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PubMed2000

Seasonal variation in heart rate variability in asthmatic children.

Asthma is a "seasonal disease" with symptoms either aggravated by environmental changes during specific seasons or prevalent at certain times of the year for other reasons. We examined whether the heart rate variability (HRV) of asthmatic children changes by season. The HRV during a portion of one night (00:00-04:00) and day (12:00-16:00) and the entire 24h period (00:00-24:00) during each of the four seasons was analyzed. The data of 95 children with asthma and 106 healthy children, as controls, were assessed. In children with asthma during the 24h period, seasonal variation in the low-frequency (LF) band (0.04-0.15 Hz) and the high-frequency (HF) band (0.15-0.4 Hz) were detected (HF: F=6.81, p=.0003; LF: F=4.18, p= .008). The HF value in the summer was significantly higher than in autumn and spring (Scheffe test: autumn vs. summer, s = 4.46, p < .001: spring vs. summer, s = 2.86, p < .05), while the LF value in autumn was significantly lower than in summer (s = 3.42, p < .01). In the control group, no seasonal variation in HF, LF, or LF/HF was detected. The findings infer the HRV, a surrogate measure of autonomic nervous system function, of asthmatic children is more susceptible to seasonal changes brought about by either endogenous annual rhythms or environmental weather phenomena.

Adolescent↗
PubMed1985

Seasonal variation of in vitro lymphocyte proliferative response to ragweed antigen E.

Seasonal variation of symptoms and IgE response to short ragweed (SRW) allergens is well documented. Clinical symptoms generally parallel the rise and fall of the SRW-pollen count, whereas total and specific-IgE levels peak after the SRW-pollen season with a more gradual return to preseason levels. Because IgE synthesis is under T-lymphocyte control, we tested for seasonal variation in T cell-proliferative response to SRW antigen E (AgE) in vitro. Nine untreated SRW-sensitive and five nonallergic individuals were studied on 15 occasions from June 1981 through May 1982. In vitro proliferative index (SI) to AgE, serum total and specific IgE and SRW-pollen counts were measured; all persons studied kept daily symptom diaries. The mean SI was higher for the atopic group on all 15 sampling dates. The cumulative SI and the daily SI were statistically different between groups before, during, and after pollination. The peak SI for the atopic patients occurred almost 1 2/5 wk after the pollination peak, and the peak IgE antibody levels to SRW occurred at 5 2/5 wk after the pollination peak. We conclude that in vitro responsiveness to AgE is a specific response of allergic individuals and that this response demonstrates a significant seasonal component.

Allergens↗
PubMed2003

Seasonal variation of fibrinogen in dipper and nondipper hypertensive patients.

BACKGROUND: A seasonal variation with higher values in winter has been previously reported in plasma fibrinogen, a recognized marker of the potential risk of myocardial infarction and stroke. The lack of nocturnal decline in blood pressure has also been associated with an increase in cardiovascular events. Accordingly, we have compared the yearly variation of plasma fibrinogen in dipper and nondipper hypertensive patients. METHODS AND RESULTS: We studied 1006 stage 1 to 2 hypertensive patients (482 men and 524 women, 53.0+/-13.4 years of age). Blood pressure was measured every 20 minutes during the day and every 30 minutes at night for 48 consecutive hours. Physical activity was simultaneously evaluated at 1-minute intervals with a wrist actigraph. A blood sample was collected on the same day before starting blood pressure monitoring. The circannual variation of fibrinogen was established for all patients as well as for subgroups of dippers and nondippers (n=513; nocturnal blood pressure decline <10%) by multiple-component analysis. For the whole group of patients, fibrinogen was characterized by a highly significant seasonal variation (P<0.001) with a mean value of 318 mg/dL, double circannual amplitude (extent of predictable change along the year) of 40 mg/dL, and time of peak value in February. Throughout the year, the nondippers showed higher plasma fibrinogen levels than did the dippers (P<0.001). CONCLUSIONS: The elevated plasma fibrinogen levels in nondipper patients appear to be directly related to their increased risk in vascular events, which are more prominent during the late winter months.

Adult↗
PubMed2002

Altitudinal and seasonal variations in the diet of Japanese macaques in Yakushima.

