Central Sleep Apnea 383
nea should receive that diagnosis, even in th e presence of concurrent substance use that is
exacerbating the condition.
Comorbidity
Systemic hypertension, coronary artery disease, heart failure, stroke, diabetes, and increased
mortality are consistently asso ciated with obstructive slee p apnea hypopnea. Risk esti-
mates vary from 30% to as much as 300% for moderate to severe obstructive sleep apnea
hypopnea. Evidence of pulmonary hypertensi on and right heart fa ilure (e.g., cor pulmo-
nale, ankle edema, hepatic congestion) are ra re in obstructive sleep apnea hypopnea and
when present indicate either very severe di sease or associated hypoventilation or cardio-
pulmonary comorbidities. Obstructive sleep apnea hypopnea also may occur with in-
creased frequency in association with a number of medical or neurological conditions (e.g.,
cerebrovascular disease, Parkinson’s disease). Physical findings refl ect the co-occurrence of
these conditions.
As many as one-third of individuals referred  for evaluation of obstructive sleep apnea
hypopnea report symptoms of depression, with  as many of 10% having depression scores
consistent with moderate to severe depressi on. Severity of obstructive sleep apnea hypop-
nea, as measured by the apnea hypopnea index,  has been found to be correlated with se-
verity of symptoms of depression. This a ssociation may be stronger in males than in
females.
Relationship to Internat ional Classification of 
Sleep Disorders
The International Classification of Sleep Disorders,  2nd Edition (ICSD-2), differentiates 11 sub-
types of “sleep-related breath ing disorders,” including primary central sleep apnea, ob-