Cross-sectional analysis of racial differences in hydration and neighborhood deprivation in young adults

Apparently healthy young black adults report lower total fluid intake and exhibit higher plasma copeptin than young White adults

Underhydration is associated with higher plasma copeptin concentration ([copeptin]), an arginine vasopressin surrogate associated with multiple chronic diseases. Middle-aged and older Black individuals are more likely to be underhydrated and exhibit higher [copeptin] than White individuals. However, limited data exists on racial differences in [copeptin] in young adults. Therefore, we tested the hypothesis that apparently healthy young Black adults would report lower fluid intake and exhibit higher plasma [copeptin] than young White adults. Participants (n = 86; sex: 40F/46M; race: White n = 48, Black n = 38; age: 21±2 years, BMI: 25±4 kg/m2) completed 3-day food and fluid diaries. We operationalized beverages into 8 categories (water, sugar-sweetened beverages, milk/non-dairy alternatives, juice, nonaloric beverages (eg, diet drinks), coffee or tea (noncaloric), coffee or tea (caloric), and alcohol) and measured plasma [copeptin]. We assessed racial differences in fluid intake and [copeptin] and also examined relations between race, fluid intake, and [copeptin] via regression and correlation analyses. Compared with White adults, Black adults consumed less total fluid (64.0[31.3] vs. 89.7[53.6] oz), water, alcohol, and coffee/tea (noncaloric and caloric) but more juice (ps < .05). Black participants exhibited higher plasma [copeptin] (6.38[4.83] vs. 4.45[2.92] pmol/L, P = .021). In the whole cohort, plasma [copeptin] was negatively correlated with water intake (ρ= -0.249, P = .021). However, racial differences in [copeptin] were attenuated by 27% when accounting for total fluid intake. Black young adults reported lower fluid intake and exhibited higher plasma [copeptin] than White young adults. Interventions are needed to address racial disparities in hydration practices, potentially attenuating racial differences in [copeptin] and related health disparities.

Do not sleep on vitamin D: vitamin D is associated with sleep variability in apparently healthy adults

Vitamin D is associated with sleep quality and duration, but it is unclear whether vitamin D status influences sleep variability. Therefore, we sought to determine whether vitamin D status was associated with sleep variability in healthy adults. We assessed objective sleep, including timing and duration standard deviation (SD) using the Philips Actiwatch Spectrum and subjective sleep quality using the Pittsburgh Sleep Quality Index (PSQI) in 130 adults. We measured plasma 25(OH)D concentration to assess vitamin D. We used one-way ANOVAs and Kruskal-Wallis tests to compare sleep in participants characterized as vitamin D deficient (<20 ng/mL), insufficient (21-29 ng/mL), and sufficient (>30ng/mL). We used covariate-adjusted linear regression to assess associations between vitamin D status and sleep metrics. We compared differences in "low" and "high" sleep variability based on vitamin D status using the Chi-squared test. There was an effect of vitamin D status on sleep timing SD (Kruskal-Wallis, P = 0.021) and sleep duration SD (Kruskal-Wallis, P < 0.001). There was an inverse association between vitamin D status with sleep duration SD (after covariate adjustment R2 = 0.267, P < 0.001, deficient vs. sufficient P = 0.050, insufficient vs. sufficient P = 0.022). There was no effect of vitamin D status on objective sleep duration, efficiency, or PSQI scores (P > 0.05). We did not observe differences in "low" and "high" sleep timing SD based on vitamin D status (χ2 = 5.43, P = 0.066), but we did for sleep duration SD (χ2 = 22.4, P < 0.001). Our data indicate that individuals with poor vitamin D status exhibit greater objective sleep variability. Clinical Trial Registry: https://www.clinicaltrials.gov/; Unique identifiers NCT04334135, NCT04244604, and NCT04576338.NEW & NOTEWORTHY Our findings reveal that individuals with lower circulating vitamin D concentrations experience greater sleep variability compared with those with higher circulating concentrations. This supports the growing body of evidence suggesting an important link between vitamin D status and sleep health.

Relationship between fluid intake, hydration status and cortisol dynamics in healthy, young adult males

Background

Previous studies have identified links between fluid intake, hydration related hormones and cortisol measured at one timepoint but have not considered how hydration may influence cortisol dynamics throughout the day. This study assessed associations between hydration status (copeptin, urinary osmolality, urine volume) and habitual fluid intake with cortisol dynamics.

