Night sweats were independently associated with a higher hypoxemia burden in patients diagnosed with obstructive sleep apnea (OSA).
The prevalence of night sweats in adults is between 10% and 41%, which can be caused by medical conditions, including OSA. Previous research has found that approximately 30% of patients with OSA report having night sweats. The researchers sought to assess the relationship between indicators of hpoxemia and patient-reported night sweats.
The study included patients who underwent a polysomnography (PSG) and completed a sleep questionnaire at Hospital Aleman in Buenos Aires between January 2017 and January 2020. Patients were excluded if they did not complete the questionnaire, underwent PSG for positive pressure titration, were receiving oxygen therapy, or had less than 10% artifact in the oximetry.
PSGs were conducted from 10:30 to 11:30 pm and 5:00 to 6:00 pm. Pulse oximetry was conducted with a Nonin oximeter and a finger clip sensor. Prior to the PSG, patients completed a sleep questionnaire and the Epworth Sleepiness Scale. Comorbidities were self-reported.
There were 1397 patients who were included in the study. The median age of the group was 52 years, 41.4% were women, 80% had OSA, and 35% were obese. Prevalence of night sweats was higher in patients with OSA compared with controls (18.9% vs 12.2%).
Patients with night sweats frequently reported excessive daytime sleepiness (EDS), awakenings or frequent body movements during sleep, nocturia or waking up to urinate more than once in the night, nightmares, and cardiovascular disease. These patients also had a higher body mass index (BMI), apnea hypopnea index (AHI) score, and hypoxemia, which was defined as the percentage of time with saturation below 90% (T90%) ≥ 2.5% of total recording time.
A logistic regression analysis determined that variables associated with night sweats were BMI, AHI, hypoxemia, awakenings or frequent body movements during sleep, nightmares, EDS, nocturia, cardiovascular events, and the use of sedatives or antidepressants. A multivariate model found that independent predictors of night sweats included hypoxemia, nightmares, awakenings or frequent body movements during sleep, and EDS.
According to the authors, the most important predictor of night sweats was frequent nightmares. They also explained that "Frequent awakenings during sleep and accompanying movements increase sympathetic tone and eventually lead to more sweating."
There were limitations to this study. Recall bias and lack of control for confounding variables is possible due to the retrospective and cross-sectional design of the study. Sweating was not objectively measured. A cause-effect relationship cannot be implied between oxygen desaturation and night sweats. Some clinical situations were not considered confounders of thist study, including chronic pain, chronic inflammatory disease, anxiety-depression disorders, and NREM parasomnia that have been associated with night sweats.
The researchers concluded that night sweats were significantly and independently associated with a higher hypoxemic burden for patients diagnosed with OSA.
"Patients with [night sweats] usually visit primary care physicians or other professionals who are not sleep medicine experts," they wrote. "Considering they are key to initiating a diagnostic investigation, it is important to update their knowledge on the prevalence of sleep respiratory disorders and the role of hypoxemia as a trigger for night sweats in OSA."
Nigro CA, Bledel I, Borsini E. Independent association between hypoxemia and night sweats in obstructive sleep apnea. Sleep Breath. Published online August 31, 2022. doi:10.1007/s11325-022-02701-3