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 37 records · Page 2Linked to original sources
PubMed2000

Seasonal variation in mortality in Scotland.

BACKGROUND: Seasonal patterns in mortality have been recognized for many years. This study assesses seasonal variation in mortality in Scotland between 1981 and 1993 and considers its association with socioeconomic status and outdoor temperature. METHODS: Lagged Poisson regression analysis of numbers of deaths and average weekly temperature with adjustment for serial autocorrelation and influenza epidemics. RESULTS: There was significant seasonal variation in weekly death rates with a difference of about 30% between a summer trough and a winter peak. This variation was principally attributable to respiratory disease, cerebrovascular disease and coronary artery disease. Seasonal variation in mortality fell from around 38% in 1981-1983 to around 26% in 1991-1993. There was no clear evidence of a relationship between socioeconomic status and seasonal mortality, however the extent of the fall in seasonal variation was greater in deprived areas than in affluent areas. Overall, a 1 degree C decrease in mean temperature was associated with a 1% increase in deaths one week later. The lag in this relationship varied by cause of death and underlying temperature. CONCLUSIONS: Seasonal variations in mortality and the relationship between temperature and mortality are a significant public health problem in Scotland. It is likely that the strength of this relationship is a result of the population being unable to protect themselves adequately from the effects of temperature rather than the effects of temperature itself.

Adolescent↗
PubMed1992

Seasonal variation in gonorrhoea.

Seasonal variations in the incidence of gonorrhoea were observed in the 1970's with a peak in the third quarter of the year and a trough in the first and fourth quarters. The aim of this study was to determine what, if any, seasonal trends were present in Scotland and Lothian between 1984 and 1989 and postulate mechanisms to explain our observations. We observed a change in the previously reported pattern with regular peaks of infection in the first and third quarters of the year for Scotland but no regular trend in the Lothian region. The most likely explanation for the observed trends are changes in sexual behaviour related to summer vacations and seasonal work patterns but other unidentified factors probably also contribute.

Female↗
PubMed1998

Characteristics of UVA-induced delayed tanning: seasonal variation.

We studied seasonal variation in UVA-induced delayed tanning and compared it to that in UVA + B-induced delayed tanning. The minimal tanning dose (MTD) and the minimal melanogenic dose (MMD) were determined one week after UVA exposure or UVA + B exposure, respectively. The MTD determined in the summer (June to August) was significantly higher than that in winter (December to February). In addition, while MTD in the winter correlated well with skin color, there was no correlation between MTD and skin color in summer. MTD tended to correlate with self-reported tanning history at the initiation of tanning in the winter, but they were not correlated with each other in the summer. The MMD measured in the summer was significantly lower than that in the winter. MMD correlated well with skin color in both seasons; the lighter the skin, the smaller the MMD. Also, a correlation was detected between MMD and self-reported tanning history. These results suggest that the susceptibilities of delayed tanning to UVA and UVA + B are affected by different factors.

Adult↗
PubMed2006

Seasonal variation in paroxysmal atrial fibrillation documented by 24-hour Holter electrocardiogram.

