Heart rate variability, the dynamic nature of the retinal microvasculature and cardiac stress: providing insight into the brain-retina-heart link: the SABPA study

Acute mental stress-induced alpha or beta-adrenergic reactivity patterns linked to unique cardiometabolic risk profiles

Cardiometabolic risk may differ based on a stress-induced alpha(α)-adrenergic response versus a predominant beta(β)-adrenergic response. Whether these responses might serve as significant markers of distinct cardiometabolic risk profiles based on hemodynamic reactivity remain unknown. We (1) characterized predominant α-and β-adrenergic hemodynamic response patterns to acute mental stress; and (2) determined the cardiometabolic risk profile within predominant α-or β-adrenergic responders, irrespective of age, sex, or ethnicity. We included 117 South African teachers (aged 20-65 years) and administered an acute mental stress task (Color-Word-Conflict test) for one-minute. Participants' hemodynamic response profiles were characterized as predominant α-adrenergic (decreases in cardiac output (CO) and Windkessel arterial compliance (Cwk) (lowest quartile)) (n = 48) and β-adrenergic (increases in CO, Cwk (highest quartile)) responses (n = 69) via Finometer beat-to-beat hemodynamic monitoring. Ambulatory-BP was measured and the number of 24 H-ischemic events determined by ECG. Cardiometabolic markers were analyzed using fasting blood samples, and abnormal glucose tolerance (Abnl-GT), combining prediabetes and diabetes, was defined as glycated hemoglobin (HbA1c) ≥ 5.7% and/or fasting glucose > 100 mg/dL and/or diabetes medication usage. Predominant α-adrenergic responders presented with an overall poorer cardiometabolic profile, with higher levels of HbA1c, insulin, greater insulin resistance and higher total cholesterol and lower HDL-cholesterol. Adjusted analyses indicated that a predominant α-adrenergic profile had higher odds of central obesity (P = 0.031), low HDL-cholesterol (P = 0.042), 24-H-hypertension (P < 0.001), cardiac stress (P = 0.025), ischemic events (P = 0.048) and medium-to-high 10-year stroke probability (P < 0.001), compared to β-adrenergic responders. In the β-adrenergic responders, higher odds for ischemic events, stroke probability and Abnl-GT were found (all P ≤ 0.022), compared to α-adrenergic responders. Independent of age, sex or ethnicity, the risk profile identified in predominant α-adrenergic responders mainly involved the effects of a high-pressure system, cardiac stress, and ischemia. Whereas in predominant β-adrenergic responders, the risk profile pointed to a more metabolic and hyperperfusion injury-related cardiometabolic risk.

Allostatic load and cardiometabolic health in a young adult South African population: the African-PREDICT study

Sustained stress, assessed as a high allostatic load score (ALS), is an independent cardiovascular disease (CVD) risk factor in older adults but its associations in young people are undefined. Since neurological maturation impacts stress adaptation and CVD risk, we assessed the relationship of ALS with CVD profile by using a tiered approach stratified by age [emerging adults (EA) aged 20-24 yr vs. young adults (YA) aged 25-30 yr] and ALS (high vs. low). In 1,054 healthy participants of the African Prospective Study on Early Detection and Identification of Cardiovascular Disease and Hypertension (African-PREDICT), we determined: 1) ALS in EA versus YA; 2) the relationship between ALS and cardiovascular (CV) health, and 3) the odds of high ALS > 4 to identify masked hypertension (HT) and prediabetes as cardiometabolic outcomes. A nine-component, four-domain ALS was compiled: neuroendocrine [dehydroepiandrosterone (DHEA), cortisol], inflammatory [interleukin-6 (IL-6), C-reactive protein (CRP)], cardiovascular [systolic blood pressure (SBP) and diastolic blood pressure (DBP)], and metabolic [total cholesterol, high density lipoprotein cholesterol (HDL-cholesterol), body mass index (BMI)]. Retinal vessel caliber, pulse wave velocity (PWV), and cardiac structure and function were assessed. Median ALS was 3 (range: 1-9). A high-ALS > 4 was more common in YA versus EA (47 vs. 35%, P = 0.032). Higher ALS associated with narrower retinal arteries (P < 0.01), greater PWV (P ≤ 0.01), lower diastolic function (P < 0.01), and left ventricular (LV) function (P < 0.01). High-ALS increased the odds of having masked hypertension, prediabetes, narrower retinal arteries, higher LV mass, poorer diastolic and ventricular functions (all P ≤ 0.01), in EA and YA independent of traditional CVD risk factors. The composite ALS identified early-stress dysregulation in cardiometabolic health and higher odds for masked hypertension and prediabetes in young adults. Cumulative stress may be a modifiable, independent cardiometabolic risk factor in younger populations that needs further investigation.NEW & NOTEWORTHY This is the first study to assess the effect of stress, as a composite allostatic load score, on micro-, macrovascular, and central cardiac features in healthy emerging and young adults, independent of traditional cardiovascular risk markers. It exemplifies independent stress-induced changes throughout the cardiovascular tree, which may increase the risk of cardiometabolic complications, masked hypertension, and prediabetes. Sustained stress may be a key etiological factor in cardiometabolic disease development in a young population.

