Seasonal variation of blood pressure in normotensive females aged 18 to 40 years in an urban slum of Delhi, India

Dwelling Characteristics Influence Indoor Temperature and May Pose Health Threats in LMICs

Background:

Shelter and safe housing is a basic human need that brings about a sense of ownership, self-sufficiency, and citizenship. Millions of people around the world live in inadequate dwellings in unhealthy areas, such as urban slums. These dwellings may experience indoor temperatures that impact inhabitants’ health. Indoor dwelling temperatures vary depending on many factors including geographic location, such as inland versus coastal. In an era of climate change, understanding how dwelling characteristics influence indoor temperature is important, especially in low- and middle-income countries, to protect health.

Objective:

To assess indoor temperature in low-cost dwellings located in a coastal setting in relation to dwelling characteristics.

Methods:

Indoor temperature and relative humidity loggers were installed from 1 June 2017 to 15 May 2018 in 50 dwellings in two settlements in a coastal town on the east coast of South Africa. Ambient outdoor temperature data were obtained from the national weather service, indoor temperature data were converted into apparent temperature, and heat index calculations were made to consider possible heat-health risks. A household questionnaire and dwelling observation assessment were administered. A mixed-effects linear regression model was constructed to consider the impact of dwelling characteristics on indoor apparent temperature.

Findings:

Among 17 dwellings with all data sets, indoor temperatures were consistently higher than, and well correlated (r = 0.92) with outdoor temperatures. Average differences in indoor and outdoor temperatures were about 4°C, with statistically significant differences in percentage difference of indoor/outdoor between seasons (p < 0.001). Heat indices for indoor temperatures were exceeded mostly in summer, thereby posing possible health risks. Dwellings with cement floors were statistically significantly cooler than any other floor type across all seasons.

Conclusions:

Low-cost dwellings experienced temperatures indoors higher than outdoor temperatures in part due to floor type. These results help inform interventions that consider housing and human health (n = 289).

'My blood pressure is low today, do you have the heating on?' The association between indoor temperature and blood pressure

OBJECTIVES

The independent association of indoor temperature with blood pressure (BP) is poorly understood and is not routinely considered in hypertension diagnosis or research. Questions remain as to whether the effect of indoor temperature on BP is confounded or modified by other factors.

METHODS

This study used data from the Health Survey for England 2014, consisting of 4659 community-dwelling adults aged 16 years and over, interviewed from January to December. Multivariable regression models were used to determine whether indoor temperature was related to levels of BP, and whether these relationships were confounded by other factors, including mean monthly outdoor temperature.

RESULTS

After controlling for confounding variables, a 1°C decrease in indoor temperature was associated with rises of 0.48 mmHg (95% confidence interval: -0.72 to -0.25) in SBP and 0.45 mmHg (95% confidence interval: -0.63 to -0.27) in DBP. The magnitude of association of indoor temperature with DBP and SBP was modified by physical activity. The indoor temperature-BP relationship was stronger in people who do not take physical activity regularly than people who exercise regularly.

CONCLUSION

The size of the independent association between indoor temperature and BP suggests it should be considered in the clinical management of hypertension and in hypertension research. Room temperature should also be considered as a modifiable risk factor in hypertension-related mortality and morbidity.

