The acute effects of outdoor temperature on blood pressure in a panel of elderly hypertensive patients

Potential mechanisms of ischemic stroke induced by heat exposure

Recent decades of epidemiological and clinical research have suggested that heat exposure could be a potential risk factor for ischemic stroke. Despite climate factors having a minor impact on individuals compared with established risk factors such as smoking, their widespread and persistent effects significantly affect public health. The mechanisms by which heat exposure triggers ischemic stroke are currently unclear. However, several potential mechanisms, such as the impact of temperature variability on stroke risk factors, inflammation, oxidative stress, and coagulation system changes, have been proposed. This article details the potential mechanisms by which heat exposure may induce ischemic stroke, aiming to guide the prevention and treatment of high-risk groups in hot climates and support public health policy development.

The effects of ambient temperature on non-accidental mortality in the elderly hypertensive subjects, a cohort-based study

BACKGROUND

The association between ambient temperature and mortality has yielded inconclusive results with previous studies relying on in-patient data to assess the health effects of temperature. Therefore, we aimed to estimate the effect of ambient temperature on non-accidental mortality among elderly hypertensive patients through a prospective cohort study conducted in northeastern China.

METHODS

A total of 9634 elderly hypertensive patients from the Kailuan research who participated in the baseline survey and follow-up from January 1, 2006 to December 31, 2017, were included in the study. We employed a Poisson generalized linear regression model to estimate the effects of monthly ambient temperature and temperature variations on non-accidental mortality.

RESULTS

After adjusting for meteorological parameters, the monthly mean temperature (RR = 0.989, 95% CI: 0.984-0.993, p < 0.001), minimum temperature (RR = 0.987, 95% CI: 0.983-0.992, p < 0.001) and maximum temperature (RR = 0.989, 95% CI: 0.985-0.994, p < 0.001) exhibited a negative association with an increased risk of non-accidental mortality. The presence of higher monthly temperature variation was significantly associated with an elevated risk of mortality (RR = 1.097, 95% CI:1.051-1.146, p < 0.001). Further stratified analysis revealed that these associations were more pronounced during colder months as well as among male and older individuals.

CONCLUSIONS

Decreased temperature and greater variations in ambient temperature were observed to be linked with non-accidental mortality among elderly hypertensive patients, particularly notable within aging populations and males. These understanding regarding the effects of ambient temperature on mortality holds clinical significance for appropriate treatment strategies targeting these individuals while also serving as an indicator for heightened risk of death.

Seasonal variation in blood pressure: what is still missing?

Seasonal variation of blood pressure (BP) is a topic in cardiology that has gained more attention throughout the years. Although it is extensively documented that BP increases in seasons coupled with lower temperatures, there are still many gaps in this knowledge field that need to be explored. Notably, seasonal variation of BP phenotypes, such as masked and white coat hypertension, and the impact of air pollution, latitude, and altitude on seasonal variation of BP are still poorly described in the literature, and the levels of the existing evidence are low. Therefore, further investigations on these topics are needed to provide robust evidence that can be used in clinical practice.

Ambient temperature and ambulatory blood pressure: An hourly-level, longitudinal panel study

BACKGROUND

Variations of blood pressure (BP) related to air temperature have been reported previously; however, no evidence is available regarding the association of hourly ambient temperature with ambulatory blood pressure.

METHODS

We conducted a longitudinal panel study among 1895 patients from an outpatient department who received repeated ambulatory blood pressure monitoring in Urumqi, China between July 2020 and December 2021. We obtained hourly ambient temperature from the nearest monitoring station to the residential address, and measured 4 ambulatory blood pressure indicators. Linear mixed-effect model combined with distributed lag models were applied to investigate the cumulative associations of hourly temperature with BP.

RESULTS

A total of 97,466 valid blood pressure measurements were evaluated. We observed almost linear and monotonically decreasing relationships between temperature and blood pressure. The effects occurred in the same hour, attenuated thereafter and became insignificant approximately 36 h. A 10 °C decrease in temperature was significantly associated with increments of 0.84 mmHg in systolic blood pressure, 0.56 mmHg in diastolic blood pressure, 1.38 mmHg in mean arterial pressure, and 0.66 mmHg in pulse pressure over lag 0 to 36 h. Stronger associations were found among patients of female sex, age between 18 and 65 years, overweight or obesity, minority, less education or in the cold season, as well as those without hypertension or with coronary heart disease, or did not take anti-hypertension medication.

