Seasonal variations in home and ambulatory blood pressure in the PAMELA population. Pressione Arteriose Monitorate E Loro Associazioni

Seasonal variation in prostate-specific antigen levels: a large cross-sectional study of men in the UK

OBJECTIVE

• To assess whether a seasonal change in prostate specific antigen (PSA) levels can be detected in men recruited to a large clinical trial.

PATIENTS AND METHODS

• A total of 66 969 men aged 50-69 years were drawn from a large study conducted at general practices across the UK between 2002 and 2007. • Trigonometric algorithms and regression methods were used to assess the relationship between the time of year and serum PSA and blood pressure measurements. • We obtained local daily mean temperatures and hours of sunlight per day to assess whether these factors were potential mechanisms for seasonal variation in PSA levels or blood pressure. • The proportion of participants who would be considered clinically at risk according to their PSA or blood pressure measurement, by month, was also assessed. • The strength of associations between time of year and blood pressure were used to reinforce conclusions from the PSA models.

RESULTS

• There was no relationship between time of year and PSA levels (P= 0.11) or between climate and PSA levels (P= 0.42). • No difference was found in the prevalence of clinically raised PSA content by month (P= 0.50). • This lack of an association with PSA content was despite our data being sufficient to provide clear evidence of an association between blood pressure and time of year (systolic P < 0.001; diastolic P < 0.001), and to show that this association was largely explained by climatic factors (temperature and sunlight).

CONCLUSION

• There was no pattern in PSA levels by time of year, air temperature or levels of sunlight in this cohort, so there is no need to take these factors into account when reviewing PSA results.

Seasonal variation in home blood pressure measurements and relation to outside temperature in Japan

Previous studies have suggested that outside temperature affects blood pressure (BP) levels. However, recently, due to a spreading heating system, the seasonal variation in BP levels might be smaller, especially in colder seasons when more heat is used. We used continuous measurements of home BP data to track seasonal variations of BP to analyze the relation between outside temperature and BP values. Among 213 volunteers who were asked to measure BP in September 2000, 79 participants (mean age 72.7 years, 60.0% women) measured BP at least once per month until August 2003 (36 months). The mean number of measurements was 19.0 times/month. Information on outside temperature was provided by the Japan Meteorological Agency. We used general linear models to analyze the relation between outside temperature and BP values. Blood pressure levels were lowest in the warmest months. However, the highest BP levels were not observed in the coldest month, but rather in March. A clear inverse association between temperature and BP values was evident only in periods when outside temperatures were above 10°C. When the outside temperature was ≥ 10°C, 1°C increment of outside temperature correspond to 0.40 and 0.28 mmHg decrease of systolic blood pressure (SBP) and diastolic blood pressure (DBP), whereas the corresponding values were 0.06 and 0.01 mmHg when the outside temperature was <10°C. In conclusion, inverse association between outside temperature and BP was observed only in warmer seasons.

The association of remotely-sensed outdoor temperature with blood pressure levels in REGARDS: a cross-sectional study of a large, national cohort of African-American and white participants

BACKGROUND

Evidence is mounting regarding the clinically significant effect of temperature on blood pressure.

METHODS

In this cross-sectional study the authors obtained minimum and maximum temperatures and their respective previous week variances at the geographic locations of the self-reported residences of 26,018 participants from a national cohort of blacks and whites, aged 45+. Linear regression of data from 20,623 participants was used in final multivariable models to determine if these temperature measures were associated with levels of systolic or diastolic blood pressure, and whether these relations were modified by stroke-risk region, race, education, income, sex hypertensive medication status, or age.

RESULTS

After adjustment for confounders, same-day maximum temperatures 20 °F lower had significant associations with 1.4 mmHg (95% CI: 1.0, 1.9) higher systolic and 0.5 mmHg (95% CI: 0.3, 0.8) higher diastolic blood pressures. Same-day minimum temperatures 20 °F lower had a significant association with 0.7 mmHg (95% CI: 0.3, 1.0) higher systolic blood pressures but no significant association with diastolic blood pressure differences. Maximum and minimum previous-week temperature variabilities showed significant but weak relationships with blood pressures. Parameter estimates showed effect modification of negligible magnitude.

CONCLUSIONS

This study found significant associations between outdoor temperature and blood pressure levels, which remained after adjustment for various confounders including season. This relationship showed negligible effect modification.

High Water Evaporation Rate is Associated with Low Blood Pressure in Chronic Peritoneal Dialysis Patients

Background

The relationship between water evaporation rate (WER) and blood pressure (BP) in continuous ambulatory peritoneal dialysis (CAPD) patients has not been addressed before. This study was undertaken to evaluate the effects of WER on the BP and body weight (BW) of end-stage renal disease patients treated with CAPD.

