Effects of different cold-air exposure intensities on the risk of cardiovascular disease in healthy and hypertensive rats

Short-term effects of cold spells on plasma viscosity: Results from the KORA cohort study in Augsburg, Germany

As the underlying mechanisms of the adverse effects of cold spells on cardiac events are not well understood, we explored the effects of cold spells on plasma viscosity, a blood parameter linked to cardiovascular disease. This cross-sectional study involved 3622 participants from the KORA S1 Study (1984-1985), performed in Augsburg, Germany. Exposure data was obtained from the Bavarian State Office for the Environment. Cold spells were defined as two or more consecutive days with daily mean temperatures below the 3^rd, 5^th, or 10^th percentile of the distribution. The effects of cold spells on plasma viscosity were explored by generalized additive models with distributed lag nonlinear models (DLNM). We estimated cumulative effects at lags 0-1, 0-6, 0-13, 0-20, and 0-27 days separately. Cold spells (mean temperature <3^rd, <5^th or <10^th percentile) were significantly associated with an increase in plasma viscosity with a lag of 0-1 days [%change of geometric mean (95% confidence interval): 1.35 (0.06-2.68), 1.35 (0.06-2.68), and 2.49 (0.34-4.69), respectively], and a lag of 0-27 days [18.81 (8.97-29.54), 17.85 (8.29-28.25), and 7.41 (3.35-11.0), respectively]. For the analysis with mean temperature <3^rd or 10^th percentile, we also observed significant associations at lag 0-20 days [8.34 (0.43-16.88), and 4.96 (1.68, 8.35), respectively]. We found that cold spells had significant immediate and longer lagged effects on plasma viscosity. This finding supports the complex interplay of multiple mechanisms of cold on adverse cardiac events and enriches the knowledge about how cold exposure acts on the human body.

Effects of cold and hot temperature on metabolic indicators in adults from a prospective cohort study

BACKGROUND

Previous studies have found that exposed to low and high outdoor temperature was associated with cardiovascular diseases morbidity and mortality. The risk factors for cardiovascular disease include high blood lipid, high uric acid (UA) and high fasting plasma glucose (FPG). However, few studies have explored the effects of low and high temperature on these metabolic indicators.

OBJECTIVE

To explore the effect of low and high temperature on metabolic indicators in adults from northwest of China.

METHODS

Based on a prospective cohort study, a total of 30,759 individuals who participated in both baseline and first follow-up from 2011 to 2015 were selected in this study. The meteorological observation data and environmental monitoring data were collected in the same period. Associations between cold and hot temperature and blood lipid (total cholesterol (TC), triglycerides (TG), low density lipoprotein-cholesterol (LDL-C), and high density lipoprotein-cholesterol (HDL-C)), UA and FPG were conducted with mixed effect models after adjusting for confounding factors.

RESULTS

A nonlinear relationship between outdoor temperature and metabolic indicators was found. For the cold effects, each 5 °C decrease of mean temperature was associated with an increase of 5.07% (95% CI: 3.52%, 6.63%) in TG and 2.85% (95% CI: 2.18%, 3.53%) in UA, While a decrease of 3.38% (95% CI: 2.67%, 4.09%) in HDL-C and 1.26% (95% CI: 0.48%, 2.04%) in LDL-C. For the heat effects, each 5 °C increase in mean temperature was associated with 1.82% (95% CI: 0.89%, 2.76%), 0.56% (95% CI: 0.11%, 1.00%), 5.82% (95% CI: 4.58%, 7.06%), 9.02% (95% CI: 7.17%, 10.87%), 0.20% (95% CI: 0.01%, 0.40%), and 1.22% (95% CI: 0.19%, 2.24%) decrease in TC, TG, HDL-C, LDL-C, UA and FPG. Age, smoking, drinking, high-oil diet and hyperlipidemia might modify the association between mean temperature and metabolic indicators.

CONCLUSION

There was a significant effect of cold and hot temperature on metabolic indicators in a high altitude area of northwestern China. These results provide a basis for understanding the underlying mechanism of the influence of temperature on metabolic diseases.

The nonlinear association between outdoor temperature and cholesterol levels, with modifying effect of individual characteristics and behaviors

Few studies have been conducted to investigate the underlying mechanisms of the effect of temperature on cardiovascular disease at population level, especially among Chinese population. A total of 56,039 participants were recruited from Kailuan cohort study, China. The lipoprotein profile indicators, including triglycerides (TG), low-density lipoprotein (LDL), and high-density lipoprotein, were collected. Non-linear associations between temperature and the lipoprotein profile indicators were examined using a nonlinear function for temperature. Stratified analyses were performed in groups by individual characteristics (age, gender, and body mass index) and individual behaviors (physical activities and smoking habits). Generally, a non-linear relationship was found between cholesterol levels and temperature. A 1 °C decrease in temperature below the threshold was related with 0.004 mmol/L (95% CI 0.0004, 0.008), 0.022 mmol/L (95% CI 0.020, 0.025), and 0.009 mmol/L (95% CI 0.008, 0.011) increase in TG, LDL, and HDL, respectively; a 1 °C increase in temperature above the threshold was associated with 0.005 mmol/L (95% CI 0.003, 0.007), 0.012 mmol/L (95% CI 0.009, 0.015), and 0.002 mmol/L (95% CI 0.001, 0.004) increase in TG, LDL, and HDL, respectively. Stratified analyses showed that effect estimates on TG and LDL were larger among females, subjects with higher BMI, and those with smoking habits, while effect estimates on HDL were smaller among these subjects (expect for female). Our results suggest both cold and hot effect of temperature on cholesterol. Furthermore, females, and people with higher BMI or smoking habit may be more susceptible to outdoor temperature.

