Discrepancies in Observed and Predicted Longitudinal Change in Central Hemodynamic Measures: The Framingham Heart Study

Abstract

Community-based studies have evaluated cross-sectional age relations of aortic stiffness measures, which are not often recapitulated in longitudinal studies. We examined baseline and longitudinal change in aortic stiffness in 5491 participants (mean age, 49.5±14.5 years; 54% women) who attended 2 sequential examinations (6.0±0.6 years apart) of the Framingham Heart Study. Cross-sectional relations of central hemodynamics (mean arterial pressure, central pulse pressure, carotid-femoral pulse wave velocity, and characteristic impedance) with age and risk factors were assessed at visits 1 and 2 (models 1 and 2). We used model 1 coefficients (M 1 ), visit 1 risk factor levels (R 1 ), and age at each visit (A 1 , A 2 ) to estimate values at visits 1 (M 1 R 1 A 1 ) and 2 (M 1 R 1 A 2 ). While using model 1 coefficients, we accounted for age and risk factor level (R 2 ) changes to predict values at visit 2 (M 1 R 2 A 2 ). Using model 2 coefficients (M 2 ) and visit 2 age and risk factor levels, we predicted visit 2 values (M 2 R 2 A 2 ). We calculated predicted change 3 ways: delta1=M 1 R 1 A 2 −M 1 R 1 A 1 , delta2=M 1 R 2 A 2 −M 1 R 1 A 1 , and delta3=M 2 R 2 A 2 −M 1 R 1 A 1 . Delta1 values were biased and correlated poorly with actual changes ( r =−0.02–0.14). For mean arterial pressure, delta1=1.9±0.8 mm Hg ( r =0.14), observed change=−3.3±10.3 mm Hg, and discrepancy=5.2±10.2 mm Hg ( P <0.0001). For characteristic impedance, delta1=7.2±14.7 dyne×sec/cm 5 ( r =0.07), observed change=20.5±68.2 dyne×sec/cm 5 , and discrepancy=−13.3±68.7 dyne×sec/cm 5 ( P <0.0001). Delta2 values were moderately correlated with change ( r =0.17–0.54) but remained biased whereas delta3 values were moderately correlated with change with no bias. Projected change in hemodynamic measures extrapolated from cross-sectional age relations may differ substantially from actual change, particularly for variables with nonlinear age relations.

Longitudinal Hemodynamic Correlates of and Sex Differences in the Evolution of Blood Pressure Across the Adult Lifespan: The Framingham Heart Study

“…In addition, recent reports have shown that projected values for change in blood pressure and various related hemodynamic measures based on cross‐sectional associations can differ from longitudinal assessments of change. 5 , 6 Discrepancies arise in part from marked nonlinearity of age relations of stiffness measures, which necessitates multiple sequential assessments in order to accurately characterize change. Finally, several studies have shown that systolic and pulse pressure increase more rapidly with age in women after midlife, 5 , 7 , 8 , 9 , 10 , 11 possibly because of sex differences in modulation of aortic diameter with advancing age.…”