Abstract P177: Self-Reported Blood Pressure is Comparable to Measured Blood Pressure in a Study of General Population Participants

Abstract

Background: Blood pressure (BP) is an established risk factor for several chronic diseases. Clinical measurement of BP is the preferable method to assess BP, but may not be feasible in large-scale epidemiologic studies. Self-reported BP has been widely collected as an alternative. It has not been well-studied whether self-reported BP is comparable to measured BP, particularly in the general population. Method: We conducted a cross-sectional analysis in a large, mail-based randomized controlled trial - VITamin D and OmegA-3 TriaL (VITAL) - to compare BP levels assessed using different methods. Participants of VITAL were women aged ≥55 years and men aged ≥50 years, free of cardiovascular disease and cancer. Among a total of 21,025 VITAL participants who reported BP in multiple categories on the baseline questionnaire, 1,955 also had seated BP measured at baseline clinic-based or home-based visits, and 269 also completed assessment of 24 hour ambulatory BP (24-hr ABP) monitoring. We included 264 VITAL participants who had all three BP measures in analysis, converted the self-reported BP levels to ordinal variable by using the median of each category, and examined the associations between the different BP measurements with estimation of correlation and linear regression. Results: The 264 VITAL participants were on average aged 63.8 years, 59% women, 23.5% African-Americans, 54.9% with post-college education, and 6.4% with a history of hypertension. The mean (SD) of self-reported BP, seated BP, and 24-hr ABP were 120.1 (9.1), 120.2 (12.5), and 128.2 (11.3) mmHg for systolic BP (SBP) and 73.0 (6.3), 72.3 (9.8), and 76.9 (7.9) mmHg for diastolic BP (DBP), respectively. Spearman correlation coefficients (Spearman r) between BP measured using three different methods ranged from 0.37 (self-reported vs. seated) to 0.49 (seated vs. 24-hr ambulatory) for SBP and from 0.30 (seated vs. 24-hr ambulatory) to 0.34 (self-reported vs. seated) for DBP (all P<0.0001). The age-adjusted regression coefficients (β coefficients) and 95% confidence intervals (CI) of self-reported BP in relation to measured BP were 0.55 (95% CI: 0.39-0.71) and 0.33 (95% CI: 0.15-0.51) for seated SBP and DBP, and 0.47 (95% CI: 0.33-0.61) and 0.46 (95% CI: 0.32-0.60) for 24-hr ambulatory SBP and DBP, respectively. The β coefficients of seated BP in relation to 24-hr ABP were also statistically significant, of 0.42 (95% CI: 0.33-0.52) and 0.19 (95% CI: 0.10-0.29) for 24-hr ambulatory SBP and DBP, respectively. The β coefficients were generally similar across subgroups of participants by age, gender, and ethnicity, and were consistently stronger among those with higher education. Conclusion: In this large, mail-based study of older men and women from general US population, self-reported BP correlates reasonably well with both seated BP and 24-hr ABP. Self-reported BP can be used to estimate measured BP in large-scale epidemiologic studies.