Methods

The day before (DB) a 6-h laboratory visit, 29 male participants (age, 23±4y; BMI, 25.5 ± 4.3 kg/m2; body fat, 17.3 ± 9.3 %) provided 24-h urine samples and a fasted blood sample for hydration status assessment, recorded their 24-h fluid intake for three days prior, and provided 10 saliva samples to assess cortisol dynamics from DB into the evening of the laboratory visit. Calculated indices of cortisol dynamics included: nocturnal cortisol rise (NCR - salivary cortisol rise from bed to awakening), peak salivary cortisol (peak SCORT - highest cortisol of all samples), cortisol awakening response (ΔCAR - difference between high morning sample and awakening sample), area under the curve with respect to ground (AUCG) and increase (AUCI), and diurnal cortisol slope (DCS - rate of change in cortisol from awakening to bed). The relationships between fluid intake or hydration status and cortisol dynamics were analyzed by separating participants into fluid intake tertile groups and by regressing cortisol dynamics on the continuous variables of total fluid intake (TFI) or hydration biomarkers.

Results

There were no between-group differences for ΔCAR (p = 0.89), AUCG (p = 0.57), AUCI (p = 0.48), peak SCORT (p = 0.14), NCR (p = 0.95), DCS (p = 0.22), or serum cortisol (p = 0.61). TFI was not associated with log (peak SCORT) (p = 0.49), ΔCAR (p = 0.61), AUCG (p = 0.76), or AUCI (p = 0.56). Copeptin was not associated with log (peak SCORT) (p = 0.99), ΔCAR (p = 0.22), AUCG (p = 0.69) or AUCI (p = 0.18). Urinary hydration markers were not associated with any measures of cortisol dynamics (p > 0.05). These null effects were consistent when controlling for physical activity, sleep, and body fat percentage.

Conclusion

In the absence of dehydrating stimuli, measures of fluid intake or hydration status may not be associated with cortisol dynamics in young healthy males.

Associations between urine specific gravity and race/ethnicity at the population level: Implications for hydration status categorization

OBJECTIVE

We aimed to evaluate how urine specific gravity (USG) and rates of supposed hypohydration vary by race/ethnicity, and to examine how adjustment for several important factors impacts estimated USG.

METHODS

Using the National Health and Nutrition Examination Survey, this cross-sectional study evaluated a total of 4195 (2098 female, 2097 male) Americans and categorized them as supposedly hypohydrated (USG≥1.020) or not using spot urine samples. USG and prevalence of supposed hypohydration were compared across racial/ethnic groups, separately by gender. The analyses considered the impact of urine creatinine, body composition, age, dietary nutrients, and physical activity.

RESULTS

Differences in supposed hypohydration prevalence were observed by race/ethnicity in men (p = .030) and women (p < .001). In unadjusted models, Black women's USG (1.0189) was higher (p < .05) than all the other race/ethnicity groups' USG (1.0142-1.0171). In men, Blacks' USG (1.0197) was higher (p < .05) than the USG of Whites (1.0177) and other/multi-racial (1.0176) but not Mexican Americans (1.0196) or other Hispanics (1.0192). Adjustments for age, arm circumference, nutrients (protein, sodium, potassium, and moisture), and physical activity minimally influenced USG estimates. Further adjustment for urine creatinine lowered USG for Black women and men by 0.003 and 0.0023, respectively, with no notable lowering of USG in the other races/ethnicities. Supplemental analyses matching Whites and Blacks on age, moisture intake, and poverty-to-income ratio confirmed racial differences in urine creatinine and USG, though the effects were most pronounced in women.

CONCLUSIONS

Using a USG≥1.020 to identify hypohydration in all races/ethnicities may be inappropriate due to, among other factors, differences in urinary creatinine.