Methods

Based on mean WER of each month, the year 2005 was divided into “high WER” and “low WER” stages. This study enrolled 66 CAPD patients at our center during 2005. The BP and BW of each patient were collected monthly. WER was measured with a class A evaporation pan.

Results

Compared to the high WER stage, CAPD patients had higher BP (systolic: 142 ± 29 vs 134 ± 27 mmHg, p < 0.001; diastolic: 86 ± 17 vs 84 ± 16 mmHg, p < 0.001) and BW (56.8 ± 10.2 vs 56.1 ± 10.2 kg, p < 0.001) in the low WER stage. Ambient temperature was significantly higher in the high WER stage ( p = 0.004) and it was also positively correlated with WER ( r = 0.82, p = 0.0012). Both mean BP ( r = –0.72, p = 0.0089) and BW ( r = –0.79, p = 0.002) showed inverse relationships to the WER. Moreover, both mean BP ( r = –0.95, p < 0.001) and BW ( r = –0.90, p < 0.001) also showed negative linear regressions to ambient temperature. There was a positive linear regression between mean BP and BW ( r = 0.85, p = 0.0004). Multiple linear regression analysis found that WER (β = –0.672, p = 0.026) was an independent factor correlated to patients’ mean BP.

Conclusions

CAPD patients had lower BP and BW in the high WER stage. These decreases were associated with higher ambient temperature and WER. We hypothesize that increased insensible salt and fluid loss secondary to high WER during hot seasons, especially in subtropical areas, ameliorates the hypervolemia and hypertension in CAPD patients.

Inverse correlation between seasonal changes in home blood pressure and atmospheric temperature in treated-hypertensive patients

We examined the relationships between home blood pressure (BP) and atmospheric temperature in 20 treated-hypertensive patients. A significant correlation between morning and evening BP and atmospheric temperature was found. For morning systolic blood pressure (SBP), the maximal seasonal difference was 13.2 mmHg with 25.5 degrees C temperature difference. Morning SBP increased by approximately 0.41 mmHg with a 1 degrees C decrease in atmospheric temperature. A similar but weaker correlation with temperature was observed for morning diastolic, evening systolic and diastolic blood pressure (DBP). The present study provides important information in respect to BP changes with atmospheric temperature that should be taken into account in the analysis and treatment of hypertension.

Impact of outdoor temperature on prewaking morning surge and nocturnal decline in blood pressure in a Japanese population

Seasonal variations in blood pressure (BP) have often been attributed to meteorological factors, especially changes in outdoor temperature. We evaluated the direct association between meteorological factors and circadian BP variability. Twenty-four-hour ambulatory BP was monitored continuously for 7 days in 158 subjects. Mean awake, asleep, morning (first 2 h after waking) BP, prewaking morning BP surge (morning systolic BP (SBP)-mean SBP during the 2-h period before waking) and nocturnal BP decline were measured each day. We compared BP values for the lowest and highest days with regard to the daily mean outdoor temperature and mean atmospheric pressure. Morning BP and prewaking morning BP surge on the coldest day were significantly higher than those on the warmest day (morning SBP, 136.6 ± 1.6 vs. 133.1 ± 1.5 mm Hg, P = 0.002; morning diastolic BP, 84.4 ± 0.9 vs. 82.6 ± 0.9 mm Hg, P = 0.02; and prewaking morning BP surge, 20.8 ± 1.3 vs. 15.3 ± 1.3 mm Hg, P = 0.0004). The magnitude of nocturnal BP decline on the coldest day was significantly greater than that on the warmest day (15.8 ± 0.7 vs. 13.9 ± 0.7%, P = 0.01). Outdoor temperature is an important determinant of morning BP, prewaking morning BP surge and the magnitude of nocturnal BP decline. These findings may have important implications in management of hypertension and prevention of cardiovascular events.

Seasonal variation in haemodynamics and blood pressure-regulating hormones

Seasonal variation in blood pressure (BP) has been described in some people, although the variation is small for both systolic and diastolic BPs. The aim of this study was to elucidate underlying haemodynamic and hormonal mechanisms that may occur to defend seasonal changes in BP. Participants were 27 men and 7 women with either normal BP or early hypertension. Measurements of haemodynamics (cardiac output by dual-gas rebreathing) and hormones (resting catecholamines, renin activity, and aldosterone by radioenzymatic assay or radioimmunoassay) were performed during the summer, fall, winter, and spring seasons. Student's paired t-test with Bonferroni modification and regression analyses were used to examine the data with a significance level of P<0.05. Systolic and diastolic BP remained relatively constant across seasons. Cardiac output and stroke volume significantly decreased 10 and 15%, respectively, from summer to winter, whereas heart rate and systemic vascular resistance significantly increased 5 and 11%, respectively. Plasma aldosterone (PA) significantly increased 59% from summer to winter, whereas plasma norepinephrine (PNE), plasma epinephrine, and plasma renin activity (PRA) increased 19, 2, and 17%, respectively (pNS for each). Across the four seasons, mean arterial pressure significantly correlated with PRA and PA, whereas systemic vascular resistance significantly correlated with PNE and PRA. There are dramatic counterregulatory haemodynamic and hormonal adaptations to maintain a relatively constant BP. Norepinephrine, PRA, and aldosterone have a function in mediating the changes in haemodynamics.

