Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Seasonal Variation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10Linked to original sources
PubMedDate not supplied

Seasonal variations of arterial blood pressure in normotensive and essential hypertensives.

Marked seasonal variations in environmental fluid losses and arterial blood pressure (BP) have been observed by us. Factors causing these changes in BP have been investigated. Effect of seasonal variation on BP was studied in 15 controls and 15 essential hypertensives. Mean temperature and relative humidity in well defined 5 local seasons was recorded. Monthly observations included the plasma levels and 24 hours urinary excretion of norepinephrine (NE), epinephrine (E), sodium (Na+) and potassium (K+). Average systolic, diastolic and mean BP were higher in winter season in both the groups (P less than 0.01). In hypertensives this variation was observed despite a significant increase in drug consumption during winter season (P less than 0.001). Both the groups revealed higher plasma levels and daily urinary excretion of NE and E during winter months, (P less than 0.05 - less than 0.001). 24 hrs urinary volume, Na+ and K+ were significantly higher in winter season (P less than 0.05 - less than 0.001). These parameters showed a negative correlation with mean ambient temperature. Increased sympathetic nervous activity as documented by increased NE and E in plasma and urinary, and decreased environmental loss of fluids and sodium may be contributory to this rise in blood pressure during winter season.

Adult↗
PubMed1997

Seasonal variation in childhood asthma hospitalisations in Finland, 1972-1992.

UNLABELLED: All hospital treatment periods caused by asthma in children under 15 years in Finland during 1972-1992 were examined. The data were obtained from the Hospital Discharge Register, covering all hospitalisations in Finland. A total of 59,624 asthma related treatment periods were recorded. The monthly variation in hospitalisations peaked in May (35.6% above the trend) and in autumn and early winter (41.3% above the trend in October), whereas the monthly variations were low in late winter and in summer. The overall profile of seasonal variation was similar in both sexes, although admissions were lower for boys than for girls in winter and higher in autumn. The average monthly deviation was highest in the age group 0-4 years in May, 42.8% above the trend, and highest in the age group 5-9 years in October, 53.9% above the trend. Closer examination of the seasonal variation gives indirect information on possible trigger factors for acute asthma. CONCLUSION: A clear seasonal variation could be observed in childhood asthma hospital admissions, together with age and sex-related differences in this seasonality. Preventive treatment for asthma should be used effectively in order to avoid acute attacks leading to hospitalisation in children who are allergic to birch pollen and also at times of viral respiratory infections.

Acute Disease↗
PubMed1994

Seasonal variation in the diagnosis of Graves' disease.

OBJECTIVE: Heat intolerance is a well known symptom of Graves' disease. Therefore, it is possible that increased ambient temperature could influence the recognition of Graves' disease by unmasking or enhancing the symptom of heat intolerance. Our aim was to determine if there is a seasonal variation in the diagnosis of Graves' disease. DESIGN: A retrospective study. SETTING: A county hospital and clinic. PATIENTS: Two hundred and seven patients with Graves' disease diagnosed from 1985 to 1992. RESULTS: A high correlation was found between the temperature and the number of cases of Graves' disease diagnosed. A larger proportion of patients (68%) was diagnosed during the warmer half of the year, May-October, than during the cooler half. The peak incidence of the diagnosis occurred in May, when 17.4% of the patients were diagnosed. Although the peak average monthly temperature occurs in July, the month of May corresponds to the time of the year when the temperature is making its largest positive change in the month-to-month variation. CONCLUSIONS: Seasonal variations in the temperature can affect the incidence of the diagnosis of Graves' disease. The diagnosis is more common during the months of higher temperature.

Adolescent↗
PubMedDate not supplied

Intensity of long-term treatment with warfarin is influenced by seasonal variations.

In a prospective study, which lasted 1 year and was performed on a large cohort of 800 patients treated at an outpatient anticoagulant clinic, we investigated possible seasonal variations in the intensity of the effect of warfarin treatment. For every season--winter, spring, summer and autumn--the mean prothrombin time reported as an international normalised ratio (INR) and the percentages of INR below 2.0 and above 4.0 were calculated. Significant seasonal variations in mean INR measurements were found, with the lowest values in summer and the highest values in autumn (F = 14.2, p < 0.0001). In addition, a trend toward a higher percentage of INR below 2.0 in summer and above 4.0 in autumn was observed. No significant differences were found between older (>65 years) and younger (<65 years) patients, although there was a trend toward more pronounced variations in younger patients. Consideration of seasonal variations might result in more accurate and safe guidance of warfarin treatment.

