Seasonal blood pressure variation and its relationship to environmental temperature in healthy elderly Japanese studied by home measurements

Is there any association between the frequency of wet age-related macular degeneration recurrences and the seasons of the year?

PURPOSE

To investigate whether a seasonal distribution of the frequency of exudative age-related macular degeneration (wet AMD) recurrences exists.

METHODS

In total, 129 eyes with 171 recurrences in patients suffering from wet AMD were included in the study. All the patients had been treated with intravitreal anti-VEGF injections according to Pro Re Nata treatment regimen. Recurrence was defined as the re-detection of sub-retinal fluid, intraretinal fluid, and/or sub-macular hemorrhage in optical coherence tomography scans, after at least two consecutive monthly examinations with a "dry" macula. The year was divided in three 4-month periods (zone A: June-September, zone B: October-January, and zone C: February-May) based on the weather conditions prevailing in each period. Mean temperature and hours of sunlight exposure were the main weather markers recorded.

RESULTS

Eighty-two recurrences (48%) occurred during the period June-September, 50 (29.2%) during the period October-January, and 39 (22.8%) during the period February-May (Chi-square = 17.5, p < 0.001). Among the groups, neither patients' age (78 ± 8 years A, 76 ± 7 years B, and 79 ± 8 years C, p = 0.15) nor gender status (40% men A, 36% men B, and 51% men C, p = 0.35) differed significantly. Mean temperature was 27.6 ± 1.8 °C, 15.1 ± 4.6 °C, and 16.5 ± 4.4 °C in zones A, B, and C, respectively. Hours (h) of sunlight exposure (average hours/month) were 344 ± 34 h, 188 ± 42 h, and 223 ± 57 h in zones A, B, and C.

CONCLUSION

We demonstrated that the frequency of wet AMD recurrences is significantly elevated during the warmer months, possibly due to the higher levels of UV radiation and mean temperature. Further research is necessary to validate our findings.

Medical Telemonitoring for the Management of Hypertension in Older Patients in Japan

Hypertension is the most frequent modifiable risk factor associated with cardiovascular disease (CVD) morbidity and mortality. Even in older people, strict blood pressure (BP) control has been recommended to reduce CVD event risks. However, caution should be exercised since older hypertensive patients have increased physical vulnerability due to frailty and multimorbidity, and older patients eligible for clinical trials may not represent the general population. Medical telemonitoring systems, which enable us to monitor a patient's medical condition remotely through digital communication, have become much more prevalent since the coronavirus pandemic. Among various physiological parameters, BP monitoring is well-suited to the use of such systems, which enable healthcare providers to deliver accurate and safe BP management, even in the presence of frailty and/or living in geographically remote areas. Furthermore, medical telemonitoring systems could help reduce nonadherence to antihypertensive medications and clinical inertia, and also enable multi-professional team-based management of hypertension. However, the implementation of medical telemonitoring systems in clinical practice is not easy, and substantial barriers, including the development of user-friendly devices, integration with existing clinical systems, data security, and cost of implementation and maintenance, need to be overcome. In this review, we focus on the potential of medical telemonitoring for the management of hypertension in older people in Japan.

Sources of automatic office blood pressure measurement error: a systematic review

OBJECTIVE

Accurate and reliable blood pressure (BP) measurement is important for the prevention and treatment of hypertension. The oscillometric-based automatic office blood pressure measurement (AOBPM) is widely used in hospitals and clinics, but measurement errors are common in BP measurements. There is a lack of systematic review of the sources of measurement errors.

APPROACH

A systematic review of all existing research on sources of AOBPM errors. A search strategy was designed in six online databases, and all the literature published before October 2021 was selected. Those studies that used the AOBPM device to measure BP from the upper arm of subjects were included.

MAIN RESULTS

A total of 1365 studies were screened, and 224 studies were included in this final review. They investigated 22 common error sources with clinical AOBPM. Regarding the causes of BP errors, this review divided them into the following categories: the activities before measurement, patient's factors, measurement environment, measurement procedure, and device settings. 13 sources caused increased systolic and diastolic BP (SBP and DBP), 2 sources caused the decrease in SBP and DBP, only 1 source had no significant effect on BPs, and the other errors had a non-uniform effect (either increase or decrease in BPs). The error ranges for SBP and DBP were -14 to 33 mmHg and -6 to 19 mmHg, respectively.