What is cold-related mortality? A multi-disciplinary perspective to inform climate change impact assessments

BACKGROUND

There is a growing discussion regarding the mortality burdens of hot and cold weather and how the balance between these may alter as a result of climate change. Net effects of climate change are often presented, and in some settings these may suggest that reductions in cold-related mortality will outweigh increases in heat-related mortality. However, key to these discussions is that the magnitude of temperature-related mortality is wholly sensitive to the placement of the temperature threshold above or below which effects are modelled. For cold exposure especially, where threshold effects are often ill-defined, choices in threshold placement have varied widely between published studies, even within the same location. Despite this, there is little discussion around appropriate threshold selection and whether reported associations reflect true causal relationships - i.e. whether all deaths occurring below a given temperature threshold can be regarded as cold-related and are therefore likely to decrease as climate warms.

OBJECTIVES

Our objectives are to initiate a discussion around the importance of threshold placement and examine evidence for causality across the full range of temperatures used to quantify cold-related mortality. We examine whether understanding causal mechanisms can inform threshold selection, the interpretation of current and future cold-related health burdens and their use in policy formation.

METHODS

Using Greater London data as an example, we first illustrate the sensitivity of cold related mortality to threshold selection. Using the Bradford Hill criteria as a framework, we then integrate knowledge and evidence from multiple disciplines and areas- including animal and human physiology, epidemiology, biomarker studies and population level studies. This allows for discussion of several possible direct and indirect causal mechanisms operating across the range of 'cold' temperatures and lag periods used in health impact studies, and whether this in turn can inform appropriate threshold placement.

RESULTS

Evidence from a range of disciplines appears to support a causal relationship for cold across a range of temperatures and lag periods, although there is more consistent evidence for a causal effect at more extreme temperatures. It is plausible that 'direct' mechanisms for cold mortality are likely to occur at lower temperatures and 'indirect' mechanisms (e.g. via increased spread of infection) may occur at milder temperatures.

CONCLUSIONS

Separating the effects of 'extreme' and 'moderate' cold (e.g. temperatures between approximately 8-9 °C and 18 °C in the UK) could help the interpretation of studies quoting attributable mortality burdens. However there remains the general dilemma of whether it is better to use a lower cold threshold below which we are more certain of a causal relationship, but at the risk of under-estimating deaths attributable to cold.

Health assessment of future PM2.5 exposures from indoor, outdoor, and secondhand tobacco smoke concentrations under alternative policy pathways in Ulaanbaatar, Mongolia

INTRODUCTION

Winter air pollution in Ulaanbaatar, Mongolia is among the worst in the world. The health impacts of policy decisions affecting air pollution exposures in Ulaanbaatar were modeled and evaluated under business as usual and two more-strict alternative emissions pathways through 2024. Previous studies have relied on either outdoor or indoor concentrations to assesses the health risks of air pollution, but the burden is really a function of total exposure. This study combined projections of indoor and outdoor concentrations of PM2.5 with population time-activity estimates to develop trajectories of total age-specific PM2.5 exposure for the Ulaanbaatar population. Indoor PM2.5 contributions from secondhand tobacco smoke (SHS) were estimated in order to fill out total exposures, and changes in population and background disease were modeled. The health impacts were derived using integrated exposure-response curves from the Global Burden of Disease Study.

RESULTS

Annual average population-weighted PM2.5 exposures at baseline (2014) were estimated at 59 μg/m3. These were dominated by exposures occurring indoors, influenced considerably by infiltrated outdoor pollution. Under current control policies, exposures increased slightly to 60 μg/m3 by 2024; under moderate emissions reductions and under a switch to clean technologies, exposures were reduced from baseline levels by 45% and 80%, respectively. The moderate improvement pathway decreased per capita annual disability-adjusted life year (DALY) and death burdens by approximately 40%. A switch to clean fuels decreased per capita annual DALY and death burdens by about 85% by 2024 with the relative SHS contribution increasing substantially.

CONCLUSION

This study demonstrates a way to combine estimated changes in total exposure, background disease and population levels, and exposure-response functions to project the health impacts of alternative policy pathways. The resulting burden analysis highlights the need for aggressive action, including the elimination of residential coal burning and the reduction of current smoking rates.