BACKGROUND: The incidence of various cardiovascular diseases is known to exhibit seasonal variations, but seasonal patterns of paroxysmal atrial fibrillation (AF) have not been well characterized. OBJECTIVE: The objective of this study was to determine whether seasonal variation affects the incidence of paroxysmal AF and whether this pattern is affected by patient age. METHODS: We identified 258 paroxysmal AF episodes in 237 patients (age 65 +/- 14 years, mean +/- standard deviation; age range 16-95 years) among 12,390 consecutive 24-hour Holter electrocardiogram recordings obtained from 2001 to 2005 at our institute. Seasonal variations were analyzed by both month and by season. The relative risk (RR) of AF for each period was determined as being high or low in relation to the overall mean incidence. The association among clinical covariates and risk of paroxysmal AF was tested by logistic regression analysis. RESULTS: The incidence of paroxysmal AF was highest in September (RR = 1.40, 95% confidence interval [CI] 1.36-1.44) and lowest in June (RR = 0.52, 95% CI 0.50-0.54), with an RR difference of 63% (P < .001) among all patients. Patients aged > or =65 years demonstrated a peak incidence in September (RR = 1.46, 95% CI 1.41-1.51) and a minimum in June (RR = 0.55, 95% CI 0.52-0.58), while those aged <65 years showed a peak incidence in December (RR = 1.33, 95% CI 1.27-1.39) and a minimum in June (RR = 0.49, 95% CI 0.45-0.53). The incidence of paroxysmal AF also showed an autumn peak (RR = 1.21, 95% CI 1.16-1.27) and a summer minimum (RR = 0.66, 95% CI 0.62-0.70), with an RR difference of 53% (P < .001) among all patients. This seasonal variation in paroxysmal AF did not differ between patients of different age ranges. Clinical covariates including underlying disease or medications did not influence the monthly or seasonal variation in paroxysmal AF. There was a significant inverse relationship between the incidence of paroxysmal AF and the length of daylight in patients aged <65 years (r = -0.57, P < .05). CONCLUSION: There was a significant seasonal variation in paroxysmal AF, with maximum and minimum incidences in autumn and summer, respectively, and this pattern was not age dependent.

Adolescent↗
PubMed2003

Seasonal variation in meningococcal disease in Denmark: relation to age and meningococcal phenotype.

Seasonal variation has been shown in meningococcal disease (MD), but it is not known whether seasonal variation depends on age, gender and meningococcal phenotype. Based on complete registration of MD in North Jutland County, Denmark, during 1980-1999 (n = 413 cases), a Poisson regression model of a sinusoidal form was used to examine: (i) whether the seasonal variation in MD follows a sinusoidal pattern; (ii) the magnitude of seasonal variation in MD; and (iii) whether seasonal variation is related to age and gender and meningococcal phenotype. The peak-to-trough ratio (PTR) was used as a measure of the magnitude of seasonal variation. An overall seasonal variation in MD was found [PTR 2.0, 95% confidence interval (95% CI) 1.5-2.6]. There were differences between age groups and between phenotypes, but not between genders. The highest PTRs were observed for the age groups 5-9 y (PTR 4.9, 95% CI 2.1-11.9) and 10-14 y (PTR 3.7, 95% CI 1.4-9.7). No seasonal variation was found for children < 1 y (PTR 1.4, 95% CI 0.6-3.2) or teenagers 15-19 y (PTR 1.6, 95% CI 0.8-3.0). Among phenotypes the highest PTR was observed for C:2a:P1.2,5 (PTR 3.8, 95% CI 1.3-11.2). Thus, seasonal variation depended on age and meningococcal phenotype, the most pronounced seasonality being in 5-14-y-olds and in cases with phenotype C:2a:P1.2,5.

Adolescent↗
PubMedDate not supplied

Seasonal variation of slipped capital femoral epiphysis in the United States.

Seasonal variation in the onset of symptoms of slipped capital femoral epiphysis (SCFE) has been described. The author examined seasonal variation of hospital admissions for SCFE using a national database and compared seasonal variation between the northern and southern United States, between girls and boys, and between black and white children. Significant seasonal variation was found in the North in both boys and girls, but there was less seasonal variation among blacks than among whites. Some seasonal variation was present in the South, but it did not reach the level of statistical significance. Although the cause of seasonal variation in SCFE remains unknown, the effect differs by latitude and skin pigmentation, suggesting a possible link to impaired vitamin D synthesis.

Child↗
PubMed1994

Seasonal variation in the frequency of Helicobacter pylori infection: a possible cause of the seasonal occurrence of peptic ulcer disease.

