Seasonal Variation In Blood Pressure Research Articles

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.

Seasonal Changes in Blood Pressure and Frequency of Related Complications in Elderly Israeli Patients with Essential Hypertension

Background: Earlier studies on hypertension demonstrated seasonal variations in different age groups. However, slightly greater fluctuations were found in the hypertensive elderly. Objective: We conducted a prospective 5-year study from January 1997 to December 2001 to evaluate the seasonal variation in blood pressure and the variables of age, gender, body mass index and related complications in elderly Israeli patients with essential hypertension. Methods: Blood pressure was measured in four seasons in 182 patients (98 men and 84 women; age range 65–91 years) treated for hypertension in our outpatient clinic. Results: Both systolic and diastolic mean blood pressures were higher during winter compared to summer (165 ± 11.6 and 90 ± 13.7 and 134 ± 47.3 and 74 ± 8.5 mm Hg, respectively; p < 0.001). There were no significant seasonal differences between spring and autumn or any correlation between the seasonal winter-summer difference in blood pressure and other studied parameters. Patients aged 65–75 years were unexpectedly more sensitive to winter-summer changes than older patients. There was a correlation between a large winter-summer difference in systolic blood pressure and a body mass index between 20 and 30, but there was none in lower or higher ranges. Supplementary antihypertension treatment was required during winter in 38% of these selected patients. Complications such as myocardial infarctions and strokes occurred twice as frequently in winter than in any other season (p < 0.0001). Conclusions: Both systolic and diastolic blood pressures were highest during winter. Hypertension complications were more frequent in winter. Our results refute those of earlier studies that failed to find significant seasonal variations in blood pressure among the elderly.

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

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. 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. 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. 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.

1009-195 The effect of seasonal variation of blood pressure when analyzing improvement and treating large groups of hypertensive patients

1009-195 The effect of seasonal variation of blood pressure when analyzing improvement and treating large groups of hypertensive patients

Seasonal variations of blood pressure in hemodialysis and renal transplant recipients

Seasonal variations influence blood pressure (BP) in healthy persons. Its effects on BP in renal replacement therapy, especially after renal transplantation (RTX), have not been proven clearly. We studied 80 stable RTX and 82 hemodialysis (HD) patients for 4 years. Systolic and diastolic BP, body weight (BW), cholesterol (Chol), triglyceride (TG), fasting blood sugar (FBS), blood urea nitrogen (BUN), and creatinine (Cr) were measured monthly. Their relationship with environmental temperature and humidity changes were assessed by Pearson tests and Fourier analysis. Ambient temperature and humidity were between 2.5°C to 25.4°C and 68% to 31% in the winters versus summers, respectively.The mean systolic BP in HD patients was 144 ± 18 mm Hg and 140 ± 15 mm Hg during the winter and summer, respectively (P = .004). For the RTX recipients, it was 133 ± 12 mm Hg in winter and 128 ± 19 mm Hg in summer (P < .001). The decrement in diastolic BP in warmer seasons was even more significant than that in systolic BP in both HD and RTX groups. Also, BW in summer was significantly lower than winter among HD (61.1 ± 10 kg vs 63.2 ± 9 kg; P < .001) and RTX (64.4 ± 8 kg vs 65.6 ± 8.4; P < .001) groups. Serum Chol, TG, and FBS did not change significantly during summer and winter in the both groups. Among RTX recipients, BUN level was greater in summer than winter seasons (24.2 ± 15 vs 39.4 ± 20 mg/dL; P = .01), but serum Cr did not differ. The degree of humidity did not correlate with BP, BW, or the above biochemical markers.We conclude that BP and BW are decreased in warmer seasons in both HD and RTX patients. The changes are not accompanied by changes in biochemical markers except for BUN in RTX patients.

Seasonal variation of blood pressure in renal transplant recipients

HYPERTENSION IS a major risk factor for cardiovascular disease, the main cause of mortality in chronic renal failure (CRF). Climatic variations are among the multiple influencing factors on blood pressure (BP) in healthy persons. Few studies have been performed about the effect of temperature and humidity on BP in hemodialysis (HD) patients. They have shown decreased and increased BP at warm and cold seasons, respectively. Changes of BP had a linear correlation with environmental humidity. As we did not find any similar comparative studies in renal transplanted (RTX) and HD patients, we decided to evaluate the effect of environmental temperature and humidity on BP of RTX group.

