Objective Obstructive sleep apnea(OSA) induces marked hemodynamic fluctuations that might be deleterious to the cardiovascular system.The influence of OSA and aging on short-term blood pressure(BP) variability in OSA patients was investigated.The standard deviation(SD) and coefficient of variation(CV) of BP during daytime and nighttime were assessed to estimate short-term BP variability.Methods Totally 143 subjects with newly-diagnosed untreated OSA were categorized into three groups: subjects aged <60 years with untreated hypertension(n=62);normotensive subjects aged<60 years(n=38);and normotension subjects aged>60 years(n=43).Twenty four-hour BP was recorded after polysomnography.Results The SD of systolic or diastolic BP during daytime and nighttime was significantly greater in hypertensives than in normotensives aged<60 years(18.5 vs 10.6mmHg,P<0.05,and 13.8 vs 10.6mmHg,P<0.05,daytime;20.5 vs 12.6mmHg,P<0.01 and 17.8 vs 12.6mmHg,P<0.01,nighttime),as was the CV of systolic or diastolic BP during daytime and nighttime(0.119 vs 0.078,P<0.01 and 0.139 vs 0.118,P<0.05,daytime;0.137 vs 0.111,P<0.01 and 0.195 vs 0.177,P<0.01,nighttime);compared to the group of normotensive aged>60 years,the SD of systolic or diastolic BP variations during daytime and nighttime were higher in hypertensives(18.5 vs 13.3mmHg,P<0.05 and 13.8 vs 10.2mmHg,P<0.05,daytime;20.5 vs 15.2mmHg,P<0.01 and 17.8 vs 14.2mmHg,P<0.01,nighttime),and as was the CV of systolic BP during daytime(0.119 vs 0.093,P<0.05) and systolic or diastolic BP during nighttime(0.137 vs 0.123,P<0.01 and 0.195 vs 0.179,P<0.01).Daytime systolic BP CV was increased in normotensive elderly patients than in patients aged<60years(0.093 vs 0.078,P<0.05).As to the target organ damage,hypertensive group had higher rate than the two normotensive groups(P<0.05),and the elderly group had more target organ damage than the patients aged<60years(P<0.05).Conclusion Systemic hypertension is associated with a more severe exacerbation of short-term variability and higher rate of target organ damage in the OSA patients.