Altitudinal and seasonal variations in the diet of Japanese macaques in Yakushima, southwestern Japan, were studied for 2 years by means of fecal analysis. The altitudinal range of fecal samples collected was 30 m to 1,203 m above sea level, and it was divided into three zones: low-zone forest (0-399 m), middle-zone forest (400-799 m), and high-zone forest (800 m-1,230 m). There was a considerable altitudinal and seasonal variation in the macaques' diet. Seed/fruit and animal matter were eaten more in the lower zones, whereas more fiber and fungi were consumed in the higher zones. In all of the zones, they ate seed/fruits the most in autumn (September-November) and the least in spring (March-April). They ate fibrous food the most in spring and the least in autumn. Macaques relied on seed/fruits heavily in the lower zone for a longer period than in the higher zones. Macaques in the high-zone forest ate almost no seed/fruit foods from March to May. Altitudinal variations in availability of seed/fruit foods seem to have influenced the altitudinal variations in diet. Total basal area of seed/fruit-food trees, species richness of seed/fruit-foods, main seed/fruit-food types available, and annual fleshy-fruit production all decreased with increasing altitude. Both interannual variation and annual cyclicity of diet were found in all zones.

Altitude↗
PubMed1990

[Seasonal variations in house dust mite allergens--significance for children with allergy].

Allergenic proteins of the house dust mites Dermatophagoides pteronyssinus and Dermatophagoides farinae and their major allergens Der p I and Der f I are one of the most significant environmental factors which may facilitate sensitization and allergic airway disease in childhood. In order to measure seasonal variations of mite allergen exposure, we collected mattress dust samples monthly in 13 homes over a period of 1 year. Der p I and Der f I were determined with a sandwich type ELISA. Mite allergen levels were significantly lower from January-June than from July-December (p less than 0.05) which was mostly due to Der p I variations. Only in 6 of the studied homes seasonal variations in mite allergen concentrations according to seasonal variations in outdoor humidity could be observed. In 7 homes mite allergen exposure stayed constant and seemed to depend only on indoor climate factors.

Allergens↗
PubMed1998

Seasonal variation in maxillary antral pseudocysts in a general clinic population.

OBJECTIVES: To determine overall prevalence of maxillary antral pseudocysts and the effect of seasonal variation, allergies, asthma and current smoking status. METHODS: Panoramic radiographs of 1175 dental clinic outpatients were examined. Data on the prevalence of allergies, asthma and smoking status was obtained from the medical records and age- and gender-matched controls. chi-square tests were used to determine the relationship between these factors and seasonal variation in prevalence. RESULTS: Pseudocysts were found in 114 (9.7%) patients. Eleven patients (9.7%) reported a history of environmental allergies, nine (7.9%) were asthmatic and 21 (19.6%) current cigarette smokers. Compared with controls, the association between each of these findings and the presence of pseudocysts was not significant. 44.3% of the pseudocysts were detected in November, December and January compared with only 8.6% in April, May and June: this variation was significant (alpha = 0.01). CONCLUSIONS: The marked increase in the prevalence of pseudocysts during cold winter months supports the concept that seasonal variation may be related to an increased incidence in viremias or irritation from dry forced air heating during this period.

Adolescent↗
PubMed1984

Analysis of the secular trend and seasonal variation of measles mortality rate in Taiwan.

The secular trend and seasonal variation of measles mortality rate in Taiwan from 1959 to 1981 were analyzed through multiple regression analyses. A significant downward trend with a regular two-year cyclic fluctuation was observed before and after the implementation of a mass vaccination campaign, and the difference between odd and even years was greater in later years than in earlier years. There was a characteristic unimodal pattern of seasonal variation which peaked in the months of late spring or early summer, and measles deaths were found more clustered in epidemic years than in nonepidemic years. While 94.3% of the total variation of annual measles mortality rate could be explained by calendar year, two-year cycle, and their interaction; 87.6% of the total variation of monthly measles mortality rate could be explained by calendar year, two-year cycle, month, and the interaction between two-year cycle and month. The implication and application of such multiple regression analysis of temporal components of measles epidemiology are discussed.

Child↗
PubMed1975

Seasonal variations in the composition of urine in relation to calcium stone-formation.

1. A retrospective cross-sectional study was carried out on data derived from single 24 h urine collections from 246 male idiopathic calcium stone-formers. 2. The daily urine volume and pH and the exretions of calcium, oxalate, phosphate, creatinine and magnesium were related to the time of year when the urine was collected, and the saturation of urine with calcium oxalate and octocalcium phosphate calculated for each month. 3. There were significant seasonal variations in the urinary excretion of calcium and oxalate, each showing a maximum during the summer months and a minimum in the winter. There was no significant seasonal variation in urinary pH, volume, creatinine, phosphate or magnesium. 4. There was a significant increase in the saturation of urine with calcium oxalate and a trend towards higher saturation levels of octo-calcium phosphate in the summer. These changes were dependent only on the seasonal variation in urinary calcium and oxalate and not on urine volume. 5. A retrospective study of the seasonal incidence of stone episodes among these 246 stone-formers showed that the rate of stone passage per month was 50% higher in the summer than in the winter. There was no significant seasonal variation in the incidence of stones removed surgically.

