Smaller Arteriolar Diameters Research Articles

Recent versus chronic fine particulate air pollution exposure as determinant of the retinal microvasculature in school children

BackgroundMicrovascular changes may represent an underlying mechanism through which exposure to fine particulate matter with a diameter ≤ 2.5µm (PM2.5) contributes to age-related disease development. We investigated the effect of recent and chronic exposure to PM2.5 on the microcirculation, exemplified by retinal vessel diameters, using repeated measurements in 8- to 12-year-old children. Methods221 children (49.1% girls; mean age 9.9 years) were examined repeatedly (25 one, 124 two, and 72 three times) adding up to 489 retinal vessel examinations. Same-day exposure to PM2.5 was measured at school. In addition, recent (same and previous day) and chronic (yearly mean) exposure was modelled at the child's residence using a high-resolution interpolation model. Residential proximity to major roads was also assessed. Changes in retinal vessel diameters associated with recent and chronic exposures were estimated using mixed models, while adjusting for other known covariates such as sex, age, BMI, blood pressure and birth weight. ResultsEach 10µg/m³ increment in same-day exposure to PM2.5 measured at school was associated with 0.35µm (95% CI: 0.09–0.61µm) narrower retinal arterioles and 0.35µm (−0.03 to 0.73µm) wider venules. Children living 100m closer to a major road had 0.30µm (0.05–0.54µm) narrower arterioles. ConclusionsBlood vessel diameters of the retinal microcirculation of healthy school-aged children respond to same-day PM2.5 exposure. Furthermore, children living closer to major roads had smaller arteriolar diameters. Our results suggest that the microcirculation, with retinal microvasculature as a proxy in this study, is a pathophysiological target for air pollution in children.

Retinal vessel calibers predict long-term microvascular complications in type 1 diabetes: the Danish Cohort of Pediatric Diabetes 1987 (DCPD1987).

Diabetic neuropathy, nephropathy, and retinopathy cause significant morbidity in patients with type 1 diabetes, even though improvements in treatment modalities delay the appearance and reduce the severity of these complications. To prevent or further delay the onset, it is necessary to better understand common underlying pathogenesis and to discover preclinical biomarkers of these complications. Retinal vessel calibers have been associated with the presence of microvascular complications, but their long-term predictive value has only been sparsely investigated. We examined retinal vessel calibers as 16-year predictors of diabetic nephropathy, neuropathy, and proliferative retinopathy in a young population-based Danish cohort with type 1 diabetes. We used semiautomated computer software to analyze vessel diameters on baseline retinal photos. Calibers of all vessels coursing through a zone 0.5-1 disc diameter from the disc margin were measured and summarized as the central artery and vein equivalents. In multiple regression analyses, we found wider venular diameters and smaller arteriolar diameters were both predictive of the 16-year development of nephropathy, neuropathy, and proliferative retinopathy. Early retinal vessel caliber changes are seemingly early markers of microvascular processes, precede the development of microvascular complications, and are a potential noninvasive predictive test on future risk of diabetic retinopathy, neuropathy, and nephropathy.

Retinal vessel diameters and risk of stroke

Retinal vessels may provide information on cerebral vascular pathology, because they share many features with cerebral vessels. A smaller ratio of the retinal arteriolar-to-venular diameters reportedly predicts the risk of stroke. It is unclear if this is due to arteriolar narrowing or venular dilation. To investigate whether smaller arteriolar or larger venular diameters are related to the risk of stroke and cerebral infarction. This study was based on the prospective population-based Rotterdam Study and included 5,540 participants of 55 years or over, who had gradable fundus transparencies and were free of stroke at baseline (1990 to 1993). For each participant, retinal arteriolar and venular diameters were measured on digitized images of one eye. Follow-up for first-ever stroke was complete until January 1, 2002. After a mean follow-up of 8.5 years, 411 participants had a stroke, of whom 259 had cerebral infarction. Larger venular diameters were associated with an increased risk of stroke (hazard ratio [HR] adjusted for age and sex per SD increase: 1.12 [95% CI: 1.02 to 1.24]) and cerebral infarction (HR: 1.15 [95% CI: 1.02 to 1.29]). Smaller arteriolar diameters were neither related to the risk of stroke (HR per SD decrease: 1.02 [95% CI: 0.93 to 1.13]) nor to the risk of cerebral infarction (HR: 1.02 [95% CI: 0.90 to 1.15]). After additional adjustment for other cardiovascular risk factors, the results did not change. Larger retinal venular diameters are associated with an increased risk of stroke and cerebral infarction. The role of venules in cerebrovascular disease warrants further exploration.

Are Inflammatory Factors Related to Retinal Vessel Caliber?

To examine the relationship of systemic markers of inflammation, endothelial dysfunction, and serum folate level to retinal vessel diameter. Cross-sectional analyses were completed for data from a random sample of 396 persons aged 50 to 86 years who underwent a baseline examination from 1988 to 1990. Standardized protocols for blood collection and measurement of markers were used. Diameters of arterioles and venules were measured from digitized photographs. Standard univariate and multivariate analyses were performed. While controlling for age, smoking status, diabetes status, serum high-density lipoprotein cholesterol, and hematocrit, wider retinal venular diameters were associated with higher serum high-sensitivity C-reactive protein, interleukin 6, and amyloid A levels. While controlling for age, systolic and diastolic blood pressure, smoking, serum high-density lipoprotein cholesterol level, and gout, smaller arteriolar diameters were associated with higher serum amyloid A and lower serum albumin and folate levels but not high-sensitivity C-reactive protein or interleukin 6 levels. Levels of serum soluble intercellular adhesion molecule-1 and serum soluble E-selectin, markers of endothelial dysfunction, were not associated with retinal arteriolar or venular diameters. These data show an association of inflammatory markers with larger retinal venular diameter, suggesting that retinal venular caliber may be a marker of systemic inflammation.