Vitamin D Receptor Deficiency Does Not Affect Blood Pressure and Heart Function

Vitamin D is thought to play a role in blood pressure regulation, which in turn can influence cardiovascular risk. Several meta-analyses of cohort studies found low serum levels of 25-hydroxyvitamin D to be associated with increased blood pressure or increased cardiovascular morbidity and mortality in the general population. Active vitamin D mediates its function via the vitamin D receptor (Vdr), which is a ligand-activated transcription factor. A suitable model to examine the causal role of vitamin D in blood pressure regulation and heart function is the Vdr knockout (Vdr^–/–) mouse. To elucidate the role of vitamin D on blood pressure, heart function, and cardiac myocyte size, we conducted a long-term study using Vdr^–/– mice and well-defined diets. Group 1 comprised Vdr^–/– mice that received a high-calcium, high-phosphorus rescue diet to prevent hypocalcemia and a rickets phenotype. Groups 2 and 3 included Vdr^+/+ mice that were fed either the rescue diet or a control diet containing normal amounts of these minerals. As Vdr is a nuclear factor that regulates transcription, we analyzed the renal mRNA expression and serum concentration of renin and found that the Vdr^–/– group had an almost 50% higher renin mRNA expression in the kidney compared to both groups of Vdr^+/+ mice. Additionally, serum concentration of renin in Vdr^–/– mice was significantly higher than that of Vdr^+/+ mice that received the rescue or control diet (+ 17%,+ 32%; P < 0.05). In contrast, renin activity was lower in Vdr^–/– mice than in both groups of Vdr^+/+ mice (P < 0.05). However, blood pressure, heart rate, cardiac myocyte sizes, and the expression of renal renin receptor, hepatic angiotensinogen and angiotensin II receptor, type 1, in kidney, liver and heart, did not differ between the three groups of mice. Additionally, data from transthoracic echocardiography did not indicate the role of Vdr on heart function, as the left ventricular ejection fraction, fractional shortening, and velocity of blood flow were comparable between the three groups. To conclude, the roles of Vdr and therefore most probably of vitamin D, in blood pressure regulation and heart function, were not confirmed by our findings.

Variation of indoor minimum mortality temperature in different cities: Evidence of local adaptations

Epidemiological studies on the impact of outdoor temperature to human health have demonstrated the capability of humans to adapt to local climate. However, there is limited information on the association between indoor temperature and human health, despite people spending most of their time indoors. The problem stems from the lack of sufficient indoor temperature measurement in the population. To overcome this obstacle, this paper presents an indirect epidemiological approach to evaluate the impact of high indoor temperature on mortality. The relationships between indoor-outdoor temperatures in different climate zones identified in the literature were combined with the outdoor temperature-mortality curves of the same locations to obtain the local indoor minimum mortality temperatures (iMMT), the temperature at which mortality is lowest, which by implication is the temperature at which the population is most comfortable on average. We show that the iMMT varies and has a weak linear relationship with the distance to the equator, which provides evidence of human adaptation to local indoor temperatures. These findings reinforce the adaptive comfort theory, which states that people can adapt to local indoor environment and establish their thermal comfort. Recognising the human adaptability to local climate will direct flexible and optimized policy to protect public health against extreme temperature events. This will also help reduce energy consumption for regulating indoor temperature without compromising the occupants' health.

The Association between Serum 25(OH)D Status and Blood Pressure in Participants of a Community-Based Program Taking Vitamin D Supplements

Background: Vitamin D deficiency is a risk factor for hypertension. Methods: We assessed 8155 participants in a community-based program to investigate the association between serum 25-hydroxyvitamin D (25(OH)D) status and blood pressure (BP) and the influence of vitamin D supplementation on hypertension. Participants were provided vitamin D supplements to reach a target serum 25(OH)D > 100 nmol/L. A nested case-control study was conducted to examine the effect of achieving physiological vitamin D status in those who were hypertensive and not taking BP-lowering medication, and hypertensive participants that initiated BP-lowering medication after program entry. Results: At baseline, 592 participants (7.3%) were hypertensive; of those, 71% were no longer hypertensive at follow-up (12 ± 3 months later). There was a significant negative association between BP and serum 25(OH)D level (systolic BP: coefficient = −0.07, p < 0.001; diastolic BP: coefficient = −0.1, p < 0.001). Reduced mean systolic (−18 vs. −14 mmHg) and diastolic (−12 vs. −12 mmHg) BP, pulse pressure (−5 vs. −1 mmHg) and mean arterial pressure (−14 vs. −13 mmHg) were not significantly different between hypertensive participants who did and did not take BP-lowering medication. Conclusion: Improved serum 25(OH)D concentrations in hypertensive individuals who were vitamin D insufficient were associated with improved control of systolic and diastolic BP.

