# Reported daytime sleepiness in relation to orthopnea, restless legs and nocturia in patients evaluated for suspected obstructive sleep apnea

## TL;DR

This study finds that daytime sleepiness in people suspected of having sleep apnea is more strongly linked to symptoms like restless legs and orthopnea than to the severity of sleep apnea itself.

## Contribution

The study identifies that OSA-related symptoms, not the apnea severity, are the main predictors of daytime sleepiness.

## Key findings

- Restless legs and orthopnea were the strongest predictors of daytime sleepiness and irritability.
- AHI (apnea severity) had weaker associations with sleepiness and driving drowsiness compared to reported symptoms.
- Nocturia and restless legs were more significant than AHI in predicting work performance and sleepiness.

## Abstract

The aim of the study is to explore the extent to which daytime sleepiness in patients with suspected Obstructive Sleep Apnea (OSA) was correlated with OSA itself and OSA-related comorbidities and symptoms.

1,305 consecutive patients undergoing OSA workup were included. They underwent standard respiratory polygraphy during sleep and completed a 19-item questionnaire about sleep-related symptoms and signs, as well as the Epworth Sleepiness Scale (ESS). Analyses were based on questionnaire responses and the Apnea–Hypopnea Index (AHI) results and were conducted using stepwise regression analysis.

Using the ESS as the dependent variable, the strongest associations were found with self-reported orthopnea (7%) and restless legs (2%). For daytime sleepiness, self-reported restless legs accounted for 7,6% of the variance, followed by reported orthopnea (3.8%). Regarding daytime irritability, self-reported restless legs accounted for 7.7%, followed by age (4.4%), reported orthopnea (3%), and nocturia (1%) as significant factors. Reported likelihood of falling asleep while driving was best associated with the severity of self-reported restless legs (1,3%), orthopnea (0.6%), and patient age (0.4%). For work performance, restless legs were the strongest predictor (5.9%), followed by age (3.6%) and orthopnea (3%). AHI emerged as a significant explanatory factor regarding ESS score (1.7%) and falling asleep as driver (0.4%) when analyzing the above-mentioned variables.

Daytime sleepiness-associated symptoms were more strongly correlated with reported levels of restless legs, nocturia, and orthopnea than with the AHI score. If restless legs, orthopnea, or nocturia are present, they should be evaluated during the clinical workup for suspected OSA.

The online version contains supplementary material available at 10.1007/s11325-025-03312-4.