SIGNIFICANCE

The measurement accuracy of AOBPM is susceptible to the influence of measurement factors. Interpreting BP readings need to be treated with caution in clinical measurements. This review made comprehensive evidence for the need for standardized BP measurements and provided guidance for clinical practitioners when measuring BP with AOBPM devices.

Impact of weather changes on hospital admissions for hypertension

Blood pressure (BP) shows a seasonal variation with higher levels at lower temperatures. Many hypertensives, however, report on BP disturbances rather in association with acutely changing weather conditions than with absolute temperatures. To date, the impact of changing meteorological parameters on hypertensive episodes remains elusive. We performed a retrospective time series regression analysis on 203,703 patients in three hospitals in Germany between 2010 and 2018, of whom 7362 patients were admitted for hypertensive disease. Numbers of daily admissions for hypertension were associated with metereological data obtained from three nearby weather stations. Data comprised temperature (mean, maximal, minimal and range within 24 h), athmospheric pressure, and precipitation. Changes of these parameters were calculated over a two and three day period. There was an inverse correlation between maximal daily temperature and the number of admissions for hypertensive disease, which remained significant both after adjustment for seasonality and week day in a spline model and in a constrained distributed lag model. A decrease of maximal temperature by 5 °C was associated with a 3% increase of risk for admission for hypertension and vice versa. There were no significant effects of precipitation and athmospheric pressure on the number of admissions. With regard to all observed metereological parameters, neither the change within two, nor within three days was consistently associated with the number of daily admissions. High temperatures are associated with lower numbers of hypertensive episodes requiring hospital admission. In contrast to the subjective perception of many hypertensive patients, however, acutely changing weather conditions are not associated with a higher risk of hypertensive emergency.

Long-term amlodipine-based combination therapy attenuates seasonal variation of blood pressure in hypertensive patients

Objectives: This study was to investigate whether long-term amlodipine-based combination therapy attenuates seasonal variation of office blood pressure (BP) in hypertensive patients. Methods: The data of 206 patients recruited in the Nanchang site of CHIEF trial were retrospectively analyzed. All patients received an amlodipine-based therapy for three years after reaching target BP with a 12-week titration treatment. Among them, 106 patients received amlodipine plus amiloride/hydrochlorothiazide (AA group) and 100 received amlodipine plus telmisartan (AT group) therapies. These patients were followed up every three months . The difference between the highest and lowest values of outdoor temperature in each three months was calculated as the seasonal temperature difference (T-d) and seasonal BP difference was calculated in the similar way. BP control rates in each season were calculated. Results: In the three years, the highest SBP and DBP values occurred in winter and the lowest values in summer. As a result, the BP control rate in summer was the highest and that in winter was the lowest, especially for SBP. Although T-d levels were similar during three following-up years, the seasonal SBP/DBP differences in 2011 were significantly lower than 2009 (10.03 ± 5.74/6.96 ± 3.72 vs 14.36 ± 8.19/9.78 ± 5.21 mmHg, P < .05), suggesting seasonal variation in BP was obviously reduced. Meanwhile, similar change was observed in AA and AT groups. Conclusions: Besides lower BP effectively, long-term amlodipine-based combination therapy could alleviate the seasonal BP variation in high-risk hypertensive patients.