Effects of outdoor temperature on changes in physiological variables before and after lunch in healthy women

Previous studies of autonomic nervous system responses before and after eating when controlling patient conditions and room temperature have provided inconsistent results. We hypothesized that several physiological parameters reflecting autonomic activity are affected by outdoor temperature before and after a meal. We measured the following physiological variables before and after a fixed meal in 53 healthy Japanese women: skin temperature, systolic and diastolic blood pressure, salivary amylase, blood glucose, heart rate, and heart rate variability. We assessed satiety before and after lunch using a visual analog scale (100 mm). We recorded outdoor temperature, atmospheric pressure, and relative humidity. Skin temperature rose significantly 1 h after eating (greater in cold weather) (P = 0.008). Cold weather markedly influenced changes in diastolic blood pressure before (P = 0.017) and after lunch (P = 0.013). Fasting salivary amylase activity increased significantly in cold weather but fell significantly after lunch (significantly greater in cold weather) (P = 0.007). Salivary amylase was significantly associated with cold weather, low atmospheric pressure, and low relative humidity 30 min after lunch (P < 0.05). Cold weather significantly influenced heart rate variability (P = 0.001). The decreased low frequency (LF)/high frequency (HF) ratio, increased Δ LF/HF ratio, and increased Δ salivary amylase activity imply that cold outdoor temperature is associated with dominant parasympathetic activity after lunch. Our results clarify the relationship between environmental factors, food intake, and autonomic system and physiological variables, which helps our understanding of homeostasis and metabolism.

Derivation and validation of BOREAS, a risk score identifying candidates to develop cold-induced hypertension

INTRODUCTION

Blood pressure increases in cold periods, but its implications on prevalence of hypertension and on individual progression to hypertension remain unclear. Our aim was to develop a pre-screening test for identifying candidates to suffer hypertension only in cold months among non-hypertensive subjects.

METHODS

We included 95,277 subjects registered on a primary care database from Girona (Catalonia, Spain), with ≥ 3 blood pressure measures recorded between 2003 and 2009 and distributed in both cold (October-March) and warm (April-September) periods. We defined four blood pressure patterns depending on the presence of hypertension through these periods. A Cox model determined the risk to develop vascular events associated with blood pressure patterns. A logistic regression distinguished those nonhypertensive individuals who are more prone to suffer cold-induced hypertension. Validity was assessed on the basis of calibration (using Brier score) and discrimination (using the area under the receiver operating characteristics).

RESULTS

In cold months, the mean systolic blood pressure increased by 3.3 ± 0.1 mmHg and prevalence of hypertension increased by 8.2%. Cold-induced hypertension patients were at higher vascular events risk (Hazard ratio=1.44 [95% Confidence interval 1.15-1.81]), than nonhypertensive individuals. We identified age, diabetes, body mass index and prehypertension as the major contributing factors to cold-induced hypertension onset.

DISCUSSION

Hypertension follows a seasonal pattern in some individuals. We recommend screening for hypertension during the cold months, at least in those nonhypertensive individuals identified as cold-induced hypertensive by this assessment tool.

Influence of seasonal variation on blood pressure measurements in children, adolescents and young adults

BACKGROUND

Seasonal fluctuations in outdoor temperature have been shown to affect blood pressure in adults. The aim of our study was to determine whether blood pressure measurements in children and adolescents in Central Europe undergo seasonal variation or are influenced by outdoor temperature.

METHODS

The blood pressure of 6,714 subjects (3,497 boys, 3,237 girls) aged 3 to 21 (median age 10.6) years was routinely measured. The study cohort comprised both healthy and sick children and adolescents visiting outpatient clinics and during hospitalisation.