Cardiovascular response to thermoregulatory challenges

A growing number of extreme climate events are occurring in the setting of ongoing climate change, with an increase in both the intensity and frequency. It has been shown that ambient temperature challenges have a direct and highly varied impact on cardiovascular health. With a rapidly growing amount of literature on this issue, we aim to review the recent publications regarding the impact of cold and heat on human populations with regard to cardiovascular disease (CVD) mortality/morbidity while also examining lag effects, vulnerable subgroups, and relevant mechanisms. Although the relative risk of morbidity/mortality associated with extreme temperature varied greatly across different studies, both cold and hot temperatures were associated with a positive mean excess of cardiovascular deaths or hospital admissions. Cause-specific study of CVD morbidity/mortality indicated that the sensitivity to temperature was disease-specific, with different patterns for acute and chronic ischemic heart disease. Vulnerability to temperature-related mortality was associated with some characteristics of the populations, including sex, age, location, socioeconomic condition, and comorbidities such as cardiac diseases, kidney diseases, diabetes, and hypertension. Temperature-induced damage is thought to be related to enhanced sympathetic reactivity followed by activation of the sympathetic nervous system, renin-angiotensin system, as well as dehydration and a systemic inflammatory response. Future research should focus on multidisciplinary adaptation strategies that incorporate epidemiology, climatology, indoor/building environments, energy usage, labor legislative perfection, and human thermal comfort models. Studies on the underlying mechanism by which temperature challenge induces pathophysiological response and CVD await profound and lasting investigation.

Effects of Simulated Heat Waves with Strong Sudden Cooling Weather on ApoE Knockout Mice

This study analyzes the mechanism of influence of heat waves with strong sudden cooling on cardiovascular diseases (CVD) in ApoE−/− mice. The process of heat waves with strong sudden cooling was simulated with a TEM1880 meteorological-environment simulation chamber according to the data obtained at 5 a.m. of 19 June 2006 to 11 p.m. of 22 June 2006. Forty-eight ApoE−/− mice were divided into six blocks based on their weight. Two mice from each block were randomly assigned to control, heat wave, temperature drop, and rewarming temperature groups. The experimental groups were transferred into the climate simulator chamber for exposure to the simulated heat wave process with strong sudden temperature drop. After 55, 59, and 75 h of exposure, the experimental groups were successively removed from the chamber to monitor physiological indicators. Blood samples were collected by decollation, and the hearts were harvested in all groups. The levels of heat stress factors (HSP60, SOD, TNF, sICAM-1, HIF-1α), cold stress factors (NE, EPI), vasoconstrictor factors (ANGII, ET-1, NO), and four items of blood lipid (TC, TG, HDL-C, and LDL-C) were measured in each ApoE−/− mouse. Results showed that the heat waves increased the levels of heat stress factors except SOD decreased, and decreased the levels of vasoconstrictor factors and blood lipid factors except TC increased. The strong sudden temperature drop in the heat wave process increased the levels of cold stress factors, vasoconstrictor factors and four blood lipid items (except the level of HDL-C which decreased) and decreased the levels of heat stress factors (except the level of SOD which increased). The analysis showed that heat waves could enhance atherosclerosis of ApoE−/− mice. The strong sudden temperature drop during the heat wave process increased the plasma concentrations of NE and ANGII, which indicates SNS activation, and resulted in increased blood pressure. NE and ANGII are vasoconstrictors involved in systemic vasoconstriction especially in the superficial areas of the body and conducive to increased blood pressure. The increase in the blood lipid levels of TG, LDL-C, TC, and LDL-C/HDL-C further aggravated CVD. This paper explored the influence mechanism of the heat waves with sudden cooling on CVD in ApoE−/− mice.

Effects of moderate strength cold air exposure on blood pressure and biochemical indicators among cardiovascular and cerebrovascular patients

The effects of cold air on cardiovascular and cerebrovascular diseases were investigated in an experimental study examining blood pressure and biochemical indicators. Zhangye, a city in Gansu Province, China, was selected as the experimental site. Health screening and blood tests were conducted, and finally, 30 cardiovascular disease patients and 40 healthy subjects were recruited. The experiment was performed during a cold event during 27–28 April 2013. Blood pressure, catecholamine, angiotensin II (ANG-II), cardiac troponin I (cTnI), muscle myoglobin (Mb) and endothefin-1 (ET-1) levels of the subjects were evaluated 1 day before, during the 2nd day of the cold exposure and 1 day after the cold air exposure. Our results suggest that cold air exposure increases blood pressure in cardiovascular disease patients and healthy subjects via the sympathetic nervous system (SNS) that is activated first and which augments ANG-II levels accelerating the release of the norepinephrine and stimulates the renin-angiotensin system (RAS). The combined effect of these factors leads to a rise in blood pressure. In addition, cold air exposure can cause significant metabolism and secretion of Mb, cTnI and ET-1 in subjects; taking the patient group as an example, ET-1 was 202.7 ng/L during the cold air exposure, increased 58 ng/L compared with before the cold air exposure, Mb and cTnI levels remained relatively high (2,219.5 ng/L and 613.2 ng/L, increased 642.1 ng/L and 306.5 ng/L compared with before the cold air exposure, respectively) 1-day after the cold exposure. This showed that cold air can cause damage to patients’ heart cells, and the damage cannot be rapidly repaired. Some of the responses related to the biochemical markers indicated that cold exposure increased cardiovascular strain and possible myocardial injury.