Seasonal variation in blood pressure: current evidence and recommendations for hypertension management

Blood pressure (BP) exhibits seasonal variation, with an elevation of daytime BP in winter and an elevation of nighttime BP in summer. The wintertime elevation of daytime BP is largely attributable to cold temperatures. The summertime elevation of nighttime BP is not due mainly to temperature; rather, it is considered to be related to physical discomfort and poor sleep quality due to the summer weather. The winter elevation of daytime BP is likely to be associated with the increased incidence of cardiovascular disease (CVD) events in winter compared to other seasons. The suppression of excess seasonal BP changes, especially the wintertime elevation of daytime BP and the summertime elevation of nighttime BP, would contribute to the prevention of CVD events. Herein, we review the literature on seasonal variations in BP, and we recommend the following measures for suppressing excess seasonal BP changes as part of a regimen to manage hypertension: (1) out-of-office BP monitoring, especially home BP measurements, throughout the year to evaluate seasonal variations in BP; (2) the early titration and tapering of antihypertensive medications before winter and summer; (3) the optimization of environmental factors such as room temperature and housing conditions; and (4) the use of information and communication technology-based medicine to evaluate seasonal variations in BP and provide early therapeutic intervention. Seasonal BP variations are an important treatment target for the prevention of CVD through the management of hypertension, and further research is necessary to clarify these variations.

Impact of Low Ambient Temperature on the Occurrence of Spontaneous Intracerebral Hemorrhage-Analysis of Population-Based Stroke Registry in Toyama, Japan

OBJECTIVE

Although several studies have reported that some meteorological factors such as ambient temperature and atmospheric pressure, affect the incidence of spontaneous intracerebral hemorrhage (ICH), the correlation remains unclear. This retrospective time-series analysis was aimed to clarify the effects of meteorological parameters on the incidence of ICH.

MATERIALS AND METHODS

Data of patients with ICH were obtained from a population-based survey of acute stroke patients between April 2016 and March 2019. All days during the study period were categorized into "no ICH day" when no ICHs occurred, "single ICH day" when only one ICH occurred, and "cluster day" when two or more ICHs occurred. Meteorological data were compared for among the three categories.

RESULTS

1,691 ICH patients from 19 hospitals were registered. In a total of 1,095 days, 250 were categorized as no ICH days, 361 as single ICH days, and 484 as cluster days. Daily ambient temperature declined in parallel with the daily number of ICHs, and it was a significant predictor for single ICH days and cluster days. Furthermore, the incidence of ICH in patients aged 65 years or above, men, those who emerged at home, those with modified Rankin Scale 3-5; and those with hypertension; and ICHs in the basal ganglia, brain stem, and cerebellum were more likely to be affected by low ambient temperature.

CONCLUSION

Daily ambient temperature was significantly associated with ICH incidence. Patients' activity, history of hypertension, and location of hemorrhage were also related to the impact of low ambient temperature on the incidence of ICH.

Effects of seasonal and climate variations on in-hospital mortality and length of stay in patients with type A aortic dissection

Objective

To investigate the effects of seasonal and climatic changes on postoperative in-hospital mortality and length of stay (LOS) in patients with type A acute aortic dissection (AAD).

Methods

Patients undergoing implantation of the modified triple-branched stent graft to replace the descending aorta in addition to aortic root reconstruction for type A AAD in our hospital from January 2016 to December 2019 were included. Relevant data were retrospectively collected and analyzed.

Results

A total of 404 patients were included in our analyses. The multivariate unconditional logistic regression analysis showed that patients admitted in autumn (OR 4.027, 95% CI 1.023–17.301, P = 0.039) or with coronary heart disease (OR 8.938, 95% CI 1.991–29.560, P = 0.049) were independently associated with an increased risk of postoperative in-hospital mortality. Furthermore, patients admitted in autumn (OR 5.956, 95% CI 2.719–7.921, P = 0.041) or with hypertension (OR 3.486, 95% CI 1.192–5.106, P = 0.035) were independently associated with an increased risk of longer LOS.

Conclusion

Patients admitted in autumn or with coronary heart disease are at higher risk of in-hospital mortality following surgery for type A AAD. Also, patients admitted in autumn or with hypertension have a longer hospital LOS. In the autumn of the temperature transition, we may need to strengthen the management of medical quality after surgery for type A AAD.

