85 - Preterm Birth and its Association with Altered Renal Sodium Handling in Response to Mental Stress in Young Adults

Poster Number: 85
Publication Number: 85.324

Nicholas W. Tully, Wake Forest School of Medicine of Wake Forest Baptist Medical Center, Winston-Salem, NC, United States; Andrew M. South, Wake Forest School of Medicine of Wake Forest Baptist Medical Center, Winston Salem, NC, United States

Background: Early-life programming due to prematurity and very low birth weight (VLBW; < 1500 g) contribute to later hypertension, with this effect amplified in individuals born female, but the underlying mechanisms are not fully known. Experimental data suggest that altered pressure natriuresis (an increase in renal perfusion pressure to promote sodium excretion) may be an important contributing mechanism. Adults with primary hypertension exhibit blunted pressure natriuresis in response to sympathetic arousal, but this has not been described in adults born preterm.

Objective: We hypothesized that young adults born preterm with VLBW will have a blunted pressure natriuresis response to mental stress compared to those born term.

Design/Methods: In this long-term prospective cohort of 161 individuals aged 18–23 years, 129 (80%) born preterm with VLBW and 32 (20%) controls born term, we measured urine sodium/creatinine (UNaCr) before and after a 30-min mental stress test and non-invasive continuous blood pressure every 2 min prior to and during the stress test. We defined our outcome, pressure natriuresis, using three estimates on the continuous scale: (i) relative change in UNaCr per relative change in MAP; (ii) percent change in UNaCr per percent change in MAP; and (iii) sodium excretion rate per change in MAP. We further defined blunted response as ≤0 for each of these estimates. We used unadjusted generalized linear models to estimate the association between prematurity and the outcome and tested for effect modification by sex.

Results: Study participants’ mean age was 19.8 years (SD 0.9) of whom 56% were female. On unadjusted analyses, the preterm-term difference in the relative change in UNaCr per change in MAP was β=0.11/mmHg (95% CI -0.06 to 0.27). When defined as the percent change, the difference in pressure natriuresis between the two groups was β=42.4% (4.7 to 80.2). Lastly, the difference in sodium excretion rate relative to change in MAP was β=0.08 min/mmHg (-0.03 to 0.18). Across the three measures of pressure natriuresis, the relative risk of blunted response was 1.2 (0.68 to 2.1). We observed no evidence of effect modification by sex.Conclusion(s): Except for percent change in UNaCr relative to percent change in MAP, we did not observe a difference in pressure natriuresis in response to mental stress between those born preterm with VLBW and those born term. Ongoing analyses include investigating other measures of pressure natriuresis and adjusted multivariable models.
Nicholas Tully CV.pdf