[Medical consequences of global warming]

INTRODUCTION

The global warming of the planet and its anthropogenic origin are no longer debatable. Nevertheless, from a medical point of view, while the epidemiological consequences of the warming are rather well-known, the biological consequences are still poorly documented. This is a good example of evolutionary (or darwinian) medicine.

METHODS

The research strategy of this systematic review is based on both PubMed during the period of 2000-2007 and several reviews articles for the period >2000.

RESULTS

From a medical point of view, there are four types of consequences. 1-The simple elevation of the average external temperature is accompanied by an increased global mortality and morbidity, the mortality/external temperature is a J curve, with the warm branch more pronounced than the cold one. A recent study on 50 different cities had confirmed that global, and more specifically cardiovascular mortalities were enhanced at the two extreme of the temperatures. 2-The acute heatwaves, such as that which happened in France in August 2003, have been studied in detail by several groups. The mortality which was observed during the recent heatwaves was not compensated by harvesting, strongly suggesting that we were dealing with heat stroke, and that such an increased mortality was more reflecting the limits of our adaptational capacities than aggravation of a previously altered health status. 3-Climate changes have modified the repartition and virulence of pathogenic agents (dengue, malaria...) and above all their vectors. Such modifications were exponential and are likely to reflect the biological properties of parasites. 4-Indirect consequences of global warming include variations in the hydraulic cycle, the new form of tropical hurricanes and many different changes affecting both biodiversity and ecosystems. They will likely result in an increased level of poverty.

DISCUSSION

These finding gave rise to several basic biological questions, rarely evoked, and that concern the limits of the adaptational capacities of human genome. Our genome has indeed been shaped in the past by a rather cold environment which has acutely been modified. The immediate physiological regulation includes sweating and skin vasodilatation. The latter may strongly enhance the cardiac output which explains the heat-induced cardiac decompensation. Long term regulation depends upon the numerous mechanisms of uncoupling of the mitochondrial respiration. For the moment, the thermolytic mechanisms and their regulation were rather poorly documented.

Does B-type natriuretic peptide predict the new onset of hypertension?

Increased B-type natriuretic peptide (BNP) expression precedes the development of hypertension in spontaneously hypertensive rats. We therefore tested the hypothesis that elevated plasma BNP levels predict the onset of hypertension in normotensive subjects. Japanese normotensive participants who were at our hospital for a yearly physical check-up (mean age 52.7 years, 35.9% women, n=5,026) were enrolled in the study. Blood pressure and BNP were measured at baseline and subjects were followed up for 5 years (median 1,114 d), with the endpoint being the development of hypertension. We evaluated the relationship between plasma BNP levels at baseline and the incidence of hypertension during the follow-up period. Hypertension was defined as systolic or diastolic blood pressure > or =140 or > or =90 mmHg, respectively, or the use of antihypertensive medications. During the follow-up period, hypertension developed in 23.4% (77.0 per 1,000 person-years) and 14.9% (51.0 per 1,000 person-years) of male and female subjects, respectively. Cox proportional hazard regression analysis demonstrated that after adjustment for known risk factors, the risk of hypertension was increased from the first to fourth quartiles of baseline BNP levels. However, after additional adjustment for baseline blood pressure, BNP did not predict the new onset of hypertension. Baseline BNP levels are closely associated with the risk of hypertension in individuals with normal blood pressure, but the prediction of hypertension with BNP is largely dependent on baseline blood pressure. Measurements of BNP may serve as a complementary method for the prediction or confirmation of hypertension.

A synoptic approach to weather conditions discloses a relationship with ambulatory blood pressure in hypertensives

BACKGROUND

Higher blood pressure (BP) values in cold than in hot months has been documented in hypertensives. These changes may potentially contribute to the observed excess winter cardiovascular mortality. However, the association with weather has always been investigated by considering the relationship with a single variable rather than considering the combination of ground weather variables characterizing a specific weather pattern (air mass (AM)).

METHODS

We retrospectively investigate in Florence (Italy) the relationship between BP and specific AMs in hypertensive subjects (n = 540) referred to our Hypertension Unit for 24-h ambulatory BP monitoring during the period of the year characterized by the highest weather variability (winter). Five different winter daily AMs were classified according to the combination of ground weather data (air temperature, cloud cover, relative humidity, atmospheric pressure, wind speed, and direction).

