Impact of seasonality and air pollutants on carotid-femoral pulse wave velocity and wave reflection in hypertensive patients

Abstract

ObjectiveThe effects of seasonality on blood pressure (BP) and cardiovascular (CV) events are well established, while the influence of seasonality and other environmental factors on arterial stiffness and wave reflection has never been analyzed. This study evaluated whether seasonality (daily number of hours of light) and acute variations in outdoor temperature and air pollutants may affect carotid-femoral pulse wave velocity (PWV) and pressure augmentation.Design and method731 hypertensive patients (30–88 years, 417 treated) were enrolled in a cross-sectional study during a 5-year period. PWV, central BP, Augmentation Index (AIx) and Augmentation Pressure (AP) were measured in a temperature-controlled (22–24°C) room. Data of the local office of the National Climatic Data Observatory were used to estimate meteorological conditions and air pollutants (PM10, O3, CO, N2O) exposure on the same day.ResultsPWV (mean value 8.5±1.8 m/s) was related to age (r = 0.467, p<0.001), body mass index (r = 0.132, p<0.001), central systolic (r = 0.414, p<0.001) and diastolic BP (r = 0.093, p = 0.013), daylight hours (r = -0.176, p<0.001), mean outdoor temperature (r = -0.082, p = 0.027), O3 (r = -0.135, p<0.001), CO (r = 0.096, p = 0.012), N2O (r = 0.087, p = 0.022). In multiple linear regression analysis, adjusted for confounders, PWV remained independently associated only with daylight hours (β = -0.170; 95% CI: -0.273 to -0.067, p = 0.001). No significant correlation was found between pressure augmentation and daylight hours, mean temperature or air pollutants. The relationship was stronger in untreated patients and women. Furthermore, a positive, independent association between O3 levels and PWV emerged in untreated patients (β: 0.018; p = 0.029; CI: 0.002 to 0.034) and in women (β: 0.027; p = 0.004; CI: 0.009 to 0.045).ConclusionsPWV showed a marked seasonality in hypertensive patients. Environmental O3 levels may acutely reduce arterial stiffness in hypertensive women and in untreated patients.

The effects of experimental, meteorological, and physiological factors on short-term repeated pulse wave velocity measurements, and measurement difficulties: A randomized crossover study with two devices

“…The omission of a significant interaction term between temperature and MAP in these models may explain inconsistencies, as exclusion of the term from cfPWV model in our study also resulted in a non-significant main effect of temperature, while a simple correlation also showed that cfPWV is inversely associated with temperature. While the mechanism underlying this relationship is beyond the scope of our study, it has been proposed that cold-induced sympathetic activation may account for the dependence of cfPWV readings on outdoor temperature in conditions where the room temperature is constant ( 25 , 68 ). Having said that, it appears that at lower outdoor temperatures, resting time in supine position in the temperature-controlled room might be extended beyond 10 min to allow for temperature accommodation, or alternatively, repeated measurements might be taken in a season with higher outdoor temperatures, such as those around 25 ° C. More research with different adaptation times is needed to determine whether temperature accommodation is indeed responsible for the observed effect.…”

“…While the negative relationship between outdoor temperature and BP readings has been observed in many studies ( 63 – 67 ), similar relationship was hypothesized for arterial stiffness, but studies reported inconsistent results. Di Pilla et al reported that in an unadjusted regression analysis, cfPWV recorded by SphygmoCor was weakly and inversely associated with outdoor temperature, but not in a multiple regression analysis that controlled for age, BMI, SBP, DBP, daylight hours, O 3 , CO, and N 2 O ( 25 ). In repeated measures ANOVA analysis, Kita et al demonstrated considerable sessional change of an arterial stiffness index—arterial velocity pulse index, with higher stiffness observed during a summer ( 26 ).…”

Sex and Gender Aspects in Vascular Ageing – Focus on Epidemiology, Pathophysiology, and Outcomes

“…Differences between men and women in the impact of exposure to pollutants on vascular ageing biomarkers emerged as well: both air and noise pollution have a greater impact on CV health in women than in men [84,85], mirroring what is well established for cigarette smoking [86]. Underlying mechanisms are largely unknown, but both sex-and gender-related factors are likely involved.…”

Environmental Factors and Hypertension

“…Few studies have assessed how chronic exposure to outdoor air pollution influences arterial stiffness [33], which is a key marker of early vascular aging and related biunivocally to hypertension [34]. Furthermore, in hypertensive women a significant and positive association between aortic stiffness and outdoor O 3 concentrations was found, suggesting that this subgroup might be more vulnerable to the effects of acute exposure to air pollution [35]. However, other substances may have a detrimental effect on vascular function and structure as well.…”