Adolescent↗
PubMedDate not supplied

A comparison of seasonal variation in birthweights between rural Zaire and Ontario.

We studied the birthweights in a rural area in Zaire over a ten-year period and found a significant seasonal variation. Also, we reviewed the birthweights in two areas of Ontario over a five-year period. One area was in an Ontario Metropolitan hospital doing more than 2000 deliveries per year. The other was in a rural area in southwestern Ontario doing about 500 deliveries per year. No statistically significant seasonal variation in birthweight was found in Ontario. The seasonal variation in Zaire was associated with change in expenditure of energy by the pregnant women, variation in food availability, and malaria.

Birth Weight↗
PubMed2000

Seasonal variations in internalizing, externalizing, and substance use disorders in youth.

Seasonal variations were assessed in symptoms of internalizing (anxiety and mood), externalizing (attention-deficit/hyperactivity and oppositional defiant disorders), and substance use disorders in youth. This study is based on secondary data analysis of two NIMH-funded epidemiologic-services studies: (a) Alternative Service Use Patterns by Youth with Serious Emotional Disturbance (N=936, ages 9-17); and (b) Methods for the Epidemiology of Child and Adolescent Mental Disorders (N=1285, ages 9-17). Child psychiatric diagnoses were measured by the Diagnostic Interview Schedule for Children. Variables that indicate site of the interview and service system, as well as age, gender, and ethnicity, were used as covariates. Significant annual variations were found in symptom counts of overanxious disorder, obsessive-compulsive disorder, separation anxiety disorder, social phobia, and major depressive disorder, with the estimated nadir in August-October. There may be weak seasonal variations in attention-deficit/hyperactivity disorder with estimated nadir in August, oppositional defiant disorder with estimated nadir in August-September, and marijuana use with estimated zenith in August-September. Significant seasonality in alcohol, other substance use, agoraphobia, and panic disorder was not found. There may be an instrument-specific bias in estimated nadir. Real nadirs may be up to 3 months prior to the estimated nadirs specified above. Findings suggest that seasonality in symptoms should be considered when assessment instruments of childhood psychiatric disorders are developed, as well as when epidemiological and clinical data are collected and analyzed.

Adolescent↗
PubMed1987

Seasonal variations in the effectiveness of urinary chemosignals influencing puberty in female house mice.

Three separate experiments tested whether the seasonal variation in the effectiveness for accelerating or delaying puberty in female conspecifics of male urine, urine from pregnant or lactating females, and urine from females housed in groups is attributable to seasonal changes in the quality of the chemosignals released by the donor mice or to seasonal shifts in the sensitivity to the chemosignals for recipient females or to some interaction between these two factors. Six-by-six cross-classified designs were used with urine collection taking place in alternate months for 1 year and urine treatments with samples from all 6 collection months applied in the same alternate months in the subsequent year. For all three urinary chemosignals the seasonal variations in chemosignal effectiveness were determined to be a function of changes in recipient sensitivity and not of any seasonal shifts in the chemosignals released by donor mice. Seasonal variations in body weight at weaning were also a contributory factor in determining the age of first vaginal oestrus. Covariance analyses revealed that, even after adjustment of the treatment means for the seasonal differences in body weight, there were significant effects on the age of puberty due to seasonal shifts in recipient sensitivity, but not with respect to the month in which the urine was collected.

Animals↗
PubMed2005

G-protein beta3 subunit C825T polymorphism tends to be associated with seasonal variation in young male college students.

This study investigated the relationship between G-protein beta(3) subunit (GNB3) C825T polymorphism and seasonal variation in 189 young male college students. The subjects were genotyped for C825T and were evaluated by the Seasonality Pattern Assessment Questionnaire. The Global Seasonality Score (GSS) between the three genotypes revealed a marginal difference. The heterozygotes showed significantly higher seasonal variations in GSS than the homozygotes. The prevalence of heterozygotes tended to be higher in seasonals compared with normal subjects, although it was not statistically significant. These results suggest that GNB3 C825T polymorphism tends to be related to seasonal variation in mood and behavior in the normal population.