Association between Physical Activity and Seasonal Variations in Metabolic and Vascular Function in Adults

This article highlights the association between physical activity (PA) and seasonal variations in metabolic and vascular function in adults. Increasing PA is an important method for preventing cardiovascular disease (CVD) and all-cause mortality by improving blood glucose, blood pressure, blood lipid profiles, body fat, insulin resistance, and vascular function, such as endothelial function. Conversely, various factors, such as seasonal climate conditions, may affect the amount of PA that individuals undertake. Changes in PA often induce seasonal variations in metabolic and vascular function; the deterioration of such functions in winter is the most prominent, and there is clear evidence of an increased risk of CVD in this season. Understanding the influence of PA on seasonal variations observed in metabolic and vascular function is necessary for the management of these physiological functions. In this article summary, few studies have proven that maintaining PA can suppress the variations, and it remains unclear what types, intensities, and durations of regular PA are effective for circumventing seasonal impact. In addition to further studies, there is a need to educate individuals about the strategies to manage PA and other aspects of their lifestyles throughout the year, particularly in winter.

Assessment of the Relationship Between Ambient Temperature and Home Blood Pressure in Patients From a Web-Based Synchronous Telehealth Care Program: Retrospective Study

BACKGROUND

Decreased ambient temperature significantly increases office blood pressure, but few studies have evaluated the effect of ambient temperature on home blood pressure.

OBJECTIVE

We aimed to investigate the relationship between short-term ambient temperature exposure and home blood pressure.

METHODS

We recruited patients with chronic cardiovascular diseases from a telehealth care program at a university-affiliated hospital. Blood pressure was measured at home by patients or their caregivers. We obtained hourly meteorological data for Taipei (temperature, relative humidity, and wind speed) for the same time period from the Central Weather Bureau, Taiwan.

RESULTS

From 2009 to 2013, we enrolled a total of 253 patients. Mean patient age was 70.28 (SD 13.79) years, and 66.0% (167/253) of patients were male. We collected a total of 110,715 home blood pressure measurements. Ambient temperature had a negative linear effect on all 3 home blood pressure parameters after adjusting for demographic and clinical factors and antihypertensive agents. A 1°C decrease was associated with a 0.5492-mm Hg increase in mean blood pressure, a 0.6841-mm Hg increase in systolic blood pressure, and a 0.2709-mm Hg increase in diastolic blood pressure. This temperature effect on home blood pressure was less prominent in patients with diabetes or hypertension. Antihypertensive agents modified this negative effect of temperature on home blood pressure to some extent, and angiotensin receptor blockers had the most favorable results.

CONCLUSIONS

Short-term exposure to low ambient temperature significantly increased home blood pressure in patients with chronic cardiovascular diseases. Antihypertensive agents may modify this effect.

Effects of lifestyle advice provided by pharmacists on blood pressure: The COMmunity Pharmacists ASSist for Blood Pressure (COMPASS-BP) randomized trial

The COMmunity Pharamcists ASSist for Blood Pressure (COMPASS-BP) study aimed to assess the effectiveness of lifestyle support programs administered in community pharmacies on hypertension control. This open-label, two-armed parallel group, cluster-randomized controlled trial included 73 pharmacies (clusters) in Japan randomized to a control or intervention group. Eligible hypertensive patients (n = 125), aged 20-75 years, received the intervention (n = 64) or the control treatment (n = 61), as dictated by their pharmacy randomization. Patients in the intervention group received brochures and healthy lifestyle advice from pharmacists using motivational interviewing methods during pharmacy visits over a 12-week period, with their usual pharmacy care. Conversely, the control group just received usual care. The main outcome measure was a change in morning systolic blood pressure (SBP) from baseline to week 12. The intervention group exhibited a decrease in morning SBP that was 6.0 mmHg greater than that of the control group (95% confidence interval [CI]: -11.0 to -0.9, p = 0.021). In a mixed-effect model for repeated measures analysis, the intergroup difference in morning SBP decrease was -4.5 mmHg (95% CI: -8.5 to -0.6, p = 0.024). Our findings indicate that implementation of a lifestyle advice program in pharmacies is feasible and may lead to reduced blood pressure.

Onset seasons and clinical outcomes in patients with Stanford type A acute aortic dissection: an observational retrospective study

OBJECTIVES

To evaluate the association of onset season with clinical outcome in type A acute aortic dissection (AAD).

DESIGN

A single-centre, observational retrospective study.

