Objective To investigate the effect of obstructive sleep apnea syndrome (OSAS) on nocturnal ambulatory blood pressure monitoring results in older adults without cardiovascular or cerebrovascular diseases, and to identify factors causing fluctuations in nocturnal blood pressure in older adults with OSAS.

Methods A total of 169 older adult OSAS patients with no history of cardiovascular or cerebrovascular diseases were enrolled. According to their severity of OSAS, the participants were divided into 4 groups, including a normal OSAS group, a mild OSAS group, a moderate OSAS group, and a severe OSAS group. The baseline characteristics of the 4 groups were compared to identify differences. The relationship between polysomnography parameters and nocturnal ambulatory blood pressure monitoring results and the factors causing nocturnal blood pressure fluctuations in older adults with OSAS were further analyzed.

Results The nocturnal blood pressure fluctuation (NBPF) index of the normal OSAS group, the mild OSAS group, the moderate OSAS group, and the severe OSAS group were 1.89 ± 1.58, 3.35 ± 5.40, 3.90 ± 6.40, and 16.60 ± 27.70, respectively, indicating that the NBPF index gradually increased with the increasing severity of OSAS (P < 0.05). According to findings from the partial correlation analysis, the NBPF index was positively correlated with apnea-hypopnea index (AHI), micro-awakening index (MAI), percentage of cumulative time with oxygen saturation under 90% in the total sleep time (TS90%), oxygen desaturation index (ODI), and the longest apnea time (LAT) (P < 0.05), and negatively correlated with the lowest oxygen saturation (LSpO₂) and sleep quality index (SQI) (P < 0.05). The mean nocturnal systolic and diastolic blood pressures were positively correlated with AHI, ODI, and TS90% (P < 0.05). A multi-factor regression analysis showed that every time ODI increased by 1 unit, the NBPF index increased by 0.26 units (β = 0.26; 95% CI, 0.03-0.50; P = 0.030), and every time TS90% increased by 1 unit, the NBPF index increased by 26.78 units (β = 26.78; 95% CI, 2.47-51.08; P = 0.031).

Conclusion In older adult OSAS patients without cardiovascular or cerebrovascular disease, fluctuations in blood pressure at night become more pronounced with increasing disease severity. ODI and TS90% are important factors that affect nocturnal blood pressure fluctuations.