Adult↗
PubMed2005

Lack of seasonal variation in the endoscopic diagnoses of Crohn's disease and ulcerative colitis.

BACKGROUND: Conflicting data have been reported about the seasonal variation of inflammatory bowel diseases (IBD). The purpose of the present analysis was to assess the occurrence of seasonal variations in the endoscopic diagnosis of Crohn's disease (CD) and ulcerative colitis (UC). METHODS: The Clinical Outcomes Research Initiative (CORI) uses a computerized endoscopic report generator to collect endoscopic data from 73 diverse practice sites throughout the United States. We utilized the CORI database to analyze the date-specific occurrence of colonoscopy, as well as the colonoscopic diagnoses of CD and UC. Time trends were analyzed by autocorrelation, linear, and nonlinear regression. RESULTS: Between January 2000 and December 2003, the number of colonoscopies increased 4.1-fold. The proportion of colonoscopies with a CD diagnosis fell by 28%, and the proportion of colonoscopies with a UC diagnosis fell by 50%. The occurrence of neither CD nor UC was shaped by any clear-cut seasonal periodicity. However, the trends of the two diseases revealed strikingly similar patterns with four resembling peaks superimposed on their monthly fluctuations. CONCLUSIONS: Endoscopic diagnosis of IBD is unaffected by any seasonal variation. The decline in the diagnostic rate of colonic IBD may reflect a relative increase in the utilization of colonoscopy for colon cancer screening. The similarity in the monthly fluctuations of both IBD suggests that their incidence or flare-ups may be influenced by identical exogenous risk factors.

Adult↗
PubMed1993

Seasonal variation of aromatic DNA adducts in human lymphocytes and granulocytes.

DNA adducts were measured by 32P-postlabelling in lymphocytes and granulocytes of 75 healthy men exposed occupationally and environmentally to high concentrations of aromatic compounds in the ambient air. Volunteers enrolled in the study were men working at the coke batteries and nonoccupationally exposed inhabitants of Silesia, a highly industrialized region in southern Poland. Blood samples were drawn twice: in February and September 1992. Seasonal variations in the levels of DNA adducts were found only in lymphocytes: 3.6- and 8.7-fold in the occupationally and environmentally exposed groups respectively. In smokers the seasonal variation was as large as 12.8-fold in the environmentally exposed group. No seasonal variations were observed in granulocytes. The observed seasonal variation in the level of aromatic DNA adducts coincided with winter/summer differences in the concentrations of benzo[a]pyrene in the ambient air of Silesia. The study recommends the application of lymphocytes for adduct studies in chronic exposures and provides evidence on the repair of aromatic adducts in lymphocytes.

Benzo(a)pyrene↗
PubMed2003

Seasonal variation in sleeping metabolic rate, thyroid activity, and leptin.

We investigated seasonal variation in sleeping metabolic rate (SMR) and the possible relation to body composition, thyroid activity, and leptin. Twenty-five healthy volunteers were examined four times during the year: in spring (April, May), summer (July, August), autumn (October, November), and winter (January, February). Body composition was determined using a three-compartment model based on underwater weighing and the deuterium dilution method. SMR was measured during an overnight stay in a respiration chamber. A blood sample was taken for the analysis of free and total thyroxine, TSH, and leptin. SMR showed a significant seasonal variation (P < 0.01) with a maximum in winter (4.54 kJ/min) and a minimum in summer (4.34 kJ/min). The amplitude was 0.10 +/- 0.02 kJ/min, and the phase was November 5th. Season explained 17% of the intraindividual variation in SMR. The circannual rhythm in SMR could not be explained by changes in body composition, thyroid activity, or leptin. Interindividual variation in SMR was explained by fat-free mass (P < 0.001) and leptin (P < 0.001).

Adult↗
PubMed2001

Seasonal variation in 1/f fluctuations of heart rate in asthmatic children.

