It seems that articles on sleep apnea often report the correlational, not causal, relationship between sleep apnea and various conditions, including obesity. And yet, obesity itself can be a cause for stroke and cardiac issues. Do we have any conclusive proof that there is a causal relationship between sleep apnea and health and/or psychiatric issues?
Acta Clin Belg. 2013 May-Jun;68(3):169-78.
Cardiovascular mechanisms and consequences of obstructive sleep apnoea.
Vrints H1, Shivalkar B, Hilde H, Vanderveken OM, Hamans E, Van de Heyning P, De Backer W, Verbraecken J.
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Abstract
Obstructive sleep apnoea (OSA) is considered as a risk factor for the development of arterial hypertension, coronary artery disease (CAD), myocardial infarction and stroke. These clinical manifestations are the consequences of elevated sympathetic activity, cardiovascular variability, intrathoracic pressure changes, inflammation, oxidative stress, endothelial dysfunction, insulin resistance and thrombosis provoked by OSA. As a result, OSA is often present in patients with cardiovascular disease (CVD) and the increased prevalence of CVD in OSA population raises both cardiovascular morbidity and mortality and the demand of healthcare resources. Observational cohort studies indicate that untreated patients with OSA have an increased risk of fatal and non-fatal cardiovascular events, an increased risk of sudden cardiac death during the sleeping hours and a higher risk of stroke or death from any cause. Continuous positive airway pressure (CPAP) and oral appliance therapy are the two treatments for OSA whose effects on cardiovascular endpoints have been assessed in randomised trials. There is increasing evidence that adequate CPAP therapy leads to a significant reduction in cardiovascular morbidity.
Fadwa,
Thanks for the two articles. Related to my original question, it still seems as though there is circumstantial and correlative evidence connecting cardiac problems and cognitive abnormalities with sleep apnea, per the Usmani et al article you supplied: "OSA has been associated with an increased risk of cardiovascular disease, cognitive abnormalities and mental health problems. Randomised controlled trial evidence is awaited to confirm a causal relationship between OSA and these various disorders."
It does seem like a reasonable hypothesis that decreased oxygen flow to the body in patients with sleep apnea would increase the risk for such disorders,but increased risk is very far removed from causation. For example, one must compare such risks against the baseline risk for all these conditions simply as a function of age alone.
An example from the psychiatric world is the "black box" warning of increased risk of suicidal ideation in adolescents taking SSRI antidepressants. Yet the increased risk of suicidal ideation - not suicidal attempts - is very small and in the vast majority of cases treatment is much less risky than failing to treat the depression.
Among the innumerable articles that state an association, I have not found convincing evidence of a causal relationship, though there are several hypothesized mechanisms. At a major Sleep Medicine conference I attended a few years ago, one study was cited as showing OSA as directly causative of cardiovascular effects. I believe it was this one: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC507773/pdf/990106.pdf . However, the only cardiovascular consequence demonstrated was development of hypertension. Consequent events such as strokes and heart attacks were only inferred. If a patient has no hypertension and only mild to moderate OSA, should they still be considered at risk?
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