary stratification of health literacy and aggregate sleep quality data may have also resulted in inaccuracies in association. Finally, confounding by unaccounted variables may have affected the outcomes of the analysis.