Calcium↗
PubMed1998

Sex differences in seasonal variations in P300.

Previous reports of seasonal variations in P300 were based on cross-sectional observations of subjects tested at different times of the year. In this study, we tested three groups of subjects in each of two seasons: winter and spring, spring and summer, and summer and winter. We found winter or spring maxima in auditory and visual P300 and visual slow wave. This pattern of results, with the amplitude of P300 being inversely related to the amount of sunlight in a season, supports the hypothesis that the allocation of processing resources varies across the seasons. Our results also suggest a trend for an increased sensitivity of women, as compared with men, to seasonal influences on P300. Although our findings do not provide strong evidence that P300 varies systematically as a function of season, seasonal factors appear to affect cognitive processing (as indexed by P300) differentially in men and women.

Adolescent↗
PubMed1996

Seasonal variations in office, home and 24 h ambulatory blood pressure in patients with essential hypertension.

OBJECTIVE: To study the influence of seasons on blood pressure in ordinary circumstances. DESIGN AND METHODS: We examined seasonal variations of home and 24 h ambulatory and office blood pressures in outpatients with essential hypertension. Office, home and ambulatory blood pressures of 50 outpatients with essential hypertension were recorded in 1993. The subjects were 26 women and 24 men, aged 59.3 +/- 1.1 years (mean +/- SEM). Office blood pressure was measured monthly by physicians. Home blood pressure was measured every day by the patients in the morning and evening. Ambulatory blood pressure was recorded every 30 min in summer and in winter. The order of ambulatory blood pressure monitoring was randomized. The daytime and night-time blood pressures were calculated according to the true waking and sleeping times of the individual patients. RESULTS: Both office and home blood pressures showed significant seasonal variations. The winter-summer differences in office and home blood pressures were 4.7 +/- 1.3/ 3.3 +/- 0.9 and 5.9 +/- 1.1/2.7 +/- 0.6 mmHg, respectively. They were not influenced by the presence of antihypertensive agents. The winter-summer difference was also significant for daytime ambulatory blood pressure (3.5 +/- 1.4/ 2.5 +/- 0.8 mmHg), but not for night-time ambulatory blood pressure (-2.9 +/- 1.7/-1.2 +/- 1.0 mmHg) or average 24 h blood pressure (1.5 +/- 1.3/1.2 +/- 0.7 mmHg). There were no significant differences in the waking and sleeping times between the two seasons. CONCLUSIONS: Office, home and daytime ambulatory blood pressure levels were higher in winter than they were in summer in patients with essential hypertension. However, the seasonal variations in average 24 h blood pressure may be small because of the lack of changes in night-time blood pressure.

Adult↗
PubMed2005

Seasonal variations in photosynthesis of Picea morrisonicola growing in the subalpine region of subtropical Taiwan.

From January 1999 to May 2001, we investigated seasonal variations in the photosynthetic capacity of Taiwan spruce (Picea morrisonicola Hay.) growing in the subalpine region of subtropical Taiwan (23 degrees 29' N, 120 degrees 53' E, 2600 m a.s.l.). Photosynthetic capacity (near light-saturated net photosynthetic rate, Pnsat, chlorophyll fluorescence (Fv/Fm) and soluble protein concentration of needles all increased from mid or late spring to early winter. Even when minimum air temperature of the measuring day dropped to near 0 degrees C, Pnsat remained at about 20% of the highest value observed in winter. There was a curvilinear relationship between Fv/Fm and the minimum or mean air temperature of the measuring day. The increase in Fv/Fm with temperature was slowed when the daily mean air temperature was above 7 degrees C, or the minimum air temperature was above 3 degrees C; however, when air temperatures dropped below these values, Fv/Fm varied sharply. Seasonal variations in Pnsat paralleled those in Fv/Fm and needle soluble protein concentration. In early or mid spring when air temperature and Fv/Fm increased, Pnsat and soluble protein concentration remained low. Multiple regression analysis showed that seasonal variations in Pnsat were affected by Fv/Fm, air temperature and needle soluble protein concentration, and the multiple regression equation could be used to estimate Pnsat in different seasons. We conclude that the decrease in photosynthetic capacity of Taiwan spruce in winter and its subsequent recovery in spring were mainly caused by photoinhibition and its reversal, and changes in needle soluble protein concentration. Another possible explanation for the delayed recovery of photosynthetic capacity in spring may be associated with the slow increase in needle soluble protein concentration.