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.

SEASONAL VARIATIONS IN HEMODYNAMIC AND TEMPERATURE VARIABLES IN HEMODIALYSIS (HD) PATIENTS

Prevention of HD-induced hypotension and control of chronic hypertension are major issues in the care of HD patients. In the general population seasonal variations in blood pressure (BP) are clearly documented, but results in HD patients have been conflicting. In 160 ESRD patients receiving regular HD, we performed a retrospective analysis comparing thirty-five different hemodynamic and temperature (BTM, Fresenius, Bad Homburg, Germany) parameters from treatments during three winter months, with those in the same patients during three summer months. Data captured electronically by the FinesseTM system (iSYMED, GmbH, Butzbach, Germany) was used for the analysis. For each patient mean values for each variable over the three month winter period were matched with their mean values over the summer period. Paired t-tests of the 35 variables were then performed. Average, pre- and post-dialysis pulse, systolic, diastolic and mean arterial BP were significantly higher (p≤0.001) in winter than in summer (e.g. average systolic 137.75±19.66mmHg winter, 132.98±17.12mmHg summer). Ultrafiltration volume was not significantly different between time periods. Minimum and end core temperatures were significantly higher in winter than in summer (end core temperature 36.706±0.238°C winter, 36.624±0.248°C summer, p<0.001), as was average dialysate temperature (36.444±0.241°C winter, 36.367±0.341°C summer, p=0.003). These results are important because they may affect patient outcomes and management. In addition, such differences should be considered in the planning and analysis of longitudinal studies involving these patient variables.

Adult men born in spring have lower blood pressure.

To determine whether there is a relationship between season of birth and adult blood pressure, as a possible early determinant of later blood pressure. We studied 572 men, aged 45-64 years, whose blood pressure was measured in standardized manner as part of a nation-wide survey in Spain. To analyse the seasonal variation in blood pressure, a linear regression was performed, adjusting for age, height, body mass index, occupation and rural or urban residence. We found seasonal variation in mean systolic blood pressure, with maxima in adults born in autumn and winter, and minima in those born in spring and summer. The greatest difference in systolic blood pressure occurred between adults born in spring (134.1 mmHg) and those born in autumn (140.3 mmHg). After adjustment, the difference in means between spring and autumn was 5.9 mmHg (95% confidence interval 0.7 to 11.1 mmHg, P = 0.03). This study demonstrated differences in systolic blood pressures of adult men according to the season of their birth. Although this relationship is compatible with several hypotheses, the difference found between spring and autumn, partially independent of some other factors, might indicate that the extent of early exposure to sunlight is implicated in determining later blood pressure. This needs further investigation.

Lack of seasonal variation in blood pressure in patients on hemodialysis in a North American center

Seasonal variation in blood pressure in patients undergoing hemodialysis in Europe has recently been described. If confirmed, this has important therapeutic, research, and epidemiological implications. All normotensive patients not administered antihypertensive drugs in our unit were studied. Predialysis blood pressures were measured before each dialysis treatment over two 2-month periods, January through February and July through August, in Winnipeg, Canada, a city with one of the most extreme seasonal temperature variations in North America. No difference in blood pressures was found between summer and winter (141 ± 5/75 ± 2 versus 140 ± 4/74 ± 2 mm Hg; P = not significant). Average daily temperatures were –16°C in winter and 23°C in summer. Interdialytic weight gain was the same in both groups. In conclusion, season has no effect on blood pressure in hemodialysis patients in a North American center. Reported seasonal changes in blood pressure in Europe may be related to nonclimatic factors.

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.

Seasonal variation of blood pressure in maintenance hemodialysis.