CONCLUSION

Our study provides robust evidence that hourly ambient temperature is inversely associated with ambulatory blood pressure. It also highlights a linear relationship between decreased ambient temperature and elevated BP, which may have implications for the prevention and management of hypertension in susceptible populations.

Seasonal variation in the effect of antihypertensive treatment with the irbesartan/hydrochlorothiazide combination

There is increasing awareness of seasonal variation in blood pressure (BP). In the present analysis, we investigated seasonal variation in the antihypertensive treatment effect of the irbesartan/hydrochlorothiazide combination in patients with stage 2 and 3 hypertension. The study participants were hypertensive patients enrolled in a 12-week therapeutic study. Antihypertensive treatment was initiated with irbesartan/hydrochlorothiazide 150/12.5 mg/day, with possible uptitration to 300/12.5 mg/day and 300/25 mg/day at 4 and 8 weeks of follow-up, respectively. The month of treatment commencement was classified as spring/summer (May to August) and autumn/winter (September to December). Of the 501 enrolled patients, 313 and 188 commenced antihypertensive treatment in spring/summer and autumn/winter, respectively. The mean changes in systolic/diastolic BP at 8 and 12 weeks of follow-up were greater in patients who commenced treatment in autumn/winter (-32.3/-16.5 and -34.2/-16.7 mmHg, respectively) than those who commenced treatment in spring/summer (-28.4/-13.9 and -27.1/-12.8 mmHg, respectively), with a between-season difference of 3.9 (95% confidence interval [CI], 1.4-6.4, P = 0.002)/2.6 (95% CI, 0.9-4.2, P = 0.002) mmHg and 7.0 (95% CI, 4.7-9.3, P < 0.0001)/3.9 (95% CI, 2.4-5.4, P < 0.0001) mmHg, respectively. Further subgroup analyses according to several baseline characteristics showed a greater between-season difference in the changes in systolic BP in patients aged ≥55 years than in those <55 years (n = 255, 12.6 mmHg vs. n = 246, 6.9 mmHg, P = 0.02), especially in patients who did not use antihypertensive medication at baseline (n = 94, 15.4 mmHg vs. n = 132, 5.4 mmHg, P = 0.006). In conclusion, there is indeed seasonality in the antihypertensive treatment effect, with a greater BP reduction in patients who commenced treatment in cold than warm seasons.

Environment and chronic disease in rural areas of Heilongjiang, China (ECDRAHC)

PURPOSE

Environmental factors such as long-term exposure to cold can increase the risk of chronic diseases. However, few studies have focused on the impact of environmental factors and lifestyle changes on chronic diseases. To fully explore the association between exposure to environmental factors and the prevalent risk of various chronic diseases, we conducted a large cohort study (Environment and Chronic Disease in Rural Areas of Heilongjiang, China (ECDRAHC)). The ECDRAHC collected detailed questionnaire data covering 10 sections, physical measurements and blood and urine samples. In this study, we describe the design and implementation of the cohort study and present the findings for the first 10 000 participants.

PARTICIPANTS

The ECDRAHC study was carried out in rural areas where the annual average temperature is 2.9°C, and aimed to recruit 40 000 participants who are long-term residents aged 35-74 years. The participants will be followed up every 5 years. Currently, ECDRAHC has reached 26.7% (n=10 694) of the targeted population.

FINDINGS TO DATE

A total of 10 694 adults aged 35-74 years were recruited, including 61.7% women. The prevalence of current smokers was 46.8% in men and 35.4% in women. The mean blood pressure was 140.2/89.9 mm Hg and 135.7/85.0 mm Hg in men and women, respectively. The mean body mass index was 24.74 kg/m² in men and 24.65 kg/m² in women, with >7.3% being obese (>30 kg/m²). The main non-communicable diseases found in phase 1 were hypertension, diabetes, hypertriglyceridaemia and metabolic syndrome, with a higher prevalence of 51.0%, 21.6%, 46.8% and 42.6%, respectively.