SETTING

The study was conducted in Fuwai Hospital, the National Centre for Cardiovascular Disease, Beijing, China.

PARTICIPANTS

From 2008 to 2010, a set of consecutive patients with type A AAD, confirmed by CT scanning, were enrolled and divided into four groups according to onset season: winter (December, January and February), spring (March, April and May), summer (June, July and August) and autumn (September, October and November). The primary end points were in-hospital death and all-cause mortality during follow-up.

RESULTS

Of the 492 cases in this study, 129 occurred in winter (26.2%), 147 in spring (29.9%), 92 in summer (18.7%), and 124 in autumn (25.2%). After a median follow-up of 20.4 months (IQR 9.7-38.9), the in-hospital mortality in cases occurring in autumn was higher than in the other three seasons (23.4% vs 8.4%, p<0.01). Long-term mortality was comparable among the four seasonal groups (p=0.63). After adjustment for age, gender and other risk factors, onset in autumn was still an independent factor associated with increased risk of in-hospital mortality (HR 2.05; 95% CI 1.15 to 3.64, p=0.02) in addition to surgical treatment. Further analysis showed that the seasonal effect on in-hospital mortality (autumn vs other seasons: 57.4% vs 27.3%, p<0.01) was only significant in patients who did not receive surgical treatment. No seasonal effect on long-term clinical outcomes was found in this cohort.

CONCLUSIONS

Onset in autumn may be a factor that increases the risk of in-hospital death from type A AAD, especially in patients who receive conservative treatment. Immediate surgery improves the short-term and long-term outcomes regardless of onset season.

Seasonal Variation in Blood Pressure in 162,135 Patients With Type 1 or Type 2 Diabetes Mellitus

Seasonal variation in blood pressure (BP) has been observed in different populations. However, only few studies have focused on BP seasonality in diabetic patients. This study examined the seasonal patterns in BP in 62,589 patients with type 1 diabetes mellitus (T1DM) and in 99,546 patients with type 2 diabetes mellitus (T2DM) from the German/Austrian Diabetes Follow-up Registry. Adjusted mean BP values revealed seasonal cycles of 12 months, with higher BP in colder months. Using harmonic regression models, the estimated systolic BP difference throughout the year was 2.28/2.48 mm Hg in T1DM/T2DM (both P<.001). Interestingly, seasonal variation in diastolic BP was larger in T1DM than in T2DM (1.24/0.64 mm Hg, P<.001). A sex difference was observed in T1DM only, while age differences occurred in both types of diabetes. Correlations between BP and potentially related factors such as outdoor temperature indicated that reasons underlying BP seasonality are likely to be complex and vary by subgroup.

Does local ambient temperature impact children's blood pressure? A Chinese National Survey

BACKGROUND

Several studies demonstrated a short-term association between ambient temperature and blood pressure. However, few studies have assessed the long-term effect of ambient temperature on children's blood pressure. The present study aimed to investigate the association between long-term exposure to local ambient temperature and children's blood pressure in China.

METHODS

We analyzed the systolic (SBP) and diastolic blood pressure (DBP) data of 71,763 children from 2010 Chinese National Survey on Students' Construction and Health (CHNSCH), and local annual average ambient temperature, relative humidity, air pollutants data from China Meteorological Administration and Ministry of Environment Protection of China. We used generalized additive model (GAM) with non-linear function to examine the effects of ambient temperature on children's blood pressure.

RESULTS

The results showed that decrease of ambient temperature was negatively associated with increase of both SBP and DBP in Chinese children while adjusting for individual characteristics, socioeconomic conditions, air pollutants and relative humidity. The largest alteration of SBP related to the temperature difference was observed from 20.4 to 9.6 °C, with 9.0 mmHg (95 % CI: 8.4, 9.5) increase in SBP, while the largest alteration of DBP was observed from 21.7 to 10.2 °C, with 6.1 mmHg (95 % CI: 5.6, 6.6) increase in DBP. However, when temperature below 9.6 and 10.2 °C, SBP and DBP started to decrease, which might be caused by the use of heating system in the extreme cold areas.

