Global spatiotemporal trends of cardiovascular diseases due to temperature in different climates and socio-demographic index regions from 1990 to 2019

Butyrate attenuates cold-induced hypertension via gut microbiota and activation of brown adipose tissue

OBJECTIVE

Chronic exposure to cold temperature is known to elevate blood pressure, leading to a condition known as cold-induced hypertension (CIH). Our previous research suggested correlations between alterations in gut microbiota, decrease in butyrate level, and the onset and progression of CIH. However, the role of butyrate in CIH and the underlying mechanisms need further investigation.

METHODS

We exposed Specific Pathogen Free (SPF) rats to continuous cold temperature (4 ± 1 °C) for 6 weeks to establish a CIH rat model. Rats were divided into different groups by dose and duration, and the rats under cold were administered with butyrate (0.5 or 1 g/kg/day) daily. We assessed hypertension-associated phenotypes, pathological morphological changes, and endocrine-related phenotypes of brown adipose tissue (BAT). The effects of butyrate on gut microbiota and intestinal content metabolism were evaluated by 16s RNA sequencing and non-targeted metabolomics, respectively.

RESULTS

The systolic blood pressure (SBP) of rats exposed to cold after supplemented with butyrate were significantly lower than that of the Cold group. Butyrate may increase the species, abundance, and diversity of gut microbiota in rats. Specifically, butyrate intervention enriched beneficial bacterial genera, such as Lactobacillaceae, and decreased the levels of harmful bacteria genera, such as Actinobacteriota and Erysipeiotrichaceae. Cold exposure significantly increased BAT cells and the number of mitochondria. After butyrate supplementation, the levels of peroxisome proliferator-activated receptor gamma coactivator 1a and fibroblast growth factor 21 in BAT were significantly elevated (P < 0.05), and the volume and number of lipid droplets increased. The levels of ANG II and high-density lipoprotein were elevated in the Cold group but decreased after butyrate supplementation.

CONCLUSION

Butyrate may attenuate blood pressure in CIH by promoting the growth of beneficial bacteria and the secretion of beneficial derived factors produced by BAT, thus alleviating the elevation of blood pressure induced by cold. This study demonstrates the anti-hypertensive effects of butyrate and its potential therapeutic mechanisms, offering novel insights to the prevention and treatment of CIH in populations living or working in cold environments.

Burden of non-communicable diseases attributable to high temperature in a changing climate from 1990 to 2019: a global analysis

BACKGROUND

With global climate change, the health threats of ambient high temperature have received widespread attention. However, latest spatio-temporal patterns of the non-communicable diseases (NCDs) burden attributable to high temperature have not been systematically reported. We aimed to analyze vulnerable areas and populations based on a detailed profile for the NCDs burden attributable to high temperature globally.

METHODS

We obtained data from the Global Burden of Diseases (GBD) Study (2019) to describe the temporal and spatial patterns of NCDs burden attributable to high temperature globally from 1990-2019. Then we analyzed the differences by region, sex, and socio-demographic index (SDI). Finally, the age‑period‑cohort (APC) model was utilized to explore the age, period, and cohort effects of NCDs mortality caused by high temperature.

RESULTS

In 2019, the number of deaths and Disability-adjusted life years (DALYs) from high-temperature-related NCDs was about 150,000 and 3.4 million globally, of which about 70% were in South Asia and North Africa and Middle East, and the burden was higher in men. Among 204 countries and territories, the highest age-standardized mortality rate (ASMR) and age-standardized DALY rate (ASDR) were observed in Oman and United Arab Emirates, respectively. The global burden showed an upward trend from 1990 to 2019, with an EAPC of 3.66 (95%CI: 3.14-4.18) for ASMR and 3.68 (95%CI: 3.16-4.21) for ASDR. Cardiovascular diseases were the main contributors to the global burden of high-temperature-related NCDs in 2019. The age and period effect in APC model showed an increasing trend globally. There was a significant negative correlation between SDI and both ASMR (r = -0.17) and ASDR (r = -0.20) from 1990 to 2019.

CONCLUSION

There was an increasing trend of the global burden of high-temperature-related NCDs. The burden was likely to be higher in males and the elderly, as well as in countries and regions with less economically and socially developed and in tropical climates. Surveillance and prevention measures should be implemented with a focus on these vulnerable areas and susceptible populations.