RESULTS

Multiple variable analysis selected the AM as a significant predictor of mean 24-h BP (P < 0.01 for diastolic BP (DBP) and P < 0.05 for systolic BP (SBP)), daytime DBP (P < 0.001) and nighttime BP (P < 0.01 for both SBP and DBP), with higher BP values observed in cyclonic (unstable, cloudy, and mild weather) than in anticyclonic (settled, cloudless, and cold weather) days. When the association with 2-day sequences of AMs was considered, an increase in ambulatory BP followed a sudden day-to-day change of weather pattern going from anticyclonic to cyclonic days.

CONCLUSIONS

The weather considered as a combination of different weather variables may affect BP. The forecast of a sudden change of AM could provide important information helpful for hypertensives during winter.

The effect of temperature on systolic blood pressure

OBJECTIVES

To quantify the association between systolic blood pressure and season, indoor and outdoor temperature and short-term trends in outdoor temperature.

METHODS

The study used data from the WHO MONICA Project risk factors surveys from 25 populations in 16 countries. Random samples of men and women aged 35-64 years were invited to participate. Systolic blood pressure measurements were available for 115 434 participants. Hierarchical models were used to quantify the association between blood pressure and temperature, and account for differences in the associations between populations.

RESULTS

Populations closer to the equator showed larger seasonal changes in blood pressure. A 1 degrees C increase in indoor temperature reduced systolic blood pressure by an average of 0.31 mmHg (95% posterior interval: -0.44, -0.19). A 1 degrees C increase in outdoor temperature reduced blood pressure by the smaller average of 0.19 mmHg (95% posterior interval: -0.26, -0.11). Increased outdoor, but not indoor, temperatures had a stronger effect in women than in men. The effect of outdoor temperature remained after controlling for indoor temperature. Short-term trends in temperature did not have a statistically signicant effect.

CONCLUSIONS

Indoor and outdoor temperature have independent effects on systolic blood pressure, and both should be controlled for in studies that measure blood pressure. Improved protection against cold temperatures could lead to a reduction in the winter excess of cardiovascular mortality.

Seasonal Variations in Blood Pressure

The influence of temperature changes on risk factors like hypertension is often disregarded despite extensive literature on the phenomenon. Numerous surveys and studies have documented the correlation between temperature and blood pressure in various countries among adults, the elderly, and children. Twenty-four-hour blood pressure studies also generally show higher blood pressure in the winter. The suggested etiology is that cold increases sympathetic tone, evidenced by elevated blood pressure and plasma and urinary noradrenaline concentrations. The lower blood pressure in warm temperatures is attributed to cutaneous vasodilatation and loss of water and salt from sweating. Taking seasonal variations in blood pressure into account will increase the meaningful information collected in population surveys and mass screenings. It will also result in more personalized management of antihypertensive medications tailored to the individual.

Infradian awake and asleep systolic and diastolic blood pressure rhythms in humans

BACKGROUND

Blood pressure shows 24-h rhythms with a significant seasonal fluctuation.

OBJECTIVES

To characterize 2-month to 12-month infradian rhythms in the mean awake and asleep systolic blood pressure (SBP) and diastolic blood pressure (DBP) in humans.

METHODS

A total of 1689 participants underwent 24-h ambulatory blood pressure monitoring during different periods of the year. The mean daily temperature, humidity, barometric pressure and wind velocity values for the same time span and geographical location were obtained. Fourier analysis was used to fit 12-month, 6-month, 4-month, 3-month and 2-month rhythms to the mean awake and asleep SBP and DBP and to metereological variables.

RESULTS

The awake mean SBP and DBP values showed significant 12-month and 3-month rhythms (respectively, R2 = 55%, P < 0.001 and R2 = 45% P < 0.001), with a peak in July (winter) and a trough-peak difference of 6.2 +/- 1.6 mmHg (P < 0.001, SBP) and 4.2 +/- 1.5 mmHg (P < 0.001, DBP). In contrast, asleep blood pressure means showed mainly 3-month rhythms (SBP, R2 = 19%, P < 0.02; DBP, R2 = 43% P < 0.02). Mean daily temperature and humidity showed at 12-month, 6-month, 4-month, 3-month and 2-month rhythms, barometric pressure showed 12-month and 6-month rhythms, and wind velocity showed 12-month and 3-month rhythms. Minimal temperature values and maximal humidity values coincided with elevated blood pressure values.

CONCLUSION

Awake blood pressure means exhibited mainly circannual fluctuations while asleep blood pressure means showed principally 3-month rhythms. Infradian blood pressure variations correlated with some meteorological variables.