RESULTS

Cross-sectional analysis showed a significant seasonal variation in blood pressure measurements. The mean increase of systolic/diastolic blood pressure was 4.45/2.42 mmHg during the winter. A significant correlation between average outdoor temperature and systolic blood pressure was found (ρ = -0.074 p < 0.001). However, the effect was only detectable at an average temperature below 0 °C/32 °F and above 10 °C/50 °F. For each 1 °C increase in average outdoor temperature, the systolic blood pressure fell by 0.12 mmHg.

CONCLUSIONS

Blood pressure measurements in children and adolescents, even in a temperate climate, are influenced by temperature and subject to seasonal variation. Considering seasonal variations in blood pressure could be of clinical interest.

Seasonal variation in blood pressure is modulated by gender and age but not by BMI in a large Taiwanese population, 1996-2006

Previous research has found that blood pressure tends to be higher in winter and lower in summer. The present study examined seasonal variation in blood pressure by gender, hypertension medication, age group, and body mass index using contemporary Taiwanese data. Over 400,000 health screening records collected biennially between 1996 and 2006 were used to calculate average monthly systolic (SBP) and diastolic blood pressure (DBP) measurements. Generalized estimating equations were used to estimate the difference between the highest and lowest mean monthly blood pressure measurements. Mean monthly blood pressure measurements were higher in winter than in summer for all age groups, regardless of medication for hypertension. The largest difference in mean monthly blood pressure between summer and winter months was 5.3 mm Hg (Standard error = 0.7) for SBP and 3.2 mm Hg (Standard error = 0.7) for DBP. These differences were more pronounced: in SBP than in DBP; in men than in women; and in older than in younger participants. Body mass index was not clearly associated with seasonal variation in blood pressure. Seasonal variation in blood pressure among contemporary Taiwanese populations is modest and may only approach clinical significance for the diagnosis and treatment of hypertension and the prevention of cardiovascular disease amongst older male individuals.

Seasonal changes in blood pressure: Cardiac and cerebrovascular morbidity and mortality

Cold is a seasonal and circadian risk factor for cardio- and cerebrovascular morbidity and mortality. Colder temperatures have been associated with higher blood pressure (BP), based on studies which show that BP levels measured during the summer months are generally lower than those measured during the winter months. Residents in geographic areas which have greater seasonal temperature differences show greater fluctuation in BP. Surprisingly, atmospheric pressure, rainfall, and humidity were not related to BP levels. The increased sympathetic nervous activity due to cold, as evidenced by elevated BP and by plasma and urinary catecholamines, has been proposed as being the underlying etiology. Patients with heart failure may experience, in cold conditions, endothelial dysfunction and produce fewer endogenous vasodilators (e.g., nitric oxide, prostaglandins) and more endogenous vasoconstrictors (e.g., endothelin), thus increasing afterload. Arterial stiffness is also related to seasonal BP changes. Increased BP, arterial stiffness and endothelial dysfunction could predispose to increased coronary and cerebrovascular events. Improved protection against lower temperatures or increased doses of existing medications or the addition of newer medications could lead to a reduction in increased cardiovascular mortality in winter. Here, we briefly review findings from existing literature and provide an update on seasonal long-term variation in BP along with the related complications.

Effects of a 6-Month Walking Study on Blood Pressure and Cardiorespiratory Fitness in U.S. and Swedish Adults: ASUKI Step Study

Purpose

The aim of this study was to assess the effects of a six-month pedometer-based workplace intervention on changes in resting blood pressure (BP) and cardiorespiratory fitness (CRF).

Methods

A subsample of ASUKI Step participants (n= 355) were randomly selected to have changes in their BP and CRF monitored during the intervention. Pedometers were used to monitor steps taken with a goal of walking more than 10,000 steps/day. Systolic and diastolic BP were taken using an Omron automated BP cuff. Estimated VO₂ max was obtained using the Åstrand-Rhyming cycle ergometer test. A multi-level growth modeling approach, and a mixed model ANOVA were used to predict changes in systolic and diastolic BP, and estimated VO₂ max over time by steps, age, gender, and university site.