Interplay of race and neighborhood deprivation on resting and ambulatory blood pressure in young adults

Nighttime blood pressure (BP) and BP dipping (daytime-nighttime BP) are prognostic for cardiovascular disease. When compared with other racial/ethnic groups, Black Americans exhibit elevated nighttime BP and attenuated BP dipping. Neighborhood deprivation may contribute to disparities in cardiovascular health, but its effects on resting and ambulatory BP patterns in young adults are unclear. Therefore, we examined associations between neighborhood deprivation with resting and nighttime BP and BP dipping in young Black and White adults. We recruited 19 Black and 28 White participants (23 males/24 females, 21 ± 1 yr, body mass index: 26 ± 4 kg/m2) for 24-h ambulatory BP monitoring. We assessed resting BP, nighttime BP, and BP dipping (absolute dip and nighttime:daytime BP ratio). We used the area deprivation index (ADI) to assess average neighborhood deprivation during early and mid-childhood and adolescence. When compared with White participants, Black participants exhibited higher resting systolic and diastolic BP (Ps ≤ 0.029), nighttime systolic BP (114 ± 9 vs. 108 ± 9 mmHg, P = 0.049), diastolic BP (63 ± 8 vs. 57 ± 7 mmHg, P = 0.010), and attenuated absolute systolic BP dipping (12 ± 5 vs. 9 ± 7 mmHg, P = 0.050). Black participants experienced greater average ADI scores compared with White participants [110 (10) vs. 97 (22), P = 0.002], and select ADI scores correlated with resting BP and some ambulatory BP measures. Within each race, select ADI scores correlated with some BP measures for Black participants, but there were no ADI and BP correlations for White participants. In conclusion, our findings suggest that neighborhood deprivation may contribute to higher resting BP and impaired ambulatory BP patterns in young adults warranting further investigation in larger cohorts.NEW & NOTEWORTHY We demonstrate that young Black adults exhibit higher resting blood pressure, nighttime blood pressure, and attenuated systolic blood pressure dipping compared with young White adults. Black adults were exposed to greater neighborhood deprivation, which demonstrated some associations with resting and ambulatory blood pressure. Our findings add to a growing body of literature indicating that neighborhood deprivation may contribute to increased blood pressure.

Differences in urine creatinine and osmolality between black and white Americans after accounting for age, moisture intake, urine volume, and socioeconomic status

Urine osmolality is used throughout research to determine hydration levels. Prior studies have found black individuals to have elevated urine creatinine and osmolality, but it remains unclear which factors explain these findings. This cross-sectional, observational study sought to understand the relationship of self-reported race to urine creatinine and urine osmolality after accounting for age, socioeconomic status, and fluid intake. Data from 1,386 participants of the 2009-2012 National Health and Nutrition Examination Survey were utilized. Age, poverty-to-income ratio (PIR), urine flow rate (UFR), fluid intake, estimated lean body mass (LBM), urine creatinine, and urine osmolality were measured. In a sex-specific manner, black and white participants were matched on age, dietary moisture, UFR, and PIR. Urine creatinine was greater in black men (171 mg/dL) than white men (150 mg/dL) and greater in black women (147 mg/dL) than white women (108 mg/dL) (p < .001). Similarly, urine osmolality was greater in black women than white women (723 vs. 656 mOsm/kg, p = .001), but no difference was observed between white and black men (737 vs. 731 mOsm/kg, p = .417). Estimated LBM was greater in black men (61.8 kg) and women (45.5 kg) than in white men (58.9 kg) and women (42.2 kg) (p≤.001). The strongest correlate of urine osmolality in all race-sex groups was urine creatinine (Spearman ρ = .68-.75). These results affirm that individuals identifying as black produce higher urine creatinine concentrations and, in women, higher urine osmolality after matching for age, fluid intake, and socioeconomic status. The findings suggest caution when comparing urine hydration markers between racial groups.

Acute high-dose MitoQ does not increase urinary kidney injury markers in healthy adults: a randomized crossover trial