Guiding antihypertensive treatment decisions using ambulatory blood pressure monitoring

Compared with isolated clinic measurements, ambulatory blood pressure monitoring (ABPM) provides an insight into blood pressure (BP) changes in everyday life and an estimate of the overall BP load exerted on the cardiovascular system over 24 hours. Cross-sectional evidence suggests a direct and significant relationship between ambulatory BP and organ damage. There is also longitudinal evidence for a superior predictive value of 24-hour BP in relation to the risk for cardiovascular morbidity and mortality as opposed to clinic BP. The usefulness of ABPM in pharmacologic studies aimed at evaluating the 24-hour antihypertensive efficacy of different drugs and drug combinations is now acknowledged. Among the mathematical indices available to explore 24-hour BP coverage by treatment, the ABPM-derived smoothness index provides a superior measure of the homogeneity of BP control compared with trough:peak ratios. The main applications of clinical practice should be in identifying patients with isolated office hypertension and those who are nonresponders to treatment, in assessing coverage of the 24-hour BP profile in high-risk patients and in diagnosing suspected treatment-related hypotension.

Weather-related changes in 24-hour blood pressure profile: effects of age and implications for hypertension management

A downward titration of antihypertensive drug regimens in summertime is often performed on the basis of seasonal variations of clinic blood pressure (BP). However, little is known about the actual interaction between outdoor air temperature and the effects of antihypertensive treatment on ambulatory BP. The combined effects of aging, treatment, and daily mean temperature on clinic and ambulatory BP were investigated in 6404 subjects referred to our units between October 1999 and December 2003. Office and mean 24-hour systolic BP, as well as morning pressure surge, were significantly lower in hot (>90th percentiles of air temperature; 136+/-19, 130+/-14, and 33.3+/-16.1 mm Hg; P<0.05 for all), and higher in cold (<10th percentiles) days (141+/-12, 133+/-11, and 37.3+/-9.5 mm Hg; at least P<0.05 for all) when compared with intermediate days (138+/-18, 132+/-14, and 35.3+/-15.4 mm Hg). At regression analysis, 24-hour and daytime systolic pressure were inversely related to temperature (P<0.01 for all). Conversely, nighttime systolic pressure was positively related to temperature (P<0.02), with hot days being associated with higher nighttime pressure. Air temperature was identified as an independent predictor of nighttime systolic pressure increase in the group of elderly treated hypertensive subjects only. No significant relationship was found between air temperature and heart rate. Our results show for the first time that hot weather is associated with an increase in systolic pressure at night in treated elderly hypertensive subjects. This may be because of a nocturnal BP escape from the effects of a lighter summertime drug regimen and may have important implications for seasonal modulation of antihypertensive treatment.

Seasonal patterns in monthly hemoglobin A1c values

The purpose of this study was to investigate seasonal variations in population monthly hemoglobin A(1c) (A1c) values over 2 years (from October 1998 to September 2000) among US diabetic veterans. The study cohort included 285,705 veterans with 856,181 A1c tests. The authors calculated the monthly average A1c values for the overall population and for subpopulations defined by age, sex, race, insulin use, and climate regions. A1c values were higher in winter and lower in summer with a difference of 0.22. The proportion of A1c values greater than 9.0% followed a similar seasonal pattern that varied from 17.3% to 25.3%. Seasonal autoregressive models including trigonometric function terms were fit to the monthly average A1c values. There were significant seasonal effects; the seasonal variation was consistent across different subpopulations. Regions with colder winter temperatures had larger winter-summer contrasts than did those with warmer winter temperatures. The seasonal patterns followed trends similar to those of many physiologic markers, cardiovascular and other diabetes outcomes, and mortality. These findings have implications for health-care service research in quality-of-care assessment, epidemiologic studies investigating population trends and risk factors, and clinical trials or program evaluations of treatments or interventions.

[Lack of association between blood pressure variability and left ventricular hypertrophy in essential hypertension]

BACKGROUND AND OBJECTIVE

Blood pressure (BP) fluctuations may contribute to the development of target organ damage in essential hypertension. However, a possible relationship with left ventricular hypertrophy (LVH) is controversial. The aim of the present study was to analyze the association between BP variability, defined through different instrument measures, and LVH in a group of essential hypertensive patients.

PATIENTS AND METHOD

Forty-three untreated hypertensive patients were studied. BP variability was evaluated by using both non-invasive, beat-to-beat finger 24-hour monitoring (Portapres) and discontinuous oscillometric ambulatory blood pressure monitoring (ABPM). All patients underwent echocardiography in order to detect the presence or absence of LVH.

RESULTS

Thirty out of 43 patients studied (70%) exhibited LVH. Office [167.7 (19.5) versus 156.7 (14.9) mmHg; p = 0.032], 24-hour ambulatory [146.6 (15.7) versus 131.9 (15.1) mmHg; p = 0.003] and 24-hour continuous finger [147.5 (21.3) versus 135.7 (14.2) mmHg; p = 0.046] systolic BP were significantly higher in patients with LVH with respect to those without cardiac hypertrophy. No differences were observed in terms of nocturnal BP fall, ABPM 24-h standard deviation of BP or continuous finger BP variability estimates.