FUTURE PLANS

We plan to complete the follow-up for the first phase of the ECDRAHC in 2024. The second and third phase of the cohort will be carried out steadily, as planned. This cohort will be used to investigate the relationship between environmental factors, lifestyle, and genetic and common chronic diseases.

Ambient Temperature and Cardiac Biomarkers: A Meta-Analysis

This study quantified the effect of cold or heat exposure of ambient temperature on the alteration of well-known cardiac markers. A meta-analysis was performed using the PRISMA guidelines. Peer-reviewed studies on ambient temperature and cardiac biomarkers were retrieved from MEDLINE, ScienceDirect and Google Scholar from January 2000 to February 2022. The pooled effect sizes of ambient temperature on cardiac biomarkers c-reactive protein, soluble-cell adhesion-molecule-1, soluble-intercellular-adhesion-molecule-1, total cholesterol, low-densitylipoprotein, interleukin-6, B-type-Natriuretic-Peptide; systolic/diastolic blood pressure were quantified using a random-effects meta-analysis. A total of 26 articles were included in the metaanalysis after screening the titles, abstracts and full texts. The pooled results for a 1°C decrease of ambient temperature showed an increase of 0.31% (95% CI= 0.26 to 0.38) in cardiac biomarkers (p=0.00; I-squared=99.2%; Cochran's Q=5636.8). In contrast, the pooled results for a 1°C increase in ambient temperature showed an increase of 2.03% (95% CI= 1.08 to 3.82) in cardiac biomarkers (p=0.00; I-squared=95.7%; Cochran's Q=235.2). In the cardiovascular (CV) population, the percent increase in cardiac biomarkers levels due to a decrease/increase in ambient temperature was greater. This study showed the decrease/increase in ambient temperature has a direct correlation with the alterations in cardiac biomarkers. These findings are useful for managing temperatureassociated cardiovascular mortality.

Short-term effects of personal exposure to temperature variability on cardiorespiratory health based on subclinical non-invasive biomarkers

Growing literatures have explored the cardiorespiratory health effects of the daily temperature, but such effects of temperature variability remain unclear. We investigated the acute associations of personal levels of temperature variability with cardiorespiratory biomarkers. This is a panel study with four repeated measurements among forty eligible college students in Hefei, Anhui Province, China. We collected personal-level temperature data using temperature/humidity data loggers. Temperature variability parameters included diurnal temperature range (DTR), the standard-deviation of temperature (SDT) and temperature variability (TV). Cardiorespiratory health indicators included three BP parameters [systolic BP (SBP), diastolic BP (DBP) and mean article pressure (MAP)], fractional exhaled nitric oxide (FeNO), and four saliva biomarkers [C-reactive protein (CRP), cortisol, alpha-amylase and lysozyme]. Linear mixed-effect models were then used to assess the associations of temperature variability with these cardiorespiratory biomarkers. We found that short-term exposure to the three temperature variability parameters was associated with these cardiorespiratory biomarkers. The magnitude, direction and significance of these associations varied by temperature variability parameters, by biomarkers and by lags of exposure. Specifically, temperature variability parameters were inversely associated with BP and saliva lysozyme; positively associated with airway inflammation biomarkers (FeNO and saliva CRP) and stress response biomarkers (saliva cortisol and alpha-amylase). The results were robust to further control for air pollutants, and these associations were more prominent in females and in subjects with abnormal body mass index. Our findings suggested that acute exposure to temperature variability could significantly alter cardiorespiratory biomarker profiles among healthy young adults in China.

Low ambient temperature as a novel risk factor of oral diseases: A time-series study

BACKGROUND

The seasonal variation of oral diseases has been observed in life, but the influences of oral diseases associated with non-optimal ambient temperature were unknown.

OBJECTIVE

To examine whether non-optimum ambient temperature is associated with increased risks of oral diseases.

METHODS

We conducted a time series study based on outpatient data from the Shanghai Health Information Center, containing all public hospitals in Shanghai from 2016 to 2019. Generalized additive models with distributed lagged nonlinear models were applied to fit the data.

