0494 Obstructive Sleep Apnea is Associated with Sympathetic Overactivation and Hypertension: Age Effect

Abstract Introduction The association between obstructive sleep apnea (OSA) and hypertension has been noted to be stronger in young and middle-aged than older adults. Since the sympathetic overactivation is a known mechanism of hypertension, we hypothesized that the association between OSA and sympathetic overactivation was moderated by age. Methods We recruited 166 consecutive patients with OSA from the sleep clinic of Shantou University Medical College. OSA was defined as an apnea-hypopnea index (AHI) ≥5 events/hour based on an overnight polysomnography. AHI and time under 90% oxygen (T90) were used to assess the severity of OSA and hypoxic burden. Twenty-four-hour urinary norepinephrine was used for assessing sympathetic activity. Blood pressure was averaged from morning and evening measurements. The older adults were defined as age50 years (the 75th percentile of the overall subjects). Results Among the 166 OSA patients, each 10-event/hour increase in AHI and 1-hour increase in T90 were associated with 1.63-μg (p=0.087) and 4.76-μg (p 0.001) increase in 24-hour urinary norepinephrine respectively after controlling for potential confounders. Furthermore, we found each 10-event/hour increase in AHI and 1-hour increase in T90 were associated with 2.59-μg (95%CI=0.43~4.75, β=0.22, p=0.019, interaction-p=0.075) and 6.36-μg (95%CI=3.41~9.31, β=0.37, p 0.001, interaction-p=0.017) increase in 24-hour urinary norepinephrine respectively among the young and middle-aged OSA patients, but not in the older patients (p=0.187 and 0.791) . Similarly, either AHI or T90 was associated with higher blood pressure among young and middle-aged (all p 0.001), but not in older patients (all p≥0.233). These associations were mediated by the levels of 24-hour urinary norepinephrine with mediation effect of 7.67~13.41% only among the young and middle-aged OSA patients. Conclusion OSA is associated with higher sympathetic activity and blood pressure in young and middle-aged, but not in older adults. Early prevention and intervention for OSA is essential to improve cardiovascular outcomes. Support (if any)