Graded Association Between Kidney Function and Impaired Orthostatic Blood Pressure Stabilization in Older Adults

Abstract

BackgroundImpaired orthostatic blood pressure (BP) stabilization is highly prevalent in older adults and is a predictor of end‐organ injury, falls, and mortality. We sought to characterize the relationship between postural BP responses and the kidney.Methods and ResultsWe performed a cross‐sectional analysis of 4204 participants from The Irish Longitudinal Study on Ageing, a national cohort of community‐dwelling adults aged ≥50 years. Beat‐to‐beat systolic and diastolic BP were measured during a 2‐minute active stand test. The primary predictor was cystatin C estimated glomerular filtration rate (eGFR) categorized as follows (mL/min per 1.73 m2): ≥90 (reference, n=1414); 75 to 89 (n=1379); 60 to 74 (n=942); 45 to 59 (n=337); <45 (n=132). We examined the association between eGFR categories and (1) sustained orthostatic hypotension, defined as a BP drop exceeding consensus thresholds (systolic BP drop ≥20 mm Hg±diastolic BP drop ≥10 mm Hg) at each 10‐second interval from 60 to 110 seconds inclusive; (2) pattern of BP stabilization, characterized as the difference from baseline in mean systolic BP/diastolic BP at 10‐second intervals. The mean age of subjects was 61.6 years; 47% of subjects were male, and the median eGFR was 82 mL/min per 1.73 m2. After multivariable adjustment, participants with eGFR <60 mL/min per 1.73 m2 were approximately twice as likely to have sustained orthostatic hypotension (P=0.008 for trend across eGFR categories). We observed a graded association between eGFR categories and impaired orthostatic BP stabilization, particularly within the first minute of standing.ConclusionsWe report a novel, graded relationship between diminished eGFR and impaired orthostatic BP stabilization. Mapping the postural BP response merits further study in kidney disease as a potential means of identifying those at risk of hypotension‐related events.

Impaired orthostatic blood pressure stabilization and reduced hemoglobin in chronic kidney disease

“…The effect size of this association was significant: every 10 mL/min/1.73 m 2 decrease in eGFR was associated with an ≈1/0.4 mm Hg increase in the orthostatic SBP/DBP reduction. This association is in line with findings from previous large‐scale community‐based studies . Using a widely adopted diagnostic criteria, we identified that 16.0% of the subjects had orthostatic hypotension.…”

Impairments in Hemodynamic Responses to Orthostasis Associated with Frailty: Results from The Irish Longitudinal Study on Ageing (TILDA)

“…Linear mixed-effects models (Stata 'mixed' command) with a participant-level random intercept were used to model the recovery in BP or heart rate from 10 to 110 seconds after standing, comparable with modelling change over time in a longitudinal analysis. 21,22 The primary outcome measure was percentage of BP or heart rate recovered over time standing. Residual variance across time was modelled using an autoregressive correlation matrix with a lag of 1 to account for stronger correlations between time points that are close together.…”

“…Consequently, we parameterized time using linear splines with knots at 20 and 30 seconds and the slopes between these knots representing the different phases of the stand (10-20, 20-30, 30-110 seconds). 21 These re-parameterized time variables were included in the models as fixed effects.…”

“…Linear mixed‐effects models (Stata ‘mixed’ command) with a participant‐level random intercept were used to model the recovery in BP or heart rate from 10 to 110 seconds after standing, comparable with modelling change over time in a longitudinal analysis . The primary outcome measure was percentage of BP or heart rate recovered over time standing.…”

“…Conceptually, the recovery of BP and heart rate can be broken down into an initial rapid recovery phase followed by stabilization and a more steady state phase of remaining stable or gradual further recovery. Consequently, we parameterized time using linear splines with knots at 20 and 30 seconds and the slopes between these knots representing the different phases of the stand (10–20, 20–30, 30–110 seconds) . These re‐parameterized time variables were included in the models as fixed effects.…”