CONCLUSIONS

Public health policy should be improved for protecting children's cardiovascular health from adverse effects of low temperature. Development of heating system in moderate cold area might be a good solution.

Outdoor Temperature, Heart Rate and Blood Pressure in Chinese Adults: Effect Modification by Individual Characteristics

We collected data from Kailuan cohort study from 2006 to 2011 to examine whether short-term effects of ambient temperature on heart rate (HR) and blood pressure (BP) are non-linear or linear, and their potential modifying factors. The HR, BP and individual information, including basic characteristics, life style, socio-economic characteristics and other characteristics, were collected for each participant. Daily mean temperature and relative humidity were collected. A regression model was used to evaluate associations of temperature with HR and BP, with a non-linear function for temperature. We also stratified the analyses in different groups divided by individual characteristics. 47,591 residents were recruited. The relationships of temperature with HR and BP were “V” shaped with thresholds ranging from 22 °C to 28 °C. Both cold and hot effects were observed on HR and BP. The differences of effect estimates were observed among the strata of individual characteristics. The effect estimate of temperature was higher among older people. The cold effect estimate was higher among people with lower Body Mass Index. However, the differences of effect estimates among other groups were inconsistent. These findings suggest both cold and hot temperatures may have short-term impacts on HR and BP. The individual characteristics could modify these relationships.

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

Higher level of blood pressure (BP) in winter than in summer has been observed, but the association between temperature and BP and its potential modifiers with adjustment of individual confounders and time trends was rarely explored. We aimed to investigate the association between outdoor temperature and BP and its potential modification factors in a longitudinal panel study in Shanghai, China. From January 2011 to December 2012, we scheduled 54 follow-ups for BP measurements per subject via home visit every other week for 50 elderly hypertensive patients. We applied linear mixed-effect models to analyze the association between temperature and BP after controlling for individual characteristics, antihypertensive medication, comorbidities, and time trends. We evaluated the potential effect modifiers by stratification analyses. For a 1 °C decrease in the average temperature on concurrent day and previous day, systolic BP increased by 0.19 mmHg (95 % confidence interval = 0.06, 0.31) and diastolic BP increased by 0.12 mmHg (95 % confidence interval = 0.03, 0.21). The effect of temperature on BP was stronger among those with older age, female sex, low socioeconomic status, and obese physique. The effect was weak and even null for those taking the angiotensin receptor blockers, angiotensin-converting enzyme inhibitor, or its combination with calcium antagonists. Further, the effect was almost restricted within those having chronic comorbidities. Our results demonstrated that an acute decrease in outdoor temperature was significantly associated with a rise in BP among elderly hypertensive patients, in Shanghai, China. Individual characteristics, antihypertensive medications, and comorbidities may modify this effect.

Analysis of association between brain natriuretic peptide levels and blood pressure variability

The present study aimed to investigate the association between plasma brain natriuretic peptide (BNP) levels and systolic blood pressure (SBP) variability over a one-year period. Blood pressure was measured in 44 patients treated for hypertension (73±9 years old) at an outpatient clinic every one to two months over a one-year period. The standard deviation (SD) and the coefficient of variation (CV) were calculated to assess SBP variability. Mean SBP was also calculated over the year. Plasma BNP levels were measured at the end of the one-year period. BNP was found to correlate with mean SBP (r=0.599; P<0.001). However, BNP was not observed to be correlate with either the SD (r=0.219; P=0.153) or the CV (r=0.058; P=0.709) of the SBP. Multiple regression analysis revealed that only the mean values of SBP were independently associated with BNP (β=0.613; P<0.001). Thus, BNP was found to be correlated with mean SBP, but not SBP variability. In conclusion, plasma BNP levels may reflect the average SBP, but not SBP variability over the one-year period prior to the measurement of BNP in patients with hypertension.

