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 55 records · Page 3Linked to original sources
PubMed2000

Seasonal variation of livebirths, stillbirths, extramarital births and twin maternities in Switzerland.

A study was made of the seasonal variation in all births, and births according to marital status, multiplicity and birth status (live and still) in Switzerland recorded between 1876 and 1990. To obtain seasonal variation in as pure as possible form, our analyses are based on rates. When comparing the seasonality in data sets showing markedly different levels, standardised indices were used. Assuming the length of pregnancies with twins to be about one month shorter than for pregnancies with singletons, lagged twinning rates were calculated but, in comparison with actual twinning rates, the general seasonal variation remained. Therefore, this study was based on actual twinning rates. A monotonic increase in the amplitude of the seasonal variation in general births was noted for the period 1876-1930, with strong seasonal variation holding for 1921-1980. After that, a marked decline in the amplitude can be observed. Seasonality of both all births and twin maternities showed very similar pattern for the periods 1876-1930 and 1969-1990, with maxima in the spring (March-May) and troughs in late autumn (October-December). Twin maternities showed a strong seasonality for the period 1876-1930, being about 20% higher in March than in October. The twinning rate in the period 1876-1930 was about 2.6 per thousand units higher than in the period 1969-90. For twin maternities there was also a stronger seasonal variation during the earlier period than during the later one. The pattern of the seasonal variation for extramarital births, showing a maximum in February (conceptions in May-June) and a minimum in August (conceptions in November-December) with a difference of no less than 24% was more marked than for the marital births. It seems likely that this seasonality of extra-marital maternities was due mainly to seasonal variation of coital rates and multiple ovulation in the early summer months coinciding with optima of light, temperature and food supply. A strong reduction in the rate of stillbirths (gestational age more than 29 weeks) was observed during the twentieth century. The stillbirth rate declined from about 40 per 1000 in the 1870s to fewer than 5 per 1000 in the 1980s. Irrespective of this strong decline in the stillbirth rate, the same seasonal rhythm was noticed throughout the period with high stillbirth rates among births around March and low rates during the summer and autumn.

Abortion, Spontaneous↗
PubMed2004

A comparison of seasonal variation between suicide deaths and attempts in Hong Kong SAR.

BACKGROUND: Seasonal variations in suicide deaths and attempted suicides have been reported for many countries. Recent research has suggested that seasonal patterns of suicide deaths have diminished considerably. The seasonality pattern between attempts and completed ones are not the same. This paper is the first one to examine seasonal variation between suicide deaths and attempts simultaneously. METHOD: Census and Statistics Department and the Hospital Authority provided mortality and morbidity data on suicides for the period 1997-2001 in Hong Kong SAR, respectively. Seasonal patterns of suicide deaths and attempts were examined by a harmonic analysis and a non-parametric chi-square test. RESULTS: A significant seasonal variation was detected in suicide attempts with a markedly bi-seasonal pattern was found amongst females with a peak in May and October; only a cyclic pattern was observed for males with a peak in summer. The female attempters who used non-violent suicide methods contributed to the second peak in October. On the other hand, there was no evidence of significant differences in the seasonal distribution among the suicide deaths for males and females. Only a mild pattern was found amongst females involving in violent suicide deaths, while others can be treated as a random event and no significantly pattern was observed in our study. Overall, a significant difference in seasonal variation existed between suicide deaths and attempts (p-value<0.01). CONCLUSIONS: This study reinforces the findings that seasonal variation in suicide appears to be diminishing. Also, suicide attempters and completed suicides in Hong Kong seem to arise from two non-identical but overlapping groups in the community.

Adult↗
PubMed1979

[Seasonal variations of a forest soil microflora (author's transl)].

Variations between seasonal samplings of a forest soil were studied during a one year cycle. The total number of microorganisms was maximal in march, while qualitative variations of the bacterial and fungal flora were unimportant. Electron microscope studies showed physiological differences and enabled to evaluate the seasonal variations of the type of associations of soil microbes.

Bacteria↗
PubMed2004

Could seasonal variation in testosterone levels in men be related to sleep?