We have reported previously that asthmatic children have a seasonal variation in the power spectrum in the low frequency, LF (0.04-0.15 Hz) and high frequency, HF (0.15-0.6 Hz) bands of heart rate variability (HRV). In recent years, the l/f fluctuations of heart rate (HR) have been used as a novel index of autonomic function from a chronobiological viewpoint. As asthma is a disease with symptoms affected by seasonal chronobiological changes, we examined whether the l/f fluctuations of HR in asthmatic children changed by season. The subjects examined were 87 asthmatic and 104 healthy children. Using a Holter recorder, a 24-h ambulatory electrocardiogram (AECG) was obtained from each subject. The l/f fluctuations of HR during the time awake, the time asleep, and the 24-h period for each of the four seasons were analyzed by the MemCalc system (Suwa Trust). No seasonal variations of HR l/f fluctuations were detected in either the asthmatic or the control group for any of the three periods analyzed. There was a significant seasonal variation in the mean of the normal-to-normal R-R intervals during the 24-h period in the asthmatic children, but not in the healthy children. In the children with asthma, although their HR varied by season, the l/f fluctuations of HR did not.

Adolescent↗
PubMed1981

Seasonal variation in urinary excretion of calcium, oxalate, magnesium and phosphate on free and standard mineral diet in men with urolithiasis.

Seasonal variations of urine volume and urinary excretion of calcium, oxalate, magnesium and phosphate were studied in 118 men with urolithiasis on a standard mineral diet and on free diet. The 24-hour urine volume did not vary by season. There was no significant seasonal variation in the excretion of urinary calcium, oxalate, magnesium or phosphate on a standard mineral diet. While on a free diet the patients' urinary excretion of calcium showed statistically significant seasonal differences between age groups. The seasonal variations in the excretion of urinary oxalate and phosphate were statistically significant on free diet, but did not differ by age. The urinary excretion of magnesium was not affected by season nor age. Dietary intake probably best explains seasonal changes in the urinary excretion of calcium, oxalate and phosphate.

Adolescent↗
PubMed2001

Plasma homocysteine is not subject to seasonal variation.

BACKGROUND: Studies investigating the relationship between plasma total homocysteine (tHcy) and vascular disease usually rely on a single measurement. Little information is available, however, on the seasonal variability of plasma tHcy. The aim of this study was to investigate the seasonal variation in fasting plasma tHcy and related B-vitamin intake and status in a group of people who did not consume fortified foods or take B-vitamin supplements. METHODS: In this longitudinal study, a group of 22 healthy people were followed for 1 year. A fasting blood sample and dietary information were collected from each individual every 3 months, i.e., at the end of each season. RESULTS: There was no significant seasonal variation in plasma tHcy or in B-vitamin intake or status with the exception of red cell folate (significantly lower in spring compared with autumn or winter) and serum folate (significantly lower in spring compared with the other seasons). Although the between-person variation in plasma tHcy was high (47%), the within-person variation was low (11%). This low variation, combined with the low methodologic imprecision of 3.8%, yielded a high reliability coefficient for plasma tHcy (0.97). CONCLUSIONS: Although there was a small seasonal variation in folate status, there was no corresponding seasonal variation in plasma tHcy. The high reliability coefficient for plasma tHcy suggests that a single measurement is reflective of an individual's average plasma tHcy concentration, thus indicating its usefulness as a potential predictor of disease. This, however, needs to be confirmed in different subgroups of the population.

Adolescent↗
PubMed2001

Seasonal variations of T-cell cytokine pattern in peripheral blood from atopic subjects.

Previous studies on the effect of seasonal exposure to the sensitizing antigen on T-cell cytokine pattern from atopic subjects evaluated T-cell cytokine production by titration in the serum or culture supernatants. The purpose of this study was to determine the seasonal variations of T-cell cytokine pattern from atopic subjects at the single-cell level. We examined the interleukin-4 (IL-4) and interferon-gamma expression in peripheral blood CD4 + and CD8 + T cells from 11 subjects with grass-pollen-sensitive allergy before and during the 1999 grass pollen season using a flow cytometric method of intracellular cytokine detection. Eight healthy volunteers served as the control group. Flow cytometric analysis of peripheral blood lymphocytes showed no seasonal variations of IL-4- and interferon-gamma-producing T cells in atopic subjects. However, there was a decreased percentage of IL-4-producing cells among peripheral blood CD4+ and CD8+ T cells from the atopic subjects both during and outside the pollen season in comparison to the controLs. We did not find seasonal variations of T-cell cytokine pattern in peripheral blood from atopic subjects. However, we observed a decreased percentage of IL-4-producing T cells in peripheral blood from these subjects in comparison to healthy controls. These data add to the view of a continuous migration of T helper 2 (TH2) cells from the blood to the tissues of primary allergen exposure.