RESULT

A total of 3,882,636 outpatient cases of oral diseases were collected. Low temperature (<7 °C) posed increased risks for oral diseases. Daily temperature above 7 °C had no effect on oral diseases. The excess risks were present on the lag 1 day and lasted till lag 7 day. Relative to referent temperatures, the cumulative risks of total oral diseases, pulpitis, periodontitis, gum pain, stomatitis, and glossitis at extreme low temperature (-3 °C, 1st percentile) over lag 0-7 day were 1.92 (95% confidence interval, CI: 1.40, 2.63), 2.40 (95% CI: 1.78, 3.25), 1.62 (95% CI: 1.15, 2.29), 1.75 (95% CI: 1.08, 2.83), 1.81 (95% CI: 1.30, 2.53), and 2.22 (95% CI: 1.23, 3.99). These associations were larger in patients who were above age 60.

CONCLUSION

This study provided novel epidemiological evidence that low ambient temperature may increase the risks of oral diseases. The temperature thresholds for eight oral diseases range from 3 to 7 °C. The excess risks could last for 7 days and were larger in older patients.

The effect of ambient temperature on blood pressure of patients undergoing hemodialysis in the Pantanal-Brazil

The objective was to analyze the association of changes in pre-dialysis systolic and diastolic blood pressure with air temperature in a municipality in the Brazilian Pantanal, a tropical climate area. Longitudinal panel study, with analysis of mixed effects models of 133 hemodialysis patients in the city of Cáceres-Mato Grosso in 2014. Air temperature showed an inverse association with pre-dialysis systolic and diastolic blood pressure. With each increase of 1 °C in the mean air temperature, the pre-dialysis systolic blood pressure decreases -0.730mmHg (p ≤ 0.000) and the pre-dialysis diastolic blood pressure decreases -0.280mmHg (p ≤ 0.000). The estimated effect was greater for systolic blood pressure, but both pre-dialysis blood pressure measures are reduced with an increase in lag (up to two days), even when adjusted for relative air humidity. Air temperature is determinant for changes in pre-dialysis systolic and diastolic blood pressure in hemodialysis patients. The temperature effect was greater for systolic blood pressure than for diastolic blood pressure.

The effect of diurnal temperature range on blood pressure among 46,609 people in Northwestern China

BACKGROUND

A large number of studies have found a positive association between diurnal temperature range (DTR) and cardiovascular diseases (CVDs) incidence and mortality. Few studies regarding the effects of DTR on blood pressure (BP) are available.

OBJECTIVE

To investigate the effects of DTR on BP in Jinchang, northwestern China.

METHODS

Based on a prospective cohort research, a total of 46,609 baseline survey data were collected from 2011 to 2015. The meteorological observation data and environmental monitoring data were collected in the same period. The generalized additive model (GAM) was used to estimate the relationship between DTR and BP after adjusting for confounding variables.

RESULTS

Our study found that there was a positive linear correlation between DTR and systolic blood pressure (SBP) and plus pressure (PP), and a negative linear correlation between DTR and diastolic blood pressure (DBP). With a 1 °C increase of DTR, SBP and PP increased 0.058 mmHg (95%CI: 0.018-0.097) and 0.114 mmHg (95%CI: 0.059-0.168) respectively, and DBP decreased 0.039 mmHg (95%CI:-0.065 ~ -0.014). There was a significant interaction between season and DTR on SBP and PP. DTR had the greatest impact on SBP and PP in hot season. The association between DTR and BP varied significantly by education level.

CONCLUSION

There was a significant association between DTR and BP in Jinchang, an area with large temperature change at high altitudes in northwestern China. These results provide new evidence that DTR is an independent risk factor for BP changes among general population. Therefore, effective control and management of BP in the face of temperature changes can help prevent CVDs.

Acute effects of temperature exposure on blood pressure: An hourly level panel study

BACKGROUND

Several epidemiological studies have shown that blood pressure changes with temperature based on the daily temperature and linear relationship assumption. However, little is known about the true curve shape of the relationship between temperature and blood pressure.

OBJECTIVES

The objective of this study was to investigate the non-linear relationship between hourly temperature and blood pressure.

METHODS

This is a prospective panel study comprising 100 participants in Suzhou, China. The blood pressure of each participant was measured >50 times between October 2013 and January 2016. Hourly temperature data were derived from the nearest monitoring station owned by the China Meteorological Administration. A Distributed Lag Nonlinear Model (DLNM) was used to investigate the relationship between hourly temperature and blood pressure.