Chlorophyll↗
PubMed1987

Seasonal variation in blood biochemistry of long-term captive Mediterranean tortoises (Testudo graeca and T hermanni).

Reference values for five blood chemistry parameters in 18 Mediterranean tortoises of two species, Testudo graeca and T hermanni, were determined on up to 10 occasions during the year. Statistically significant seasonal variations were demonstrated in blood urea and blood glucose. Seasonal variations were demonstrated in blood urea and blood glucose. Seasonal variations in total plasma proteins, lipids and cholesterol, however, were limited to gravid females. The study also suggested that three energy sources were available to the tortoise during hibernation, lipids stored in the fat body, endogenous protein degradation and glucose derived from hepatic glycogen.

Animals↗
PubMed1996

Seasonal variation in community-acquired pneumonia.

Seasonal variation in the incidence of disease in general, and of infectious diseases in particular, is vitally important information for epidemiologists and for clinicians who deal with these diseases. In relation to community-acquired pneumonia (CAP), the seasonal distribution of the disease and, in particular, of each of the specific aetiological agents is important. All 346 adult patients who were admitted to a regional hospital in southern Israel for CAP over a period of 1 year were included in a prospective study. As part of the study, a comprehensive diagnostic work-up was performed to identify the specific causative agents for CAP. The study findings were analysed and are presented in terms of the seasonal distribution of the disease. Thirty four percent of CAP cases occurred in the spring and only 18% in the autumn (p = 0.036). Respiratory viruses CAP were predominant in the winter and spring (p = 0.009), whilst Mycoplasma pneumoniae CAP reached its peak incidence of 41% in the spring compared with 15% during the winter months (p = 0.054). No significant seasonal predominance was observed for the other specific aetiological agents of CAP. In 58% of the CAP patients who were hospitalized in the autumn we identified a pneumococcal aetiology, whilst this agent was found in only 32% of the cases in the winter. In contrast with popular public opinion, winter with its low temperatures is not the main reason for the development of community-acquired pneumonia. Most of the specific aetiologies for community-acquired pneumonia, with the exception of respiratory viruses and Mycoplasma pneumoniae, have no seasonal predilection.

Community-Acquired Infections↗
PubMed2000

Sex differences, but no seasonal variations in the hippocampus of food-caching squirrels: a stereological study.

Recent studies have described sex differences in the relative size of the hippocampus that are associated with sex differences in space use in birds and short-lived mammals. A correlation between spatial learning and increased hippocampal volume has also been demonstrated in food-caching animals. Such results suggest that sexually dimorphic spatial learning (sex differences in space use during the breeding season) and seasonal variations in food-caching behavior (spatial memory for cache locations) might correlate with morphological changes in the hippocampus of adult long-lived mammals. We used modern stereological techniques to examine the volume and neuron number of the structures forming the hippocampal complex (dentate gyrus, CA3, and CA1) of wild adult eastern gray squirrels (Sciurus carolinensis) throughout the year. We observed differences in brain size between samples collected at different times of the year (October, January, and June). Our analysis showed sex differences, but no seasonal variations, in the volume of CA1 stratum oriens and stratum radiatum. There were no sex differences or seasonal variations in the relative volume or the number of neurons of any other layer of the structures forming the hippocampal complex. These results confirm the existence of sex differences in the structure of the hippocampus; however, this sexual dimorphism does not vary seasonally in adulthood and is likely to result from developmental processes. These results do not support the hypothesis that seasonal variations in food-caching behavior might correlate with morphological changes, such as variations in volume or neuron number, in the hippocampal complex of adult long-lived mammals.

Age Factors↗
PubMed1999

Seasonal variation of blood cholesterol levels: study methodology.

This manuscript provides a description of the methodology used in the Seasonal Variation of Blood Cholesterol Levels (SEASON) study, with the intent of informing the scientific community of the available data sets and to invite a dialogue with scientists in complementary fields. The primary aim of the SEASON study is to describe and delineate the causes of seasonal variation of blood lipid levels in the general population. This research project is designed specifically to systematically collect and analyze a number of important variables necessary to study the role of seasonality in blood lipids and relevant covariates.

Adult↗
PubMedDate not supplied

[Seasonal variation in mortality in the city of Valencia, Spain].