Seasonal variation in arterial blood pressure has been reported in studies with hypertensive and normotensive subjects. However, the influence of seasonal change on blood pressure of hemodialysis patients has not been reported. To investigate the seasonal variation of blood pressure in Brazil, a tropical country, in patients on hemodialysis. Prospective, cohort study. Dialysis unit of a tertiary medical center (a teaching hospital of the University of São Paulo School of Medicine, São Paulo). Sixteen patients with chronic renal failure undergoing hemodialysis. Blood pressure, body weight, and ambient temperature were evaluated during 6 hemodialysis sessions carried out on 13 days during the four seasons. The diastolic blood pressure was lower in summer than in fall and winter (95 +/- 8 vs 107 +/- 10 and 101 +/- 10 mmHg, respectively; p < 0.05). The same was observed with mean blood pressure (116 +/- 8 vs 130 +/- 11 and 124 +/- 9 mmHg, respectively; p < 0.01). On the other hand, the ambient temperature was higher in summer than in fall and winter (23.0 +/- 1.6 vs 19.5 +/- 3.0 and 15.8 +/- 1.9 degrees C, respectively; p < 0.01). We concluded that for patients with chronic renal failure the blood pressure has a seasonal variation with higher pressures in fall and winter than in summer. Thus, further studies are needed to elucidate the impact of this observation on the adjustment of antihypertensive treatment and on morbidity and mortality in maintenance dialysis patients.

Seasonal change in 24-hour blood pressure and heart rate is greater among smokers than nonsmokers.

In general, blood pressure is higher in winter than in summer, and this factor may be partly responsible for the higher mortality from cardiovascular disease in winter. Cigarette smoking causes an acute pressor response that may interact with this cardiovascular response to cold exposure. We sought to determine whether the seasonal variation in blood pressure and heart rate differs between cigarette smokers and nonsmokers. We evaluated 24-hour ambulatory systolic blood pressure (SBP), ambulatory diastolic blood pressure (DBP), and ambulatory heart rate of 97 healthy men (73 nonsmokers and 24 smokers), 28 to 63 years of age, during the summer and winter, taking indoor temperatures into consideration. Smokers and nonsmokers both had higher daytime ambulatory SBPs and DBPs in winter than in summer (after adjustment for potential confounders). However, the winter increase seen in the smokers was significantly higher for mean daytime SBP (7.3 versus 2.7 mm Hg, P<.01), for mean daytime DBP (4.4 versus 3.1 mm Hg, P=.051), and for ambulatory heart rate (3.9 versus -1.7 beats/min, P<.001). The double product increased from summer to winter (daytime) by 10.53 for smokers and by only 0.11 for nonsmokers (P<.01). There was an independent interaction between season and smoking status that affected SBP (standardized beta=0.66, P<.0001) and DBP (standardized beta=0.32, P<.0001). Smokers have a greater seasonal variation in blood pressure and heart rate than nonsmokers and show a larger increase in the cardiovascular load in winter. Smoking apparently potentiates the cardiovascular response to various climatic conditions. Season should be taken into account in studies of blood pressure and in the diagnosis and treatment of hypertension, particularly among cigarette smokers.

G23 Seasonalvariation of blood pressure and its relationship to ambient temperature in Athens area, Greece

G23 Seasonalvariation of blood pressure and its relationship to ambient temperature in Athens area, Greece

Body mass index is associated with differential seasonal change in ambulatory blood pressure levels

Seasonal changes in blood pressure may be partially explained in thermoregulatory terms. We hypothesized that the seasonal variation in blood pressure is related to body mass index, due to the increased thermoregulatory requirements of leaner individuals. Ambulatory systolic and diastolic blood pressure were monitored once each in summer and winter in 101 healthy normotensive men aged 28 to 63 years. Environmental conditions and body mass index were measured. The population was divided according to quartiles of body mass index. The percentage of subjects with systolic blood pressure increases of more than 10 mm Hg from summer to winter was highest among subjects in the lowest body mass index category, and lowest among those in the highest body mass index category (35% and 8%, respectively, P < .0001). After adjusting for possible confounders, the change in mean systolic blood pressure from summer to winter was inversely associated with body mass index (beta = -0.26, P = .0149). There was no association between diastolic blood pressure change and body mass index. The increase in systolic blood pressure from summer to winter is inversely and independently associated with body mass index. Hypertension research and epidemiological blood pressure studies should take into account the interaction between season, body mass index, and blood pressure. It may also be important to assess hypertension and response to antihypertensive treatment in relation to season, particularly in lean hypertensives.

