At 68 years, unrecognised sleep apnoea is associated with elevated ambulatory blood pressure

After the age of 65 yrs the specific impact of unrecognised sleep-related breathing disorders (SRBD) on 24-h blood pressure (BP) levels remains under debate. We tested the cross-sectional relationship between the severity of obstructive sleep apnoea/hypopnoea (OSAH) and the increase of BP using ambulatory BP monitoring (ABPM) in the PROOF (PROgnostic indicator OF cardiovascular and cerebrovascular events study)-SYNAPSE (Autonomic Nervous System Activity, Aging and Sleep Apnea/Hypopnea study) cohort. 470 subjects (aged 68 yrs) neither treated for hypertension nor diagnosed for SRBD were included. All subjects underwent ABPM, and unattended at-home polygraphic studies. OSAH was defined by an apnoea/hypopnoea index (AHI) >15 · h(-1). The severity of the sleep apnoea was also quantified as the index of dips in oxyhaemoglobin saturation >3% (ODI). Results are expressed in per protocol analysis. Severe OSAH (AHI >30 · h(-1), 17% of subjects) was associated with a significant 5 mmHg increase in both diurnal and nocturnal systolic BP (SBP), and with a nocturnal 3 mmHg increase in diastolic BP (DBP). Systolic (mean SBP >135 mmHg) or diastolic (mean DBP >80 mmHg) hypertension were more frequently encountered in subjects suffering from moderate (AHI 15-30) or severe OSAH. After adjustment, the independent association between severe OSAH and 24-h systolic hypertension remained significant (OR 2.42, 95% CI 1.1-5.4). The relationship was further reinforced when SRBD severity was expressed using ODI >10 · h(-1). The impact of unrecognised SRBD on BP levels also exists at the age of 68 yrs. The hypoxaemic load appears to be the pathophysiological cornerstone for such a relationship.