Winter Hypertension: Potential mechanisms

Hypertension exhibits a winter peak and summer trough in countries both north and south of the equator. A variety of explanations have been proposed to account for the seasonal nature of hypertension. It is likely that this reflects seasonal variations in risk factors. Seasonal variations have been demonstrated in a number of risk factors may play essential roles for seasonality of hypertension such as noradrenalin, catecholamine and vasopressin, vitamin D, and serum cholesterol. However, a number of studies have also suggested a direct effect of environmental temperature and physical activity on blood pressure. This paper was design to review the available evidence on seasonal variations in hypertension and possible explanations for them.

Blood pressure response to patterns of weather fluctuations and effect on mortality

Very few studies have looked at longitudinal intraindividual blood pressure responses to weather conditions. There are no data to suggest that specific response to changes in weather will have an impact on survival. We analyzed >169 000 clinic visits of 16 010 Glasgow Blood Pressure Clinic patients with hypertension. Each clinic visit was mapped to the mean West of Scotland monthly weather (temperature, sunshine, rainfall) data. Percentage change in blood pressure was calculated between pairs of consecutive clinic visits, where the weather alternated between 2 extreme quartiles (Q(1)-Q(4) or Q(4)-Q(1)) or remained in the same quartile (Q(n)-Q(n)) of each weather parameter. Subjects were also categorized into 2 groups depending on whether their blood pressure response in Q(1)-Q(4) or Q(4)-Q(1) were concordant or discordant to Q(n)-Q(n). Generalized estimating equations and Cox proportional hazards model were used to model the effect on longitudinal blood pressure and mortality, respectively. Q(n)-Q(n) showed a mean 2% drop in blood pressure consistently, whereas Q(4)-Q(1) showed a mean 2.1% and 1.6% rise in systolic and diastolic blood pressure, respectively. However, Q(1)-Q(4) did not show significant changes in blood pressure. Temperature-sensitive subjects had significantly higher mortality (1.35 [95% confidence interval, 1.06-1.71]; P=0.01) and higher follow-up systolic blood pressure (1.85 [95% confidence interval, 0.24-3.46]; P=0.02) compared with temperature-nonsensitive subjects. Blood pressure response to temperature may be one of the underlying mechanisms that determine long-term blood pressure variability. Knowing a patient's blood pressure response to weather can help reduce unnecessary antihypertensive treatment modification, which may in turn increase blood pressure variability and, thus, risk.

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.

Vitamin D status partly explains ethnic differences in blood pressure: the 'Surinamese in the Netherlands: study on ethnicity and health'

OBJECTIVE

To investigate the role of vitamin D in explaining ethnic differences in blood pressure among three ethnic groups in the Netherlands (ethnic Dutch, African Surinamese, and south Asian Surinamese).

METHODS

Data were derived from the 'Surinamese in the Netherlands: study on ethnicity and health' study, a population-based observational study. We included 1420 participants (505 ethnic Dutch, 330 south Asian Surinamese, and 585 African Surinamese), aged 35-60 years, in whom serum vitamin D (25-hydroxyvitamin D) and SBP and DBP were measured. Data were analyzed by using linear (SBP, DBP) and logistic (hypertension) regression analyses, using ethnicity as independent variable and adjusting for potential confounders. To study the impact of vitamin D, we additionally adjusted for vitamin D in a final model.

RESULTS

South Asian Surinamese had a 5.6 mmHg higher SBP and 4.9 mmHg higher DBP as compared with the Dutch after adjustment for age, sex, season, physical activity, smoking, education, and BMI. Further adjustment for vitamin D explained 14 and 6% of these SBP and DBP differences, respectively. African Surinamese had an 8.9 mmHg higher SBP and 6.8 mmHg higher DBP as compared with the Dutch. Variation in vitamin D explained 7 and 4% of these SBP and DBP differences. South Asian Surinamese and African Surinamese had 2.2 (1.5-3.2) and 3.3 (2.4-4.6) times higher odds of having hypertension compared with ethnic Dutch. Vitamin D explained 25 and 17% of the variations in SBP and DBP, respectively, resulting in odds ratio of 1.9 (1.3-2.9) and 2.9 (2.0-4.3), respectively.

CONCLUSION

Higher blood pressures and higher hypertension risk in south Asian Surinamese and African Surinamese were partly explained by their poorer vitamin D status. However, even after adjustment, significant ethnic blood pressure differences persisted.