CONCLUSION

Left ventricular hypertrophy is mainly correlated with the severity of systolic BP elevation, but not with BP variability, neither long-term nor short-term.

Seasonal modifications in blood pressure are mainly related to interdialytic body weight gain in dialysis patients

BACKGROUND

Longitudinal studies in dialysis patients have identified seasonal variations in blood pressure that may follow climatic parameters such as external temperature and humidity. We aimed to assess the participation of interdialytic body weight gain variations in the seasonal profile of blood pressure.

METHODS

Ninety-nine stable patients (40 F/59 M), 52.9 +/- 1.5 years old, dialyzed in a single satellite dialysis unit between January 7, 1991, and September 30, 1998 were studied. Supine systolic and diastolic blood pressure, body weight, and interdialytic body weight gain were determined at every one of the 38,769 dialyses included, and studied along with climatology data obtained from Météo, France.

RESULTS

Blood pressure varied throughout the year, following a cyclic pattern. It increased from the autumn months toward winter, and decreased toward the spring and warmer months. Systolic and diastolic blood pressures were strongly correlated with interdialytic body weight gain (r= 0.925; P < 0.0001 and r= 0.888; P= 0.0001, respectively). Blood pressure was also correlated with the climatic factors: rainfall (r= 0.786; P < 0.003 and r= 0.784; P < 0.003), humidity (r= 0.701; P= 0.011 and r= 0.699; P < 0.012), and day light span (r=-0712; P < 0.01, and r=-0.658; P < 0.02, respectively). Multivariate regression analyses taking blood pressure as a dependent variable retained interdialytic body weight gain as the first variable in the model.

CONCLUSION

Our results establish a strong link between blood pressure variations and interdialytic body weight gain, showing the important participation of volume state in modulating blood pressure in this group of patients.

Seasonal hypertension: a clue to explain the high prevalence of unrecognized hypertension in the elderly? Gruppo Italiano di Farmacovigilanza nell'Anziano (GIFA)

BACKGROUND AND AIMS

Blood pressure is known to be influenced by the season, particularly in the elderly. The association between cold weather and unrecognized hypertension has not been previously studied. The present study aimed at assessing whether recognition of hypertension in the elderly follows a seasonal pattern.

METHODS

All patients over 64 with either first-listed or secondary diagnosis of hypertension at discharge (N = 4487) out of 24585 consecutively admitted to 69 wards of Geriatrics or Internal Medicine during ten bi-monthly observation periods (May-June and September-October) were enrolled. The main outcome of the study was the prevalence of unrecognized hypertension, defined as no mention of hypertension and/or antihypertensive drugs in clinical histories collected on admission, and a first-listed or secondary discharge diagnosis of hypertension.

RESULTS

We found a total of 928 patients with unrecognized hypertension. Being admitted in the September-October period was independently associated with the outcome unrecognized hypertension (OR 1.25, 95% CI 1.08-1.46), as were smoking addiction (OR 1.57, 95% CI 1.23-2.0) and allocation to a medical ward (OR 1.21, 95% CI 1.04-1.41). Negative correlates of the outcome were multiple pathologies (OR 0.85, 95% CI 0.73-0.99), discharge diagnosis of coronary artery disease (OR 0.77, 95% CI 0.64-0.92) or diabetes mellitus (OR 0.81, 95% CI 0.67-0.97).

CONCLUSIONS

Hypertension in the elderly may at least partly follow a seasonal pattern, and this finding may be relevant for screening and therapeutic decisions.

Arm position and blood pressure: a risk factor for hypertension?

The objective of this study was to re-evaluate the effect of arm position on blood pressure (BP) measurement with auscultatory and oscillometric methods including ambulatory blood pressure monitoring (ABPM). The setting was the hospital outpatient department and the subjects chosen were normotensive and hypertensive. The effect of lowering the arm from heart level on indirect systolic BP (SBP) and diastolic BP (DBP) measurement as well as the importance of supporting the horizontal arm were measured. In the sitting position, lowering the supported horizontal arm to the dependent position increased BP measured by a mercury device from 103+/-10/60+/-7 to 111+/-14/67+/-10 mmHg in normotensive subjects, a mean increase of 8/7 mmHg (P<0.01). In hypertensive subjects, a similar manoeuvre increased BP from 143+/-21/78+/-17 to 166+/-29/88+/-20 mmHg, an increase of 23/10 mmHg (P<0.01). Combined results from normotensive and hypertensive subjects demonstrate a direct and proportional association between BP (SBP and DBP) and the increase produced by arm dependency. Similar changes and associations were noted with oscillometric devices in the clinic situation. However, supporting the horizontal arm did not alter BP. Of particular interest, analysis of 13 hypertensive subjects who underwent ABPM on two occasions, once with the arm in the 'usual' position and once with the arm held horizontally for BP measurement during waking hours, demonstrated changes comparable to the other devices. The mean 12-hour BP was 154+/-19/82+/-10 mmHg during the former period and significantly decreased to 141+/-18/74+/-9 mmHg during the latter period (P<0.01). Regression analysis of the change in SBP and DBP with arm position change again demonstrated a close correlation (r(2)=0.8113 and 0.7273; P<0.001) with the artefact being larger with higher systolic and diastolic pressures. In conclusion, arm movements lead to significant artefacts in BP measurement, which are greater, the higher the systolic or diastolic pressure. These systematic errors occur when using both auscultatory and oscillometric (clinic and ABPM) devices and might lead to an erroneous diagnosis of hypertension and unnecessary medication, particularly in individuals with high normal BP levels. Since clinical interpretations of heart level vary, the horizontal arm position should be the unambiguous standard for all sitting and standing BP auscultatory and oscillometric measurements.