OBJECTIVES: The seasonal variation of duodenal ulcer disease and its complications have been repeatedly demonstrated in Israel by several independent studies. The aim of this study was to determine possible seasonal variations in the occurrence of H. pylori infection among dyspeptic patients in Israel. METHODS: All 14C-urea breath tests performed in dyspeptic patients at the gastroenterology department in the Tel Aviv Medical Center from January 1991 to December 1992 were reviewed. The monthly variation in the proportion of patients with H. pylori infection was determined, and compared with that of an unrelated 14C-cholyl-glycine breath test. RESULTS: Altogether, 702 patients were examined, and 371 (52.8%) of them were found to be infected with H. pylori. During summer months (July-September), a significant decrease in the percentage of patients infected with H. pylori was found, compared with winter months (December-January, 42.3% vs. 60.9%, p < 0.007). No seasonal variation was found in the results of 14C-cholyl-glycine test. The fluctuations in H. pylori infection were highly correlated with the seasonal occurrence of peptic ulcer disease in Israel. CONCLUSIONS: The frequency of H. pylori infection in dyspeptic patients in Israel is significantly increased during the winter months and decreased in the summer. This seasonal variation is identical to that found in duodenal ulcer disease. Thus, the seasonal variation of peptic ulcer disease could be explained by H. pylori infection, as seen in other communicable infectious diseases.

Breath Tests↗
PubMed1992

[Seasonal variation of intraocular pressure after trabeculotomy].

The author reviewed the seasonal variation of intraocular pressure (IOP) in primary open angle glaucoma or late type developmental glaucoma to investigate possible relationships among seasonal variation of IOP, progression of visual field defects and the follow-up period between 53 eyes of 39 subjects with successful trabeculotomy (trabeculotomy group) and 45 eyes of 31 subjects with only medication (no operation group). IOPs in both groups were inclined to be low in summer and high in winter. Maximum seasonal variation of IOP and standard deviation of IOP during all follow-up periods which showed the degree of seasonal variation of IOP had no significant difference between the trabeculotomy group and the no operation group. These results showed that seasonal variation of IOP was not reduced even by successful trabeculotomy. The maximum seasonal variation of IOP and standard deviation of IOP had a tendency to be bigger in cases with progression of visual field defects than in cases with no progression of visual field defects, in both groups. Therefore, seasonal variation of IOP may be an important factor influencing the progression of visual field defects.

Follow-Up Studies↗
PubMed1991

Seasonal variation in growth during growth hormone therapy.

Seasonal variation in growth of normal children has been well described, although the mechanism by which it occurs has not been elucidated. The growth of 52 growth hormone-deficient children treated with synthetic human growth hormone was analyzed. A similar seasonal variation was observed, with mean (+/- SEM) peak growth occurring in the summer (8.2 +/- 0.3 cm/y) and winter (7.7 +/- 0.2 cm/y), and trough growth occurring in the autumn (6.9 +/- 0.3 cm/y). Forty-seven percent of subjects grew minimally during the autumn, and only two children showed peak growth in that season. Individual variations between maximal and minimal growth seasons amounted to 3.5 +/- 0.3 cm/y. The seasonal pattern was statistically significant for the group as a whole, for the prepubertal subgroup, and for the boys. The variation persisted when the first year of treatment was excluded to avoid bias of the initial growth spurt. The season of onset of therapy did not affect total growth during the first year. The demonstration of a seasonal pattern in growth of these children suggests that the seasonal variation may be mediated by peripheral rather than central factors. Paired clonidine-provoked growth hormone levels and an integrated concentration of 24-hour growth hormone levels and serum levels of insulinlike growth hormone I measured in a control group of normally growing children were also analyzed and showed no seasonal variation. This further suggests that peripheral rather than central factors are responsible for the seasonal variation in children's growth.

Adolescent↗
PubMed2000

[Seasonal variations in the diagnosis of hyperthyroidism].

Seasonal variations in the frequency of thyrotoxicosis are known for a long time. Both, variations in the temperature and in the iodine supplementation are believed to affect the incidence of the diagnosis of hyperthyroidism. Seasonal variation of the incidence of hyperthyroidism was investigated before and after increase of salt iodination in 1990/1991. In the period from January 1987 to December 1995 hyperthyroidism was diagnosed for the first time on 4711 patients in our department. This population was subdivided according to etiology (Graves' disease, autonomous nodular goiter) and grade of hyperthyroidism (preclinical or clinical form). The so formed groups were divided according to the month of diagnosis into further 12 subgroups. Significant differences in month to month variation were found in the patients suffering from Graves' disease and autonomous nodular goiter with preclinical hyperthyroidism after increased iodine supplementation. The peak incidence of the diagnosis occurred in June, July, and August. Our results indicate that improved iodine supplementation may be the main cause of seasonal variations in the incidence of thyrotoxicosis.