Adult↗
PubMed2003

Seasonal variations in the binding of [3H]paroxetine to the platelet serotonin transporter sites in African-American cocaine-dependent patients and healthy volunteers.

Although seasonal fluctuations in several indices of serotonin function have been described, little is known about seasonality and serotonergic activity in substance abusers. We investigated whether there were seasonal differences in platelet serotonin transporter sites among cocaine dependent patients and controls. Platelet [(3)H]paroxetine binding, a measure of serotonin transporter sites, was assayed in 141 African-American cocaine-dependent subjects and in 60 race matched healthy volunteers who served as the control group. B(max) (density of serotonin transporter) and K(d) (affinity constant) values of [(3)H]paroxetine binding were compared during spring, summer, fall and winter. Consistent with our previous findings B(max) values were significantly lower in cocaine patients (639 +/- 234) than in controls (906 +/- 225) (t = 7.12, p < 0.001). Moreover, B(max) values showed a significant seasonal variation in controls with the highest values in summer and spring compared with fall and winter (F = 4.47, p < 0.01). However, there were no significant seasonal differences in B(max) values in cocaine patients. K(d) values did not show any seasonal changes in either group. There were no effects of age or gender on seasonal variations in B(max). The study demonstrates a seasonal effect on platelet serotonin uptake in healthy African-American volunteers. The lack of seasonal differences in transporter availability in cocaine patients indicates that the normal seasonal rhythm of serotonergic activity may be disturbed in cocaine abusers. Biological studies that employ platelet serotonin transporter sites as a marker of serotonin function should consider seasonal variations in these markers as a potential source of variance.

Adult↗
PubMed1981

Is there a seasonal variation in oestrogen receptor levels in human breast carcinoma tissues?

The seasonal variation of the incidence of oestrogen receptor-positive mammary carcinomas was investigated in 556 postmenopausal women. In addition, the seasonal variation in receptor concentration in 289 oestrogen receptor-positive breast carcinomas was studied. Neither the proportion of oestrogen receptor-positive carcinomas, nor the concentration of the receptor in the tumours, varied significantly during the year.

Breast Neoplasms↗
PubMed2005

Seasonal variation in amount of unabsorbed dietary carbohydrate from the intestine after breakfast in Japanese subjects.

We previously showed that daytime dim-light exposure has a negative effect on the efficiency of dietary carbohydrate absorption in the evening, whereas evening-time dim-light exposure has a beneficial effect. These results suggest that seasonal changes in the environmental light may affect gastrointestinal activity, and that there might, therefore, be seasonal variation in the efficiency of dietary carbohydrate absorption from the intestine. In order to prove this hypothesis, we measured the amount of dietary carbohydrate unabsorbed from the intestine after a breakfast in healthy female Japanese subjects during the four seasons of the year. We estimated the amount of unabsorbed dietary carbohydrate by the breath hydrogen test, which measures the amount of hydrogen in exhaled air. A 6 g solution of lactosucrose, an indigestible trisaccharide, was used for comparison. Two groups of subjects, 12 subjects in Osaka and 14 subjects in Nagano, were studied in the winter (January to February), spring (April to May), summer (July to August), and autumn (October to November) of 2004. We found the following results: (1) In no season were there any significant differences between the two subgroups in the orocecal transit time of the breakfast and the lactosucrose solution. Nor were there any significant differences in the amount of unabsorbed dietary carbohydrate from the breakfast. (2) Using the pooled data of the total of 26 subjects, there was no significant seasonal variation in the orocecal transit time of the breakfast or the lactosucrose solution. (3) There was a significant seasonal variation in the amount of unabsorbed dietary carbohydrate from the breakfast. (4) The amount of unabsorbed dietary carbohydrate from the breakfast was largest in winter and smallest in autumn. Results in spring and in summer were similar and intermediate between those in winter and autumn. Post hoc multiple comparison tests showed that the amount of unabsorbed dietary carbohydrate in winter was significantly larger than in autumn. (5) In winter, the average ratio of the amount of unabsorbed dietary carbohydrate to the total amount of carbohydrate in the breakfast was about 12%; in autumn it was about 6%. These results clearly show that there is seasonal variation in the efficiency of intestinal dietary carbohydrate absorption among young female Japanese subjects.

Adult↗