Seasonal variations in clinical and laboratory variables among chronic hemodialysis patients

Seasonal variations in BP among chronic hemodialysis patients have been reported. It was hypothesized that other characteristics of these patients might also vary with the seasons. Twenty-one clinical and laboratory variables were examined for seasonal variations among 1445 patients enrolled in the Hemodialysis Study, sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases. Mixed-effects models were applied to longitudinal changes (up to 45 mo) for individual patients for 19 of the 21 variables, which were measured at least twice each year, to determine the seasonal component of each variable. Seasonal variations in the other two variables, i.e., protein and energy intakes determined from annual dietary records, were assessed in cross-sectional comparisons of intakes of patients entering the study at different time points. Thirteen of the 21 variables examined demonstrated statistically significant (P < 0.01) seasonal components in their longitudinal variations. Predialysis blood urea nitrogen concentrations peaked in March, which coincided approximately with the peak protein catabolic rates, as well as protein and energy intakes (determined by dietary recall). Predialysis systolic and diastolic BP values were highest in winter and lowest in summer, corroborating previous reports. In addition, the lower predialysis BP values in summer were associated with higher outdoor temperatures and less interdialytic fluid gain. The mean predialysis hematocrit values were highest in July, which could not be attributed solely to the estimated changes in plasma volume. Seasonal variations in clinical and laboratory variables occur commonly among chronic hemodialysis patients. The reasons for most of these variations are not apparent and require further investigation. Nonetheless, failure to consider these variations might lead to biases in the interpretation of clinical studies. In addition, awareness of these variations might facilitate the interpretation of laboratory results and the clinical treatment of these patients.

Insufficient duration of action of antihypertensive drugs mediates high blood pressure in the morning in hypertensive population: the Ohasama study

Blood pressure (BP) usually peaks in the morning. The circadian variation of the onset of cardiovascular disease mimics this circadian BP variation. To examine the determinants of the BP difference between the self-recorded BP in the morning (home BP) and daytime average ambulatory BP a cross sectional study was done in the general population of Ohasama, Japan. 1207 subjects > or = 20 years measured both home (more than 14 times) and ambulatory BPs (326 treated for hypertension and 881 untreated subjects), The prevalence of subjects with the systolic BP difference (home BP in the morning - daytime ambulatory BP) of > or = 10 mmHg (high morning BP) was 5.6% in untreated normotensives, 2.9% in untreated hypertensives, and 25.8% in treated hypertensives. This trend was also observed for diastolic pressure. Multiple regression analysis demonstrated that age, male sex, and use of antihypertensive drugs were positively associated and day-night difference of BP was negatively associated with the high morning BP, respectively. These results suggest an insufficient duration of antihypertensive action of widely used antihypertensive drugs in Japan from the 1980s to 1990s. The amplitude of the day-night difference of ambulatory BP in subjects with a high morning BP was lower (non-dipping) than that without high morning BP. The high morning BP is not necessarily accompanied by hypertension but might be mediated, at least in part, by an insufficient duration of action of antihypertensive drugs. The high morning BP accompanies so-called non-dipper pattern of circadian BP variation. An insufficient duration of action of drugs may partly mediate non-dipping in subjects with antihypertensive medication.

Seasonal variation in the incidence of aneurysmal subarachnoid hemorrhage in hospital- and community-based studies

OBJECT

The aim of this study was to examine seasonal variations in the onset of aneurysmal subarachnoid hemorrhage (SAH) in one hospital-based and one community-based patient series.