Seasonal Variation in Blood Pressure in Normotensive Women Studied by Home Measurements

1. The factors influencing the seasonal variation in blood pressure measured at home in normotensive women were examined. 2. Sixteen female subjects (56.3 +/- 7.9 years old, mean +/- SD) measured their blood pressure and pulse rate at home each morning for more than 20 times per month for at least 1.5 years. Blood pressure and body weight were also determined in the office once or twice a month in that period. Monthly means of outdoor and indoor temperatures and daytime length were obtained from the Meteorological Observatory. The single cosinor method was used to evaluate circannual rhythm. 3. We observed a biphasic seasonal variation in self-recorded blood pressure measured at home, environmental temperature and daytime length but found no apparent seasonal variation in body weight and blood pressure measured in the office. The lowest levels of systolic and diastolic blood pressure measured at home were observed in July. The longest daytime length was recorded in June, while the highest outdoor temperature and indoor temperature were recorded in August, indicating that the longest daytime length preceded and the highest environmental temperature lagged behind the lowest level of blood pressure. The shortest daytime length is in December. The lowest outdoor and indoor temperature were observed in January, while the highest levels of self-recorded systolic blood pressure and diastolic blood pressure were in January and December, respectively. Half-amplitudes of self-recorded systolic and diastolic blood pressure were 2.6 +/- 1.0 mmHg and 2.0 +/- 0.8 mmHg, respectively. 4. These findings indicate the importance of a seasonal effect, i.e. daytime length and the environmental temperature, on the blood pressure of individuals.

Seasonal differences in diurnal blood pressure of hypertensive patients living in a stable environmental temperature

To determine whether there is a seasonal variation in blood pressure in hypertensive patients whose daily lifestyle is similar in summer and in winter, and who live almost entirely indoors in a stable environmental temperature. During summer and winter, blood pressure was measured by ambulatory blood pressure monitoring in outpatients with essential hypertension, and environmental temperature was measured by electrothermometer while the patients were awake. The 24-h blood pressure data were analysed after being divided into four groups: morning, afternoon, night-time and sleeping periods. We studied 25 outpatients (mean +/- SD age 57 +/- 12 years) who spend virtually the entire day indoors in both summer and winter. Measurements of systolic and diastolic blood pressure in the morning and night-time periods were significantly higher in winter than in summer (differences of 7.5 +/- 14.7 and 4.1 +/- 8.8 mmHg and 8.2 +/- 14.8 and 4.5 +/- 8.1 mmHg, respectively). Blood pressure measured in the afternoon and during sleeping periods did not differ significantly. No correlation was observed between the seasonal change in blood pressure in the morning and that at night. Environmental temperatures were significantly higher in the morning, afternoon and night-time periods during summer than those during winter. The differences among these periods were not statistically significant. There is a seasonal variation in blood pressure in the morning and night-time periods during winter in hypertensive patients who live essentially indoors in a relatively stable environmental temperature. Pressor factor(s) may differ between morning and night-time periods during winter.

Seasonal variation of blood pressure and its relationship to ambient temperature in an elderly population

To measure the magnitude and timing of seasonal variation of blood pressure and related factors in the elderly living in the community, and to assess their potential impact on cardiovascular risk. Prospective study; from January 1991 to February 1992 blood pressure and other variables were measured at 2-monthly intervals in each subject in their own homes. Ninety-six men and women, age range 65-74 years, recruited from a single group general practice in Cambridge. Seasonal variation of blood pressure, seasonal variation of prevalence of hypertension, seasonal variation of ambient temperature and body mass index. Both systolic (SBP) and diastolic blood pressure (DBP) were greatest during the winter across the whole distribution of blood pressure. There was a fourfold increase in the proportion of subjects with blood pressures > 160/90 mmHg in winter compared with in summer. Regression analysis revealed highly significant seasonal differences in both SBP and DBP. After adjustment for confounding seasonal effects, a 1 degree C decrease in living-room temperature was associated with rises of 1.3 mmHg in SBP and 0.6 mmHg in DBP. Seasonal variation of blood pressure is heightened in older adults and may partly explain the greater cardiovascular disease mortality of elderly subjects during the winter. The blood pressures of elderly people may be inversely related to the ambient temperature. The public health implications of these findings deserve further investigation.

Seasonal Variation of Blood Pressure and Serum Cholesterol in the Elderly

Seasonal Variation of Blood Pressure and Serum Cholesterol in the Elderly

8 Seasonal variation in blood pressure in the elderly

8 Seasonal variation in blood pressure in the elderly