The morning blood pressure surge: a dynamic and challenging concept

The relationship between vitamin D and short-term blood pressure variability

OBJECTIVES

This study aimed to evaluate the relationships between serum levels of 25-hydroxyvitamin D (25(OH)D) and short-term blood pressure variability (BPV) in newly diagnosed hypertensive patients.

METHODS

One hundred newly diagnosed patients with stage one essential hypertension were included and divided into two groups, the deficient and non-deficient groups, according to their 25(OH)D level. The blood pressure was recorded automatically by a portable ambulatory blood pressure monitor for 24 h.

RESULTS

In the present study, there was no significant relationship between vitamin D levels and short-term BPV or other parameters derived from ambulatory blood pressure monitoring (ABPM) (P > 0.05). Age (r = 0.260, P = 0.009), serum phosphorus (r = 0.271, P = 0.007), and cholesterol levels (r = 0.310, P = 0.011) were positively correlated with 25(OH)D levels, while glomerular filtration rate (r = -0.232, P = 0.021) negatively correlated with vitamin D levels. There was no crude or adjusted relationship between the levels of 25(OH)D and any parameters of ABPM in multiple linear regression analysis.

CONCLUSION

Although the relationship between vitamin D levels and cardiovascular diseases has been confirmed, vitamin D deficiency does not cause an increase in cardiovascular risk by influencing the short-term BPV or other parameters derived from ABPM.

Impact of various night-time period definitions on nocturnal ambulatory blood pressure

BACKGROUND

Several definitions of night-time BP exist for the calculation of nocturnal blood pressure (BP) based on 24-h BP measurements. How much these methods differ regarding the resulting nocturnal blood pressure values, under which circumstances these differences become clinically meaningful, and under which circumstances diary-adjusted measurements should be used preferentially remains uncertain.

METHODS

Data of 512 24-h BP recordings were analysed regarding differences in nocturnal BP based on three alternative definitions of night-time: 2300-0700 h, 0100-0500 h, and diary-adjusted measures.

RESULTS

Mean systolic nocturnal BP between 2300-0700 h was 2.5 mmHg higher than between 0100 and 0500 h and 1.6 mmHg higher than diary adjusted estimates. Up to 38.3% of individuals showed BP differences of more than 5 mmHg when comparing temporal definitions of night-time, resulting in significant proportions of individuals being re-classified as hypertensive. When diary-derived sleeping patterns differed by less than 2 h from the 2300 to 0700 h fixed time definition, mean BP discrepancies remained below 3 mmHg. Absolute time discrepancies between diary and 2300-0700 h fixed time definition of 2-4, 4-8 or at least 8 h led to SBP/DBP differences of 4.1/3.1, 6.8/6.1, and 14.5/9.1mmHg, respectively.

CONCLUSION

Average differences of nocturnal BP between varying definitions in study/cohort data are small and would be of limited relevance in many settings. However, substantial differences can be observed in individual cases, which may affect clinical decision-making in specific patients. In patients whose sleeping patterns differs by more than 2 h from defined fixed night-times, diaries should be used for adjustment.