METHODS

The study population consisted of 941 patients with aneurysmal SAH who were admitted to Shimane Prefectural Central Hospital and 358 patients who were treated in Izumo City, Japan. When investigated as a whole, no significant seasonal variations were found in either population; however, in both series, statistically significant seasonal trends, with a peak in winter and a nadir in summer, were found among patients aged 59 years or younger (p < 0.05 for the hospital-based series and p < 0.005 for the community-based series), but not among those aged 60 years or older, regardless of sex. In the hospital-based series, seasonal variations were most apparent at certain times of day, with significant variations observed between 8:00 a.m. and 10:00 a.m. or 8:00 a.m. and noon (p < 0.001 and p < 0.005, respectively), regardless of patient age, and between 4:00 p.m. and 6:00 p.m. for patients aged 59 years or younger (p < 0.05). Consequently, seasonal variations were significant during daytime hours (between 8:00 a.m. and 8:00 p.m., p < 0.005) but not during the night (between 8:00 p.m. and 8:00 a.m.). Similar tendencies were found in the community-based series. Among patients aged 59 years or younger who had no risk factors for SAH, these seasonal variations were significant in both series. In patients with untreated hypertension, who were current smokers and daily alcohol drinkers, however, no significant patterns were observed in either series, even among younger patients.

CONCLUSIONS

In both hospital- and community-based studies, aneurysmal SAH appears to undergo seasonal variation, with a peak in winter and a nadir in summer. This seasonal pattern may be derived mainly from the occurrence of SAH in the morning, but may also be modified by patient age and SAH risk factors, resulting in the masking of significant seasonal patterns when all patients are considered together.

Seasonal variation in outpatient blood pressure in stable renal transplant recipients

Seasonal variation in blood pressure (BP) has been described in the general and dialysis populations, with higher recordings noted in the winter than in the summer. This difference has been attributed to changes in weight, ambient temperature, and length of daylight. In this study, we sought to determine whether such seasonal differences exist in renal transplant recipients, a group with a high prevalence of hypertension. We reviewed our outpatient population of 652 adult renal transplant recipients and identified primary allograft recipients with graft survival >1 year, stable renal function, on both cyclosporine and prednisone, and who had >1 pair of post-first year "winter" (defined as the months of January and February) plus "summer" (defined as the months of July and August) outpatient BP measurements from the same year. One hundred sixty-three patients met entry criteria, from whom 432 BP pairs were obtained. When the most recent pair from each patient was analyzed (n=163), diastolic and mean BP were found to be higher in winter than summer (by 2.5 and 2.3 mmHg, respectively, P<0.01 for each) by a paired Student t test. In a separate analysis using all BP pairs (n=432), systolic, diastolic, and mean BP were found to be significantly higher in winter (by 5.3, 2.7, and 3.5 mmHg, respectively, P<0.001 for each). An effect of season was confirmed in a multiple regression model of common predictors for hypertension, controlling for number of BP pairs per patient. In conclusion, renal transplant recipients demonstrate higher BP in the winter than in the summer. This effect is independent of known predictors of hypertension in this population and may be, at least, partly related to changes in length of daylight and temperature.

Mechanisms and clinical implications of blood pressure variability

Several studies have unequivocally shown that the target-organ damage associated with the hypertensive condition is more closely related to 24 h average blood pressure values than to clinic blood pressure. Blood pressure, however, is highly variable over the daytime and night-time period, and of major interest is whether average 24 h blood pressure values, as well as 24 h blood pressure variability, correlate with, and are possibly responsible for, the hypertension-related alterations of the target-organ structure and function. This paper will address this issue by discussing the main features of blood pressure variability in hypertension. It will also examine the mechanisms involved in this phenomenon, with particular emphasis on the pathogenetic role of sympathetic neural factors. The clinical relevance of blood pressure variability in promoting target-organ damage, as well as its therapeutic implications, will finally be highlighted.

Seasonal variations of blood pressure and overhydration in patients on chronic hemodialysis

Blood pressure (BP) has a seasonal cycle in the general population and in patients undergoing maintenance dialysis, but the causes remain unclear. We studied the BP measurements recorded at fixed hours three times weekly from 1994 to 1997 in 102 hemodialysis patients. We obtained monthly averages of the following variables: predialysis mean BP, greatest overhydration (OH) estimated by predialysis body weight excess over dry weight, chronic OH estimated by the remaining postdialysis weight excess over dry weight, urea reduction ratio (URR) in dialysis, and monthly means for daylight span and outdoor temperature over the study period. Average BP in the population diminished over the 48-month period, associated with a decrease in chronic OH (r = 0.66; P < 0.0005) but independent of greatest OH. BP and chronic OH presented synchronous seasonal variations, with peaks in late autumn and early winter and troughs in summer. These biological rhythms were inversely related to the seasonal daylight span and outdoor temperature. Both BP and chronic OH periods were synchronous with the daylight annual cycle and preceded the seasonal variations of temperature by 1 month. Multiple regression analysis showed that chronic OH and daylight, but not URR or temperature, had a significant independent association with BP changes. These results show the existence of seasonal variations of BP in dialysis patients that are associated and synchronous with seasonal changes in chronic OH status. Both cycles depend on conditions influenced by the annual daylight span more than by external temperature.