Results

Steps/day averaged 12,256 (SD = 3,180) during month 1 and steadily decreased to month 6. There were significant linear and quadratic trends in systolic and diastolic BP over time. Age was positively related to initial starting values for systolic and diastolic BP, and approached significance for systolic BP changes over time. Steps/day approached significance for linear changes in systolic BP. There was a significant difference between ASU and KI participants’ estimated VO₂ max. There was a significant change over time in the estimated VO₂ max. The number of steps taken was significantly related to changes in estimated VO₂ max over time.

Conclusions

The results of the present study indicate that healthy individuals who took part in a pedometer intervention improved several cardiovascular disease risk factors.

Hypertension with elevated levels of oxidized low-density lipoprotein and anticardiolipin antibody in the circulation of premenopausal Indian women chronically exposed to biomass smoke during cooking

This study aims to investigate whether indoor air pollution (IAP) from biomass fuel use was associated with hypertension, platelet hyperactivity, and elevated levels of oxidized low-density lipoprotein (oxLDL) and anticardiolipin antibody (aCL). We enrolled 244 biomass fuel-using (median age 34 year) and 236 age-matched control women who cooked with liquefied petroleum gas (LPG). Enzyme-linked immunosorbent assay was used to measure oxLDL in plasma and aCL in serum, flow cytometry for P-selectin expression on platelet and reactive oxygen species (ROS) generation by leukocytes, aggregometry for platelet aggregation, spectrophotometry for superoxide dismutase (SOD) in erythrocytes, and laser photometer for particulate matter <10 and 2.5 μm in diameter (PM(10) and PM(2.5), respectively) in cooking areas. Biomass users had three times more particulate pollution in kitchen, had higher prevalence of hypertension (29.5 vs. 11.0% in control, P < 0.05), elevated oxLDL (170.6 vs. 45.9 U/l; P < 0.001), platelet P-selectin expression (9.1% vs. 2.4%), platelet aggregation (23.2 vs. 15.9 Ohm), raised aCL IgG (28.7% vs. 2.1%), IgM (8.6% of vs. 0.4%), and ROS (44%) but depleted (13%) SOD. After controlling potential confounders, the changes were positively associated with PM(10) and PM(2.5) in indoor air, suggesting a positive association between IAP and increased cardiovascular risk.

PRACTICAL IMPLICATIONS

The study showing high risk of developing cardiovascular diseases (CVD) among poor, underprivileged women in their reproductive ages in rural India is important from public health perspectives. It may motivate the government and the regulatory agencies of the country to take a serious note of the indoor air pollution (IAP) from biomass fuel use as it threatens the health of millions of women, children, and the elderly who mostly stay indoor. We hope the findings will strengthen the demand for setting up a standard for indoor air quality in the country in the line of national ambient air quality standard. The findings may also inspire the authorities to take measures for the reduction in IAP by improving housing, kitchen ventilation, and cook stoves. Moreover, the parameters used in this study can be utilized for large, population-based studies to identify women at a higher risk of developing CVD so that medical intervention can be taken at the formative stage of a disease.

Joint prevalence and control of hypercholesterolemia and hypertension in Thailand: third national health examination survey

The prevalence, diagnosis, treatment, and control of hypercholesterolemia and/or hypertension were estimated for Thailand using data from a recent, nationally representative health examination survey. Multivariate logistic regression was used to assess factors associated with diagnosis, treatment, and control. In all, 14% of men and 17% of women had hypercholesterolemia, 23% and 21% had hypertension, and 5% and 6%, respectively, had both. A large proportion of individuals with these risk factors is neither diagnosed nor treated, let alone adequately controlled; 30% of people with hypertension had been diagnosed and 24% treated, and 9% had their blood pressure controlled. The figures for hypercholesterolemia were 13%, 9%, and 6%, respectively. Those for both risk factors combined were below 15% and did not differ by sex, urbanicity, age, or marital status. Among men, education correlated with diagnosis and treatment odds. There is great scope for improved prevention of cardiovascular disease in Thailand.