Several human studies have used the mitochondrial antioxidant MitoQ. Recent in vitro data indicating that MitoQ may induce nephrotoxicity caused concern regarding the safety of MitoQ on the kidneys, but the doses were supraphysiological. Therefore, we sought to determine whether acute MitoQ elicits changes in urinary biomarkers associated with tubular injury in healthy adults with our hypothesis being there would be no changes. Using a randomized crossover design, 32 healthy adults (16 females and 16 males, 29 ± 11 yr old) consumed MitoQ (100-160 mg based on body mass) or placebo capsules. We obtained serum samples and a 4- to 6-h postcapsule consumption urine sample. We assessed creatinine clearance and urine kidney injury biomarkers including the chitinase 3-like-1 gene product YKL-40, kidney-injury marker-1, monocyte chemoattractant protein-1, epidermal growth factor, neutrophil gelatinase-associated lipocalin, interleukin-18, and uromodulin using multiplex assays. We used t tests, Wilcoxon tests, and Hotelling's T2 to assess global differences in urinary kidney injury markers between conditions. Acute MitoQ supplementation did not influence urine flow rate (P = 0.086, rrb = 0.39), creatinine clearance (P = 0.085, rrb = 0.42), or urinary kidney injury markers (T22,8 = 30.6, P = 0.121, univariate ps > 0.064). Using exploratory univariate analysis, MitoQ did not alter individual injury markers compared with placebo (e.g., placebo vs. MitoQ: YKL-40, 507 ± 241 vs. 442 ± 236 pg/min, P = 0.241; kidney injury molecule-1, 84.1 ± 43.2 vs. 76.2 ± 51.2 pg/min, P = 0.890; and neutrophil gelatinase-associated lipocalin, 10.8 ± 10.1 vs. 9.83 ± 8.06 ng/min, P = 0.609). In conclusion, although longer-term surveillance and data are needed in clinical populations, our findings suggest that acute high-dose MitoQ had no effect on urinary kidney injury markers in healthy adults.NEW & NOTEWORTHY We found acute high-dose mitochondria-targeted antioxidant (MitoQ) supplementation was not nephrotoxic and had no effect on markers of acute kidney injury in healthy adults. These findings can help bolster further confidence in the safety of MitoQ, particularly for future investigations seeking to examine the role of mitochondrial oxidative stress, via acute MitoQ supplementation, on various physiological outcomes.

Salty Subjects: Unpacking Racial Differences in Salt-Sensitive Hypertension

PURPOSE OF REVIEW

To review underlying mechanisms and environmental factors that may influence racial disparities in the development of salt-sensitive blood pressure.

RECENT FINDINGS

Our group and others have observed racial differences in diet and hydration, which may influence salt sensitivity. Dietary salt elicits negative alterations to the gut microbiota and immune system, which may increase hypertension risk, but little is known regarding potential racial differences in these physiological responses. Antioxidant supplementation and exercise offset vascular dysfunction following dietary salt, including in Black adults. Furthermore, recent work proposes the role of racial differences in exposure to social determinants of health, and differences in health behaviors that may influence risk of salt sensitivity. Physiological and environmental factors contribute to the mechanisms that manifest in racial differences in salt-sensitive blood pressure. Using this information, additional work is needed to develop strategies that can attenuate racial disparities in salt-sensitive blood pressure.

Interplay of Race and Neighborhood Deprivation on Ambulatory Blood Pressure in Young Adults

Background

Ambulatory blood pressure (BP) monitoring measures nighttime BP and BP dipping, which are superior to in-clinic BP for predicting cardiovascular disease (CVD), the leading cause of death in America. Compared with other racial/ethnic groups, Black Americans exhibit elevated nighttime BP and attenuated BP dipping, including in young adulthood. Social determinants of health contribute to disparities in CVD risk, but the contribution of neighborhood deprivation on nighttime BP is unclear. Therefore, we examined associations between neighborhood deprivation with nighttime BP and BP dipping in young Black and White adults.

Methods

We recruited 21 Black and 26 White participants (20 M/27 F, mean age: 21 years, body mass index: 25±4 kg/m2) for 24-hour ambulatory BP monitoring. We assessed nighttime BP and BP dipping (nighttime:daytime BP ratio). The area deprivation index (ADI) was used to measure neighborhood deprivation. Associations between ADI and ambulatory BP were examined.

Results

Black participants exhibited higher nighttime diastolic BP compared with White participants (63±8 mmHg vs 58±7 mmHg, p=0.003), and attenuated BP dipping ratios for both systolic (0.92±0.06 vs 0.86±0.05, p=0.001) and diastolic BP (0.86±0.09 vs 0.78±0.08, p=0.007). Black participants experienced greater neighborhood deprivation compared with White participants (ADI scores: 110±8 vs 97±21, p<0.001), and ADI was associated with attenuated systolic BP dipping (ρ=0.342, p=0.019).

Conclusions

Our findings suggest neighborhood deprivation may contribute to higher nighttime BP and attenuated BP dipping, which are prognostic of CVD, and more prevalent in Black adults. Targeted interventions to mitigate the effects of neighborhood deprivation may help to improve nighttime BP.

Clinical Trial Registry

URL: https://www.clinicaltrials.gov; Unique identifier: NCT04576338.