Relation between nocturnal arterial oxygen desaturation and morning blood pressure

Arterial oxygen saturation (SpO2) in volunteers had been previously investigated, and the possibility that a decrease in SpO2 leads to an increase in blood pressure (BP) in airline passengers experiencing oxygen desaturation at high altitudes was reported. It was also shown that mean nocturnal SpO2 was lower in subjects with high-normal BP or mild hypertension than in those with normal BP. The present study investigated nocturnal SpO2, evening BP, and morning BP of volunteers during daily life and examined the relation between nocturnal SpO2 and change in BP (morning BP minus evening BP) to determine the influence of SpO2 on BP.

Sixty-two volunteers (31 men and 31 women) aged 40-87 years (mean: 55.9 +/- 12 [SD] years) underwent measurement of SpO2 and heart rate with a ring-shaped pulse oximeter during sleep at home. Evening BP and morning BP were measured by automatic BP recorder. Subjects that were classified as having high SpO2 (mean nocturnal SpO2 >or= 95%; n = 23, 10 men and 13 women; mean age: 53.2 +/- 12 years) or low SpO2 (mean nocturnal SpO2 < 94%; n = 21, 12 men and 9 women; mean age: 58.7 +/- 13 years) were compared. The relation between mean nocturnal SpO2 and morning BP and the relation between mean nocturnal SpO2 and change in BP were investigated.

There was a significant negative correlation between mean nocturnal SpO2 and morning systolic BP (SBP; r = -0.50, p < 0.01) and between mean nocturnal SpO2 and morning diastolic BP (DBP; r = -0.37, p < 0.01). A significant negative correlation between mean nocturnal SpO2 and change in SBP was observed (r = -0.57, p < 0.01). Morning BP was significantly higher in the low nocturnal SpO2 group than in the high nocturnal SpO2 group (p < 0.001).

The increase in morning BP from evening BP was significantly greater in subjects with a low nocturnal SpO2. The decrease in SpO2 during sleep may affect morning BP rise.