RESULTS

We found that the relationship between hourly temperature and blood pressure was parabolic. Short-term exposure to hourly temperatures had significant cold and heat effects on systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure (PP), and mean arterial pressure (MAP). The hourly temperature had a significant lag effect on blood pressure, with a lag time of 0-5 h. Alcohol users were more sensitive to the cold effects of hourly temperature, and the diabetic population was more sensitive to the heat effects of hourly temperature on PP.

CONCLUSION

Temperature imparts short-term effects on blood pressure. Therefore, timely protective measures during cold waves or cold weather are beneficial to maintain stable blood pressure levels to reduce the risk of blood pressure related diseases.

The short-term effects of outdoor temperature on blood pressure among children and adolescents: finding from a large sample cross-sectional study in Suzhou, China

Although several studies have demonstrated a short-term association between outdoor temperature and blood pressure (BP) among various adult groups, evidence among children and adolescents is lacking. One hundred ninety-four thousand one hundred four participants from 2016 Health Promotion Program for Children and Adolescents (HPPCA) were analyzed through generalized linear mixed-effects models to estimate the short-term effects of two outdoor temperature variables (average and minimum temperature) on participants' BP. Decreasing outdoor temperature was associated with significant increases in systolic BP (SBP), diastolic BP (DBP), and prevalence of hypertension during lag 0 through lag 6. Additionally, daily minimum temperature showed a more apparent association with participants' BP. The estimated increases (95% confidence interval) in SBP and DBP at lag 0 were 0.82 (0.72, 0.92) mmHg and 2.28 (2.20, 2.35) mmHg for a 1 °C decrease in daily minimum temperature, while those values were 0.11 (0.10, 0.12) mmHg and 0.25 (0.24, 0.26) mmHg for a 1 °C decrease in daily average temperature, respectively. The effects of temperature on BP were stronger among female, as well as those with young age and low body mass index. It demonstrated that short-term decreases in outdoor temperature were significantly associated with rises in BP among children and adolescents. This founding has some implications for clinical management and research of BP. Meanwhile, public health intervention should be designed to reduce the exposure to cold temperature for protecting children and adolescents' BP.

Short-term effects of air temperature on plasma metabolite concentrations in patients undergoing cardiac catheterization

BACKGROUND

Epidemiological studies have shown associations between air temperature and cardiovascular health outcomes. Metabolic dysregulation might also play a role in the development of cardiovascular disease.

OBJECTIVES

To investigate short-term temperature effects on metabolites related to cardiovascular disease.

METHODS

Concentrations of 45 acylcarnitines, 15 amino acids, ketone bodies and total free fatty acids were available in 2869 participants from the CATHeterization GENetics cohort recruited at the Duke University Cardiac Catheterization Clinic (Durham, NC) between 2001 and 2007. Ten metabolites were selected based on quality criteria and cluster analysis. Daily averages of meteorological variables were obtained from the North American Regional Reanalysis project. Immediate, lagged, and cumulative temperature effects on metabolite concentrations were analyzed using (piecewise) linear regression models.

RESULTS

Linear temperature effects were found for glycine, C16-OH:C14:1-DC, and aspartic acid/asparagine. A 5°C increase in temperature was associated with a 1.8% [95%-confidence interval: 0.3%; 3.3%] increase in glycine (5-day average), a 3.2% [0.1%; 6.3%] increase in C16-OH:C14:1-DC (lag of four days), and a -1.4% [-2.4%; -0.3%] decrease in aspartic acid/asparagine (lag of two days). Non-linear temperature effects were observed for alanine and total ketone bodies with breakpoint of 4°C and 20°C, respectively. Both a 5°C decrease in temperature on colder days (<4°C)and a 5°C increase in temperature on warmer days (≥4°C) were associated with a four day delayed increase in alanine by 6.6% [11.7; 1.8%] and 1.9% [0.3%; 3.4%], respectively. For ketone bodies we found immediate (0-day lag) increases of 4.2% [-0.5%; 9.1%] and 12.3% [0.1%; 26.0%] associated with 5°C decreases on colder (<20°C) days and 5°C increases on warmer days (≥20°C), respectively.

CONCLUSIONS

We observed multiple effects of air temperature on metabolites several of which are reported to be involved in cardiovascular disease. Our findings might help to understand the link between air temperature and cardiovascular disease.