OBJECTIVE: To study the seasonal variation in mortality for all causes, grouped according to age and sex, within the city of Valencia during the period 1976-1990 and its relationship with air temperature. MATERIAL AND METHODS: This is an ecological study using monthly global mortality and mean atmospheric temperature statistics for the city of Valencia, Spain between 1976 and 1990. The principal variable has turned out to be mortality for all causes. Mortality rates have been determined for specific age groups (0-4, 35-49, 50-64, 65-74 and > or = 75), as well as for both genders, within the city of Valencia for each of the 180-month period of investigation. Average monthly mortality data has been obtained and the percentage variation has been calculated. Graphical analysis has been used to examine the seasonal variation in mortality and in order to discern the nature of any relationship between atmospheric temperature and mortality. The regression line has been adjusted using the Loess method (smoothed regression motive, locally pondered). The association between mean temperature and mortality has calculated by means of multiple regression analysis controlling for trend, seasonality and period effect. RESULTS: A clear seasonal pattern emerges with mortality peaking during the Winter months and dipping during the Summer and early Autumn. The increase in mortality seen during the month of January came to 27.7% of the total mortality for females and 19.5% of the total mortality for males. By age groups, this increase was greater in the 75-plus age group. Graphically, the relationship between temperature and mortality has a V-shape appearance, with a lower mortality level when the mean daily temperature for the month in question is approximately 23 degrees Celsius. Based on this relationship, two complementary.

Adult↗
PubMedDate not supplied

Circadian and seasonal variations in iodine excretion in children with and without endemic goiter.

The urinary iodine excretion was measured in 193 children 11 +/- 1.5 years of age living in the endemic goiter area of Dîmboviţa, Romania. One hundred and thirty four of the children showed some degree of endemic goiter, 59 showed none. All children followed a diurnal activity pattern with rest during the night. They received their usual iodine supplement of 1 gm potassium iodide once a week during the school year (which included the time of all measurements made). Urine was collected in six 4-hour samples over a 24-hour span. The examinations were conducted during the months of March, June, September and December. Iodine was determined by an automated ceric ion arsenic acid method using a Technicon Autoanalyzer. Circadian and seasonal variations of urine volume and iodine excretion were statistically verified by the cosinor technique and the seasonal variations also by one way analysis of variance using the circadian means as input. A comparable circadian rhythm of iodine excretion was found in the children with and without endemic goiter, with an acrophase during the evening (20:16 with a 95% C.I., from 19:32 to 21:04). The circadian rhythm in iodine excretion has to be taken into account whenever an estimate of the 24-hour excretion is attempted from a sample covering less than the entire 24-hour span. There was a statistically significant seasonal variation of the 24-hour iodine excretion in the boys with and without endemic goiter and in the group as a whole. The 24-hour iodine excretion during March was 102 +/- 6 mcg, during June 81 +/- 4 mcg, during September 79 +/- 3 mcg and during December 102 +/- 7 mcg. The average 24-hour iodine excretion pooled over all seasons was 91 +/- 3 mcg/24 hrs in the children with and 91 +/- 5 mcg/24 hrs in the children without endemic goiter. During March and December the iodine excretion indicates an iodine intake not usually associated with a high prevalence of endemic goiter. However, during the months of June and September (and presumably even more during the months of July and August when during summer vacation no iodine supplementation was given in school) the 24-hour iodine excretion indicates some degree of iodine deficiency. The seasonal variation in urinary iodine excretion thus points to a time when increased iodine prophylaxis may be of value.

Child↗
PubMed2004

Seasonal variation of sudden infant death syndrome in Hawaii.

OBJECTIVE: To test whether the sudden infant death syndrome (SIDS) rate displays the universal winter maximum and summer minimum in Hawaii where there is no appreciable seasonal variation of temperature. DESIGN: The null hypothesis is tested that there is no seasonal variation of necropsied SIDS in Hawaii. The numbers of live births and SIDS cases by month for the years 1979 to 2002 were collected and the monthly SIDS distribution is predicted based on the age at death distribution. SETTING: The state of Hawaii, located in the midst of the Pacific Ocean, has a semi-tropical climate with temperatures fluctuating diurnally as 25 +/- 5 degrees C throughout the year. Therefore homes are unheated and infants are not excessively swaddled. The Hawaii State Department of Health maintains vital statistics of all infant births and deaths. MAIN RESULTS: The results reject the null hypothesis of no seasonal variation of SIDS (p = 0.026). An explanation for the seasonal effect of the winter maximum and summer minimum for Hawaiian SIDS is that it arises from the cycle of the school session and summer vacation periods that represent variable intensity of a possible viral infection vector. SIDS rates in both Hawaii and the United States increase with parity, also indicating a possible role of school age siblings as carriers. CONCLUSIONS: The winter peak of the SIDS in Hawaii is support for the hypothesis that a low grade viral infection, insufficient by itself to be a visible cause of death at necropsy, may be implicated as contributing to SIDS in vulnerable infants.

Age Distribution↗