Daytime napping is associated with retinal microcirculation: a large population-based study in China

STUDY OBJECTIVES

To investigate the association between daytime napping and retinal microcirculation.

METHODS

This is a cross-sectional study from a prospective population-based cohort. 2,662 participants were recruited after quota sampling. Information on napping was collected through face-to-face interviews. Retinal vascular calibers (RVCs), including central retinal arteriolar equivalent (CRAE), central retinal venular equivalent (CRVE), and arterio-to-venous ratio (AVR), were obtained from fundus photography. Multivariate regression and restricted cubic spline curve were performed to determine the association between RVCs and daytime napping duration.

RESULTS

56.4% participants reported daytime napping regularly. Compared to no nap, daytime nap was related to higher CRAE, with nap duration of 0.5-1 h showing the most significant association. 0.5-1 h daytime nappers displayed an average of 4.18 µm (95% confidence interval [CI] 2.45-5.91, p < 0.001) wider CRAE than non-nappers after adjustment. No significant association was found between CRVE and daytime napping. Moreover, individuals with 0.5-1 h daytime napping had a lower risk for AVR reduction (odds ratio [OR] 0.70, 95% confidence interval [CI] 0.56-0.86, p = 0.001) than non-nappers. Similar association persisted in non-hypertensive population. Restricted cubic spline indicated a J-shaped relationship between AVR reduction and nap duration.

CONCLUSION

Retinal microcirculation was positively associated with self-reported 0.5-1 h daytime napping. Better indicators of retinal microcirculation were probably related to nap duration in a J-shaped manner. Also, the possibly beneficial role of 0.5-1 h daytime napping on retinal microcirculation might be independent of clinically diagnosed vascular diseases.

Delayed retinal vein recovery responses indicate both non-adaptation to stress as well as increased risk for stroke: the SABPA study

OBJECTIVES

Low or high sympatho-adrenal-medullary axis (SAM) and hypothalamic-pituitary-adrenal axis (HPA) dysregulation reflect chronic stress. Retinal vessel dynamics may relate to SAM, HPA activity and stroke risk. Our objectives were therefore to assess the relationships between retinal vessel, SAM and HPA responses, and to determine stroke risk.

METHODS

A prospective bi-ethnic gender cohort (n = 275, 45 ± 9 years) was included. Urine/serum/saliva samples for SAM [norepinephrine:creatinine ratio (u-NE)] and HPA [adrenocorticotrophic hormone (ACTH), cortisol] were obtained at baseline, three-year follow up and upon flicker light-induced provocation. Diastolic ocular perfusion pressure was measured as a marker of hypo-perfusion. Retinal arterial narrowing and venous widening calibres were quantified from digital images in the mydriatic eye. A validated stress and stroke risk score was applied.

RESULTS

An interaction term was fitted for venous dilation in u-NE tertiles (p ≤ 0.05) and not in u-NE median/quartiles/quintiles. Independent of race or gender, tertile 1 (low u-NE) had a 112% increase in u-NE, decreases in cortisol, and no changes in ACTH over three years (positive feedback). Tertile 3 (high u-NE) contradictorily had decreases in u-NE and cortisol, and increases in ACTH (negative feedback). In tertile 1, reduced arterial dilation, and faster arterial vasoconstriction and narrowing were related to higher SAM activity and hypo-perfusion (p ≤ 0.05), whereas delayed venous dilation, recovery and widening were related to cortisol hypo-secretion (p ≤ 0.05). In tertile 1, delayed venous recovery responses predicted stress and stroke risk [odds ratio 4.8 (1.2-19.6); p = 0.03]. These associations were not found in u-NE tertiles 2 and 3.

CONCLUSIONS

In response to low norepinephrine, a reflex increase in SAM activity occurred, enhancing arterial vasoconstriction and hypo-perfusion. Concomitant HPA dysregulation attenuated retinal vein vasoactivity and tone, reflecting delayed vein recovery responses and non-adaptation to stress. These constrained vein recovery responses are indicative of increased chronic stress and stroke risk.