Objective: Abnormalities in circadian blood pressure (BP) variation, particularly increase in nocturnal BP, have been reported to be risk factors for cardiovascular disease, although the factors associated with BP abnormalities are not fully understood. This study aimed to clarify possible associations of sleep characteristics, including sleep fragmentation, sleep disordered breathing, and nocturia, with sleep BP by simultaneous multiday measurements.
Methods: A cross-sectional study evaluated 5959 community participants having home-measured data on nocturnal BP change (sleep BP - awaking BP), sleep characteristics, and sleep disordered breathing. Sleep characteristics including the fragmentation index were assessed using wrist-wearable actigraphy, whereas sleep disordered breathing was assessed by 3% oxygen desaturation index obtained using a finger-type monitor. The number of nocturnal urinations was recorded in a sleep diary.
Results: Mean nocturnal SBP change was -8.5 ± 7.9%. A 3% oxygen desaturation index was associated with the BP change independently of the basic covariates (β = 0.051, P = 0.001), although the association became insignificant (P = 0.196) after adjusting the fragmentation index (β = 0.105, P < 0.001). The association of the fragmentation index was also insignificant (P = 0.153) after adjusting measurement season (middle season: β = 0.163, P < 0.001; summer season: β = 0.249, P < 0.001). In contrast, the frequency of urination showed strong and independent association (β = 0.140, P < 0.001), with smaller nocturnal BP drop in participants with frequent urination.
Conclusion: Subjective sleep estimates and frequent nocturnal urination may represent a potential risk for circadian BP abnormalities.