Austria↗
PubMed1992

[Seasonal variation of mean birth weight in Okinawa].

Seasonal variation of mean birth weight in Okinawa was examined by a traditional time-series analysis, which decomposed the variation in a series into trends, seasonal variations, other cyclic changes, and remaining irregular fluctuations, based on the data in Vital Statistics from January 1974 to December 1983. The seasonal index of mean birth weight showed a peak in winter to early spring and a bottom in summer with statistical significance. Previous reports have revealed that the gestational period is the most important factor associated with birth weight. Therefore, we carried out the time series analysis for the mean gestational period but could not observe seasonal periodicity in it. On the other hand, mean birth weight at 40 gestational weeks was significantly lower in summer. These results suggest that factors other than the gestational period, such as infectious diseases, nutritional conditions and so on, might play important role in seasonal variations of mean birth weight in Okinawa.

Birth Weight↗
PubMed2006

Seasonal variation in blood pressure of patients on continuous ambulatory peritoneal dialysis.

BACKGROUND: A seasonal variation in blood pressure (BP) has been observed in hemodialysis and renal transplant patients. However, this phenomenon in continuous ambulatory peritoneal dialysis (CAPD) patients, whose hemodynamics are different from hemodialysis patients, has not been reported before. In addition, the contribution of extracellular water (ECW) in the seasonal variation in BP is not clear. METHODS: All stable CAPD patients (n = 122) dialyzed in a single center from January 1, 2003 to December 12, 2004 were studied. Systolic blood pressure (SBP), diastolic blood pressure (DBP), weight and ECW (by bioimpedance analysis) were measured in every patient. Climatic data were obtained from the Beijing Weather Bureau. These data were pooled together and grouped according to the calendar month. RESULTS: In general, an apparent seasonal variation in BP was observed in CAPD patients. BP began to decrease from spring and reached the lowest level in summer, then increased from autumn and reached its peak in winter. The seasonal variation in BP in male patients was similar to that in female patients, but in comparison to non-diabetic patients there was no apparent seasonal variation in the BP of diabetic patients. SBP and DBP negatively correlated with the average atmospheric temperature (r = -0.768, p < 0.001 and r = -0.764, p < 0.001, respectively). BP also negatively correlated with rainfall and humidity, but this correlation disappeared when temperature was controlled in partial correlation analysis. Weight and ECW fluctuated throughout the year but showed no seasonal variation. CONCLUSION: On the whole there was an apparent seasonal variation in blood pressure in CAPD patients. As opposed to non-diabetic patients, there was no apparent seasonal variation in BP in diabetic patients. The seasonal variation in BP was influenced more by temperature than rainfall and humidity, and the change in ECW was not seasonal, suggesting that other mechanisms such as total peripheral resistance might play a more important role in this phenomenon.

Aged↗
PubMed1998

Seasonal variation in mortality in Moscow.

BACKGROUND: Seasonal variation in mortality has been investigated in many countries but not, until recently, in Russia. There are some grounds for suspecting that it may differ in Russia from what is seen in western countries. This paper explores patterns of seasonal variation in mortality in Moscow between 1993 and 1995. METHODS: Analysis was based on individual data on deaths occurring in Moscow between January 1993 and December 1995, grouped by four-week period and by calendar month and on mean monthly temperature in Moscow for the same period. Crude, smoothed and deseasonalized trends were inspected. Auto-correlation functions were estimated and deaths were regressed against temperature. RESULTS: As in other northern hemisphere countries, there is a winter excess of deaths but this is much smaller than in many western countries. It is restricted to some causes of death, such as ischaemic heart disease and cerebrovascular disease, and is associated with low temperature. In contrast, there is a marked summer increase in deaths among young people, especially from accidents and other deaths associated with alcohol consumption. Over the three-year period studied, there was an initial underlying increase in alcohol-related deaths that subsequently fell, coinciding with a previously observed increase in life expectancy. CONCLUSIONS: It is possible that the low level of excess winter mortality reflects warmer indoor environments than in the west. The seasonal variation of deaths among young people reinforces evidence of the important role of alcohol in the Russian mortality crisis.

