Age and sex distribution of beat-to-beat blood pressure variability after transient ischemic attack and minor stroke: A population-based study

Abstract

Background: Beat-to-beat blood pressure variability is associated with increased stroke risk but its importance at different ages is unclear.

Aims: To determine the age-sex distribution of blood pressure variability in patients with transient ischemic stroke or minor stroke.

Methods: In consecutive patients within six weeks of transient ischemic stroke or non-disabling stroke (Oxford Vascular Study), non-invasive blood pressure was measured beat-to-beat over five minutes (Finometer). The age-sex distribution of blood pressure variability (residual coefficient of variation) was determined for systolic blood pressure and diastolic blood pressure. The risk of top-decile blood pressure variability was estimated (logistic regression), unadjusted, and adjusted for age, sex, and cardiovascular risk factors.

Results: In 908 of 1013 patients, excluding 54 in atrial fibrillation and 51 with low quality recordings, residual coefficient of variation was positively skewed with a median systolic residual coefficient of variation of 4.2% (IQR 3.2-5.5) and diastolic residual coefficient of variation of 3.9% (3.0-5.5), with 90th centile thresholds of 7.2 and 7.3%. Median systolic residual coefficient of variation was higher in patients under 50 years (4.5 and 3.0-5.3) compared to 60-70 years (4.1 and 3.2-5.2), but rose to 4.5% (3.5-6.9) above 80 years, with an increasingly positive skew. The proportion of patients with markedly elevated blood pressure variability in the top-decile increased significantly per decade (OR 1.72, p < 0.001), after adjustment for sex and risk factors.

Conclusions: Median beat-to-beat blood pressure variability fell in midlife, reflecting loss of physiological, organized blood pressure variability. However, rates of markedly elevated blood pressure variability significantly increased with greater age, suggesting that blood pressure variability may be particularly important in older patients.

Keywords: Age; TIA; blood pressure variability; hypertension; minor stroke; sex; transient ischemic stroke.

Figure 1.

Distribution of mean and variability in systolic and diastolic blood pressure across the population. Histograms are presented with density curves. BP variability is presented as coefficient of variation (CV) and as residual coefficient of variation after linear detrending of the data (rCV, %). SBP: systolic blood pressure; DBP: diastolic blood pressure.

Figure 2.

Mean values of mean, maximum and rCV for systolic (SBP) and diastolic (DBP) blood pressure, stratified by sex and quintiles of age. Results are presented as the mean and confidence interval for each group. rCV is calculated as the coefficient of variation of de-trended recordings. Age groups are given in quintiles: <54.2; 54.3–64.7; 64.8–71.4; 71.5–77.7; >77.7 years.