Background - The Generalised Unsafety Theory of Stress, a novel stress explanation, considers the stress response as a default mode of the body, which is always active independently from stressors...Show moreBackground - The Generalised Unsafety Theory of Stress, a novel stress explanation, considers the stress response as a default mode of the body, which is always active independently from stressors unless it is inhibited based on perceiving safety. GUTS suggests there are compromised domains where stress is chronically released despite a lack of clear stressors, and the organism is unable to inhibit the stress mechanism mostly because of perceiving generalised unsafety around. One of these compromised domains is believed to be urban environments as they cannot provide sufficient signs of safety, and they mainly consist property of strangers. Natural environments in contrast are believed to provide signs of safety and therefore decrease stress levels. Using meta-analysis, this current research aimed to find and summarize evidence from existing studies reporting that urban environments are associated with increased levels of stress, Method - In total, 12 studies, collected from Web of Science database, were included in six meta-analyses conducted on heart rate variability (high frequency, low frequency/high frequency), saliva cortisol, blood pressure (systolic and diastolic), and heart rate data of healthy adult participants during and after exposure to urban and natural environments. Results - Statistically significant increased heart rate was found after a walk in the urban environment (g = 0.37, 95% CI: 0.20; 0.50, p <0.0001). High frequency heart rate variability was significantly lower after an urban walk(unknown baseline balance group: g = -0.33, 95% CI: -0.55; -0.11; baseline balanced: g = -2.52, 95% CI: -3.25; -1.78). Low frequency heart rate variability was significantly higher during the urban walk (unknown baseline balance group: g = 0.33, 95% CI: 0.49; 1.80; baseline balanced: g = 2.52, 95% CI: 1.78; 3.26). Subgroup analyses and funnel plots for heart rate variability showed a possible small-study effect in the baseline balanced groups. Blood pressure and cortisol measurements showed no significant effect and were ambiguous because of high heterogeneity and small number of included studies. Conclusions - Heart rate variability and heart rate measures indicated a higher stress level in urban than in natural environments providing an example of prolonged stress without stressors, explainable by GUTS. For blood pressure and cortisol no such evidence was provided. However, the results should be carefully interpreted because of high between-study heterogeneity and other limitations of these studies. Further research into stress measurements and effects of natural and urban environment on stress are required to provide reliable evidence.Show less
Background: Long-term exposure to road traffic noise is associated with the prevalence of hypertension. To understand more about this exposure-response relationship, it is essential to examine this...Show moreBackground: Long-term exposure to road traffic noise is associated with the prevalence of hypertension. To understand more about this exposure-response relationship, it is essential to examine this association with baseline blood pressure measurements. However, theories of possible mechanisms explaining the chronic physiological effects of road traffic noise exposure are limited. Furthermore, the findings of epidemiological studies investigating this relationship are inconsistent and different factors seem to influence the strength of the relationship. A critical evaluation of these studies seems warranted. Purpose: This study aims to gain more theoretical and empirical insight into the association between road traffic noise and resting blood pressure measurements. Methods: Web of Science, PubMed and reference lists were used. Six articles were included, consisting of information about ten studies. A meta-analysis on the association between road traffic noise and blood pressure among adults was performed. The ten effect size estimates were based on the data of 146,339 subjects in total. Results: A 0.195 mmHg (95% CI: 0.004, 0.386) higher systolic blood pressure per 10 dB increase was found. Road traffic noise was not associated with diastolic blood pressure. However, the sensitivity analysis revealed stronger associations with diastolic blood pressure for high-quality studies and stronger associations with systolic blood pressure for nighttime noise exposure. Conclusion: Long-term exposure to road traffic noise had a significant positive association with systolic blood pressure, perhaps strongest at night, and a nonsignificant positive association with diastolic blood pressure. The significant moderating effect of study quality on diastolic blood pressure is a possible explanation for this inconsistency. Further research is required to get a more comprehensive understanding of the association between road traffic noise and blood pressure.Show less