Accidents↗
PubMed2000

Seasonal variation in hospital admission for bipolar disorder, depression and schizophrenia in Tasmania.

OBJECTIVE: Seasonal variation has been reported for both affective disorders and schizophrenia. The current study examines seasonal variation in admissions in schizophrenia, depression and bipolar disorder in Tasmania, the southernmost state of Australia. METHOD: All admissions with a diagnosis of schizophrenia, bipolar disorder and depression in Tasmania between 1983 and 1989 were examined for evidence of seasonal variation in admission patterns. RESULTS: Using the modified Kolmogorov-Smirnov statistic defined by Freedman no significant seasonal variation was found in admissions with diagnoses of mania, depression or schizophrenia. There was a significant seasonal variation in admissions with schizoaffective disorder (winter peak). CONCLUSION: There is no significant seasonal variation in admissions with schizophrenia, depression or bipolar disorder in Tasmania. This may be due to a combination of geographical location and the stringent test of seasonal variation used in the current study.

Bipolar Disorder↗
PubMed2000

Seasonal variation of violence in Norway.

OBJECTIVE: Seasonal variations of violence have been the subject of some controversy. Norway, situated between latitudes 58 degrees and 72 degrees N, has considerable seasonal variations of light and provides a good opportunity for studies of seasonality. METHOD: The monthly numbers of police reports of violent incidents in 1991-1997 were obtained for the entire Norwegian population of 4,450,000 inhabitants and separately for each of seven Norwegian cities at different latitudes. RESULTS: A total of 82,537 episodes of violence were recorded. There was a significant variation in violent incidents between months, with a minimum daily frequency of 28.7 in March and a maximum daily frequency of 35.1 in June. The frequency curve had one significant peak in May through June and another significant peak in October through November. The monthly frequency of violence correlated with the absolute value of monthly change in length of day from the previous month. In the seven cities the highest monthly ratio of observed to expected frequencies increased with latitude. With increasing latitude, the months with the largest increase in violence came later both in the spring and in the fall. CONCLUSIONS: There is a distinct pattern of seasonal variation in the frequency of violence that varies systematically with latitude. This pattern resembles the seasonal pattern of some forms of suicide, hospitalization for affective disorders, and mood and activity in the general population.

Chi-Square Distribution↗
PubMed1990

The pattern of diarrhea in children in Khon Kaen, northeastern Thailand: I. The incidence and seasonal variation of diarrhea.

The incidence, seasonal variation and risk factors of diarrhea in children in Thailand are not well defined. The objective of this study is to identify the incidence and seasonal variation of diarrhea in a rural community. A cohort of 481 children under five years of age from 14 villages in rural northeastern Thailand was followed for 1 year, from May 1988 to April 1989. The data were collected daily by 5 participant observers who resided in the villages during the study period. During the 25,012 person weeks of surveillance, 384 episodes of diarrhea occurred; 279 episodes (72.7%) were watery diarrhea and 105 episodes (27.3%) were dysentery-like diarrhea. The incidence of diarrhea was 2.1, 1.76, 0.96 and 0.45 episodes per child per year for children aged 0-6 months, 7-12 months, 1 year and above 2 years, respectively. Males were affected as frequently as females. The average duration of illness was 4.9, 2.1, 1.5 and 0.5 days per child per year for children aged under 1 year, 1-2 years, 2-3 years and more than 3 years old, respectively. Both dysentery and watery diarrhea rates peaked for children of all ages from May to July, during the early rainy season. A second peak of watery diarrhea in the winter from November to January and was seen primarily in children less than 2 years old. The monthly incidence of diarrhea was associated with rainfall, ambient temperature and occupational behavior of people in each season.

