In this historical cohort study, 10,701 consecutive adults undergoing their first diagnostic polysomnogram between July 1987 and July 2003 were included. During follow-up up to 15 years, incident resuscitated or fatal sudden cardiac death (SCD) was assessed in relation to the presence of OSA, physiological data including the apnea-hypopnea index (AHI), and nocturnal oxygen saturation (O2sat) parameters.Authors found that, during an average follow-up of 5.3 years, 142 patients had resuscitated or fatal SCD (annual rate 0.27%). A multivariate analysis was performed and independent risk factors for SCD were found to be age, hypertension, coronary artery disease, cardiomyopathy or heart failure, ventricular ectopy or non-sustained ventricular tachycardia, and lowest nocturnal O2sat (per 10% decrease, hazard ratio [HR]:1.14;p=0.029). SCD was best predicted by age >60 years (HR:5.53), followed by nocturnal O2sat <93% (HR:2.93), and lowest nocturnal O2sat <78% (HR:2.60) and apnea-hypopnea index >20 (HR:1.60, all p<0.0001).
Comments. In this large population based study, OSA diagnosis independently predicted incident SCD. The authors correlated increasing risk of SCD with the severity of OSA (AHI>20) and the severity of nocturnal hypoxemia, indicating good biological plausibility. It was however difficult to determine how well the patients were treated with therapy such as CPAP during the follow-up period.
A study 139 low income women with HIV found that after controlling for HIV viral load, length of time with HIV, HAART adherence, perceived stress and depression, greater sleep disturbance, by self-report, was associated with lower CD4 count and lower levels of dopamine. Poorer overall sleep quality, measured by PSQI, was marginally associated with CD4 count.
Self-reported sleep and plasma cytokines were obtained in a cohort of depressed and non-depressed pregnant women at 20 and 30 weeks gestation. Among depressed women, short sleep duration was associated with higher IL-8, while poor sleep continuity was associated with higher IL-6. Higher IFN-gamma was associated with increase risk of pre-term birth in depressed women.
In a randomized cross-over design, 21 healthy normal weight males underwent 3 consecutive nights of sleep restriction (4 hr/night) and long sleep (9 hr/night). Pre– and post-prandial glucose, insulin and other metabolic markers were obtained. Fasting insulin, fasting C-peptide and post-prandial C-peptide were higher in sleep restriction condition than long sleep. HOMA-IR was also higher under sleep restriction.
Non-diabetic, overweight/obese participants who were insulin-resistant or insulin-sensitive underwent an oral glucose tolerance test. Individuals reporting short habitual sleep duration (<7 hours/night) were more likely to be insulin-resistant than insulin-sensitive.
These studies imply that sleep fragmentation, a frequent occurrence in many disorders and more specifically in sleep apnea, is a potent inducer of insulin resistance via activation of oxidative stress and inflammatory pathways.
This study “raises the possibility that patients with obstructive sleep apnea may be susceptible to atherosclerotic disease in the pulmonary vasculature”.
This study shows that prolonged sleep disruption of mice exacerbates febrile responses to lipopolysaccharide. This device provides a method to determine mechanisms by which chronic insufficient sleep contributes to the etiology of many pathologies, particularly those with an inflammatory component.
In a commentary published in the journal Critical Care, Folke Sjober and Eva Svanborg point on the importance of Dr. Elliot’s article which we reviewed in the May 2013 newsletter entitled “Characterization of sleep in intensive care using 24-hour polysomnography: an observational study”. Specifically, the authors point out the importance of studying sleep in the ICU with regards to understanding oxidative stress, immune function and subjective health. They applaud the authors for using polysomnography in such a large sample of ICU patients. However, Solberg and Svanborg admit we are only at the “tip of the iceberg” with regards to our understanding of the importance of sleep in the ICU and how to best study it.
Clinicians should consider evaluating and treating obstructive sleep-disordered breathing in children with severe or difficult-to-control asthma.