The skin function: a factor of anti-metabolic syndrome

The body's total antioxidant capacity represents a sum of the antioxidant capacity of various tissues/organs. A decrease in the body's antioxidant capacity may induce oxidative stress and subsequent metabolic syndrome, a clustering of risk factors for type 2 diabetes and cardiovascular disease. The skin, the largest organ of the body, is one of the major components of the body's total antioxidant defense system, primarily through its xenobiotic/drug biotransformation system, reactive oxygen species-scavenging system, and sweat glands- and sebaceous glands-mediated excretion system. Notably, unlike other contributors, the skin contribution is variable, depending on lifestyles and ambient temperature or seasonal variations. Emerging evidence suggests that decreased skin's antioxidant and excretory functions (e.g., due to sedentary lifestyles and low ambient temperature) may increase the risk for metabolic syndrome. This review focuses on the relationship between the variability of skin-mediated detoxification and elimination of exogenous and endogenous toxic substances and the development of metabolic syndrome. The potential role of sebum secretion in lipid and cholesterol homeostasis and its impact on metabolic syndrome, and the association between skin disorders (acanthosis nigricans, acne, and burn) and metabolic syndrome are also discussed.

Effects of weather variability and air pollutants on emergency admissions for cardiovascular and cerebrovascular diseases

We examined the effect of ambient temperature, air pressure and air pollutants on daily emergency admissions by identifying the cause of admission for each type of stroke and cardiovascular disease using generalized linear Poisson regression models allowing for overdispersion, and controlling for seasonal and inter-annual variations, days of the week and public holidays, levels of influenza and respiratory syncytial viruses. Every 1°C decrease in mean temperature was associated with an increase in the daily number of emergency admissions by 7.83% (95% CI 2.06-13.25) for acute coronary syndrome (ACS) and heart failure, by 35.57% (95% CI 15.59-59.02) for intracerebral haemorrhage (ICH) and by 11.71% (95% CI 4.1-19.89) for cerebral infarction. An increase of emergency admissions due to ICH (3.25% (95% CI 0.94-5.51)), heart failure (3.56% (95% CI 1.09-5.96)) was observed at every 1 hPa decrease in air pressure from the previous days. We found stronger detrimental effect of cold on stroke than cardiovascular disease.

Visit-to-visit variability in blood pressure over a 1-year period is a marker of left ventricular diastolic dysfunction in treated hypertensive patients

Although visit-to-visit variability in systolic blood pressure (SBP) has recently been demonstrated to be a strong predictor of stroke, there are no data about relationships between SBP variability and cardiac damage in hypertensive patients. We compared relationships between visit-to-visit variability in SBP and left ventricular (LV) diastolic dysfunction with the relationships between the mean SBP value and cardiac parameters in treated patients. Forty treated hypertensive patients (69 ± 9 years of age) had their blood pressure measured at outpatient clinics every 1 or 2 months over a 1-year period. The standard deviation (s.d.) of SBP and the difference between the maximum and minimum SBPs during this year were calculated to assess visit-to-visit variability. The mean SBP during the year was also calculated. LV diastolic function was assessed by the ratio (E/A) of early (E) and late (A) diastolic transmitral flows, early diastolic mitral annular velocity (e') and the ratio (E/e') of E to e' using Doppler echocardiography. E/A only correlated with the s.d. of SBP (r=-0.327, P=0.040), whereas e' correlated with s.d. of SBP (r=-0.496, P=0.001) and maximum-minimum SBP difference (r=-0.490, P=0.001). E/e' correlated with s.d. of SBP (r=0.384, P=0.014), maximum-minimum SBP difference (r=0.410, P=0.009), and the mean value of SBP (r=0.349, P=0.028). Multiple regression analysis demonstrated only the maximum-minimum SBP difference independently associated with E/e' (β=0.410, P=0.009). Thus, the visit-to-visit variability of SBP showed better correlation with LV diastolic dysfunction than mean values of SBP. High visit-to-visit variability of SBP was associated with LV diastolic dysfunction and may constitute a high risk for diastolic heart failure in hypertensive patients.