Age Factors↗
PubMed1995

Seasonal variation in human reproduction: environmental factors.

Almost all human populations exhibit seasonal variation in births, owing mostly to seasonal variation in the frequency of conception. This review focuses on the degree to which environmental factors like nutrition, temperature and photoperiod contribute to these seasonal patterns by acting directly on the reproductive axis. The reproductive strategy of humans is basically that of the apes: Humans have the capacity to reproduce continuously, albeit slowly, unless inhibited by environmental influences. Two, and perhaps three, environmental factors probably act routinely as seasonal inhibitors in some human populations. First, it seems likely that ovulation is regulated seasonally in populations experiencing seasonal variation in food availability. More specifically, it seems likely that inadequate food intake or the increased energy expenditure required to obtain food, or both, can delay menarche, suppress the frequency of ovulation in the nonlactating adult, and prolong lactational amenorrhea in these populations on a seasonal basis. This action is most easily seen in tropical subsistence societies where food availability often varies greatly owing to seasonal variation in rainfall; hence births in these populations often correlate with rainfall. Second, it seems likely that seasonally high temperatures suppress spermatogenesis enough to influence the incidence of fertilization in hotter latitudes, but possibly only in males wearing clothing that diminishes scrotal cooling. Since most of our knowledge about this phenomenon comes from temperate latitudes, the sensitivity of spermatogenesis in both human and nonhuman primates to heat in the tropics needs further study. It is quite possible that high temperatures suppress ovulation and early embryo survival seasonally in some of these same populations. Since we know less than desired about the effect of heat stress on ovulation and early pregnancy in nonhuman mammals, and nothing at all about it in humans or any of the other primates, this is an important area for future research. Third, correlational data suggest that there may be some degree of regulation of reproduction by photoperiod in humans at middle to higher latitudes. Populations at these latitudes often show a peak in presumed conceptions associated with the vernal equinox. On the other hand, evidence gathered by neuroendocrinologists tends to argue against reproductive photoresponsiveness in humans.

Animals↗
PubMed2006

Effect of seasonal variation on the clinical course of chronic hepatitis B.

BACKGROUND: Seasonal variation in immunity has been found in healthy individuals and in association with some diseases. It is still unknown whether seasonal variation affects the clinical course of chronic hepatitis B. Our aim in this study was to explore the effect of seasonal variation on the clinical course of chronic hepatitis B. METHODS: The flare and remission time of chronic hepatitis B were observed in patients with hepatitis B virus (HBV) infection. All patients enrolled were followed up at least every 3 months for a mean follow-up time of 24.0 (range, 12-60) months. Seasonal decomposition was employed to analyze the relationship between seasonal variation and flares, remission, and hepatitis B e antigen (HBeAg) seroconversion in chronic hepatitis B patients during follow-up. RESULTS: A total of 2238 patients were observed in our study. Flare and HBeAg seroconversion were seldom seen in 1076 patients (48.08%) with alanine aminotransferase (ALT) levels of less than 2.0 x upper limit of normal (ULN) during follow-up (mean, 36 months). The remaining 1162 patients (51.92%) (766, HBeAg positive; 387 anti-HBeAg positive; 9 negative for both HBeAg and anti-HBeAg) with ALT levels >or=2.0 x ULN were followed longitudinally for 12 months to judge flare, remission, and HBeAg seroconversion. Flare, remission, and HBeAg seroconversion in patients with ALT levels >or=2.0 x ULN showed clear seasonal patterns (P < 0.001), with high peaks during spring, summer, and summer, respectively. An autocorrelation correlogram showed that flares, remission, and HBeAg seroconversion occurred with distinct periodicity in winter, spring, summer, and autumn. CONCLUSIONS: Seasonal variation might affect the clinical course of chronic hepatitis B. The role of seasonal triggering factors should be further investigated.

Adolescent↗