Cold exposure, gut microbiota and health implications: A narrative review

Temperature has been recognized as an important environmental factor affecting the composition and function of gut microbiota (GM). Although research on high-temperature impacts has been well studied, knowledge about the effect of cold exposure on GM remains limited. This narrative review aims to synthesize the latest scientific findings on the impact of cold exposure on mammalian GM, and its potential health implications. Chronic cold exposure could disrupt the α-diversity and the composition of GM in both experimental animals and wild-living hosts. Meanwhile, cold exposure could impact gut microbial metabolites, such as short-chain fatty acids. We also discussed plausible biological pathways and mechanisms by which cold-induced changes may impact host health, including metabolic homeostasis, fitness and thermogenesis, through the microbiota-gut-brain axis. Intriguingly, alterations in GM may provide a tool for favorably modulating the host response to the cold temperature. Finally, current challenges and future perspectives are discussed, emphasizing the need for translational research in humans. GM could be manipulated by utilizing nutritional strategies, such as probiotics and prebiotics, to deal with cold-related health issues and enhance well-being in populations living or working in cold environments.

Age-Period-Cohort Analysis of Cardiovascular Mortality Attributable to Environmental Risks in China

INTRODUCTION

This study aimed to analyze changes in cardiovascular disease (CVD) mortality attributable to major environmental risks in China during 1990-2019, and their associations with age, period, and birth cohort.

METHODS

Mortality data were obtained from the Global Burden of Disease Study 2019. Major environmental risks included ambient particulate matter pollution (APMP), household air pollution from solid fuels (HAP), low temperature, high temperature, and lead exposure. Age-period-cohort modeling was used to estimate the overall annual percentage change in CVD mortality (net drift), annual percentage change for each age group (local drift), expected longitudinal age-specific rate (longitudinal age curve), period and cohort relative risks (RRs, period/cohort effects) between 1990 and 2019. Analyses were conducted in 2021-2022.

RESULTS

In China, five major environmental risks led to 1.62 million CVD deaths in 2019. Among these risks, the primary contributor to CVD mortality transited from HAP in 1990 to APMP in 2019. There was also an improvement in attributable CVD mortality rates for low temperature and lead exposure during 1990-2019, while an unfavorable trend was noted for high temperature. The longitudinal age curve demonstrated increased attributable CVD mortality rates with age groups for all environmental risks, with similar patterns for both sexes. Period and cohort RRs suggested generally improved risks of attributable CVD mortality for HAP, low temperature, and lead exposure, but worsening risks for APMP and high temperature in both genders, except for period risks after 2010-2014 for APMP in both sexes, period risks after 2000-2004 for high temperature in females, and cohort risks in cohorts born after 1955 for APMP and high temperature in females.

CONCLUSIONS

Over the study period, there was a significant improvement in attributable CVD mortality rates in China for HAP, low temperature and lead exposure, but an unfavorable trend was noted for APMP and high temperature.

Impacts of exposure to humidex on cardiovascular mortality: a multi-city study in Southwest China

BACKGROUND

Many studies have reported the association between ambient temperature and mortality from cardiovascular disease (CVD). However, the health effects of humidity are still unclear, much less the combined effects of temperature and humidity. In this study, we used humidex to quantify the effect of temperature and humidity combined on CVD mortality.

METHODS

Daily meteorological, air pollution, and CVD mortality data were collected in four cities in southwest China. We used a distributed lag non-linear model (DLNM) in the first stage to assess the exposure-response association between humidex and city-specific CVD mortality. A multivariate meta-analysis was conducted in the second stage to pool these effects at the overall level. To evaluate the mortality burden of high and low humidex, we determined the attributable fraction (AF). According to the abovementioned processes, stratified analyses were conducted based on various demographic factors.

RESULTS

Humidex and the CVD exposure-response curve showed an inverted "J" shape, the minimum mortality humidex (MMH) was 31.7 (77th percentile), and the cumulative relative risk (CRR) was 2.27 (95% confidence interval [CI], 1.76-2.91). At extremely high and low humidex, CRRs were 1.19 (95% CI, 0.98-1.44) and 2.52 (95% CI, 1.88-3.38), respectively. The burden of CVD mortality attributed to non-optimal humidex was 21.59% (95% empirical CI [eCI], 18.12-24.59%), most of which was due to low humidex, with an AF of 20.16% (95% eCI, 16.72-23.23%).

CONCLUSIONS

Low humidex could significantly increase the risk of CVD mortality, and vulnerability to humidex differed across populations with different demographic characteristics. The elderly (> 64 years old), unmarried people, and those with a limited level of education (1-9 years) were especially susceptible to low humidex. Therefore, humidex is appropriate as a predictor in a CVD early-warning system.