Retinal Vessel Diameters and the Risk of Incident Age-Related Macular Disease: The Rotterdam study

To study the relationship between retinal vessel diameters and incident age-related macular disease (iAMD). Prospective population-based cohort study. Persons (55 years and older) from the Rotterdam Study, who participated at the baseline (1990-1993) and 1 of 2 follow-up examinations (1993-1994 and 1997-1999). In the current analysis, 4345 participants who were free of AMD at baseline and had gradable macular transparencies at both baseline and follow-up examination were included. Also, arteriolar and venular diameters were measured on digitized baseline images. Stereoscopic transparencies of the macular region were graded according to the International Classification and Grading System for AMD. Incidence of AMD was defined as the development of soft distinct drusen with pigmentary changes or indistinct or reticular drusen with or without pigmentary changes (early iAMD) or atrophic or neovascular AMD (late iAMD). Logistic regression models were used to assess these associations, adjusting for age, gender, and follow-up time and, additionally, for smoking, body mass index, intima-media thickness, systolic blood pressure, and total and high-density lipoprotein cholesterol levels. Incidence of AMD. After a mean follow-up time of 5.2 years, a total of 374 persons developed early and late iAMD. Neither arteriolar nor venular diameters were related to the risk of iAMD. The odds ratio (OR) per standard deviation (SD) decrease in arteriolar diameter was 1.03 (95% confidence interval [CI], 0.93-1.15), and the OR per SD increase in venular diameter was 1.04 (95% CI, 0.93-1.16). After categorizing the retinal vessel diameters into quintiles, there was no trend. After stratifying on age, only persons 75 years and older with smaller arteriolar diameters were at a borderline significant increased risk of iAMD: OR/SD decrease in arteriolar diameters adjusted for age, gender, follow-up time, and other cardiovascular risk factors, 1.24 (95% CI, 0.94-1.63). Overall retinal vessel diameters were not related to the risk of iAMD in this general elderly population.

Prospective cohort study of retinal vessel diameters and risk of hypertension

Objective To examine the relation between diameters of the retinal arterioles and 10 year incidence of hypertension.Design Population based prospective cohort study.Setting Beaver Dam eye study.Participants 2451 normotensive people aged...

Are retinal arteriolar or venular diameters associated with markers for cardiovascular disorders? The Rotterdam Study.

A lower retinal arteriolar-to-venular ratio (AVR) has been suggested to reflect generalized arteriolar narrowing and to predict the risk of cardiovascular diseases. The contribution of the separate arteriolar and venular diameters to this AVR is unknown. Thus, associations between retinal arteriolar and venular diameters, and the AVR on the one hand and blood pressure, atherosclerosis, inflammation markers, and cholesterol levels on the other were examined in the Rotterdam Study. In this cross-sectional population-based study, for one eye of each subject (> or =55 years; n = 5674), retinal arteriolar and venular diameters (in micrometers) of the blood columns were summed on digitized images. At baseline blood pressures, cholesterol levels, and markers of atherosclerosis and inflammation were also measured. With increasing blood and pulse pressures, retinal arteriolar and venular diameters and the AVR decreased significantly and linearly. Lower arteriolar diameters were associated with increased carotid intima-media thickness. Larger venular diameters were associated with higher carotid plaque score, more aortic calcifications, lower ankle-arm index, higher leukocyte count, higher erythrocyte sedimentation rate, higher total serum cholesterol, lower HDL, higher waist-to-hip ratio, and smoking. A lower AVR was related to increased carotid intima-media thickness, higher carotid plaque score, higher leukocyte count, lower HDL, higher body mass index, higher waist-to-hip ratio, and smoking. Because larger venular diameters are associated with atherosclerosis, inflammation, and cholesterol levels, the AVR does not depend only on generalized arteriolar narrowing due to the association between smaller arteriolar diameters and higher blood pressures. These data indicate that retinal venular diameters are variable and may play their own independent role in predicting cardiovascular disorders.

Active and passive arteriolar regulation in spontaneously hypertensive rats.

This study determined to what extent active and passive wall tensions increase in in vivo intestinal arterioles of 13- to 15-week-old and 25- to 27-week-old spontaneously hypertensive rats (SHR) to maintain normal or smaller arteriolar diameters during microvascular hypertension. Acetylcholine and nitroprusside were used to determine whether vascular muscle relaxation to endothelium-derived relaxing factor or cyclic GMP is impaired. Large arterioles of hypertensive rats have passive tension-circumference relations that are steeper and shifted to the left compared with those of age-matched controls; passive resistance to distension limits vasodilation in hypertensive rats except at their naturally elevated arteriolar pressure. Passive tension contributes approximately 30% of the total resting tension in arterioles of hypertensive and normotensive rats because a greater passive tension occurs at the 20% to 25% constricted resting diameter in hypertensive rats. Absolute and relative changes in the diameter of SHR arterioles during acetylcholine and nitroprusside application were equal to or greater than those in Wistar-Kyoto rats. However, reduction in active tension was suppressed in older SHR and remained approximately 50% higher than that found in older Wistar-Kyoto rats during drug application. Vasoconstriction and increased passive resistance to distension of the arteriolar wall diminish the active tension required to maintain normal or smaller resting diameters against microvascular hypertension. However, the elevated microvascular pressure in hypertensive rats is required to allow near-normal dilation to compensate for their increased passive resistance to stretch and decreased ability to relax active tension through cyclic GMP mechanisms.