We have previously reported seasonal variations in both total and free testosterone in men living in north Norway. The aim of this cross-sectional study was to determine whether seasonal variation in testosterone also occurs in men living in geographical areas with less extreme seasonal variation in sunlight and temperature. In 915 men aged 24-91 years from Rancho Bernardo, a suburb of San Diego in southern California, we found that neither total nor bioavailable testosterone varied by season, with or without adjustments for age and anthropometric measurements. Of all examined covariates, only physical activity showed a seasonal variation, with a peak in August (p < 0.001), and adjusting for physical activity did not change the lack of seasonal variation in testosterone. In addition, there was no association between testosterone and mean air temperature, or testosterone and possible hours of sunshine. We conclude that men living in southern California show no seasonal variation in testosterone levels. One possible explanation, besides the difference in climate, for the diverging findings between our previous study and the present study is different sleep patterns.

Adult↗
PubMed1992

[Seasonal variation of mean birth weight and births in Nagano Prefecture].

Seasonal variation of mean birth weight in Nagano Prefecture was examined by a traditional time series analysis, which decomposes the variation in a series into trend, seasonal variation, 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 unimodal pattern with a peak in June for males, and a bimodal pattern with peaks in spring and autumn in females with statistical significance. Previous reports have revealed that gestational period is the most important factor associated with birth weight. Therefore, we carried out time series analysis for the mean gestational period and observed an apparent seasonal periodicity, which showed a unimodal pattern with a bottom in winter for both sexes and parities. According to the results of statistical testing of the degree of coincidence between two time series, the time series of mean birth weight and that of mean gestational periods showed statistically significant coincidences in their monthly variations for multiparae. On the other hand, mean birth weight at 40 gestational weeks, which reflects the intrauterine growth, did not show seasonality. These results suggest that seasonality in gestational periods might play an important role in creating seasonal variations of mean birth weight in Nagano Prefecture. The average daily number of births by month also showed apparent seasonalities both for primiparae and multiparae. Primiparae showed a bimodal pattern with peaks in February and August, while multiparae showed a unimodal pattern with a peak in May and a bottom in November. It has been said that the seasonality in marriage is one of important factors associated with seasonal variation in births.(ABSTRACT TRUNCATED AT 250 WORDS)

Birth Rate↗
PubMed2006

Seasonal variation in mortality from myocardial infarction and haemopericardium. A postmortem study.

BACKGROUND: Seasonal variation in the incidence of and mortality from myocardial infarction (MI) has been well recognised for many years. Haemopericardium (HP) is usually a fatal complication of MI. No data exist in the literature with regard to the seasonal variation in mortality from HP. AIMS: To perform a necropsy based study to confirm seasonal variation in mortality from MI in a London population and to determine whether seasonal variation in mortality from HP can be established. METHODS: Postmortem causes of death issued by several pathologists, working in two public London mortuaries over a five year period from 1999 to 2004 were analysed. Deaths caused by HP secondary to traumatic or iatrogenic causes were specifically excluded, as were deaths caused by HP secondary to bicuspid aortic valve and aortic dissection. The results were subdivided into winter (1 November to 31 March) and summer (1 April to 31 October). RESULTS: In total, there were 2266 cases of MI and 135 cases of HP. Significantly more deaths from HP (83 of 135; 61.5%; p = 0.004) and MI (1051 of 2266; 46.4%; p = 0.016) occurred in the five month winter period. Furthermore, there was a significantly higher incidence of HP compared with MI during the winter (83/1051; 7.9%) than the summer (52/1215; 4.3%; p<0.001). There was no significant difference in the age or sex of patients dying in either the winter or summer. CONCLUSION: There is seasonal variation in mortality from both MI and HP in the London population, as confirmed by a postmortem study.

Age Factors↗
PubMed1983

Seasonal variations of total histamine in patients with seasonal allergic rhinitis.

Seasonal variations of total blood histamine were examined in twenty patients with seasonal allergic rhinitis (Japanese cedar pollinosis). In blood specimens taken in the pollen season of 1978, the symptom-free season of 1978, and the pollen season of 1979, the mean values of blood histamine were 61.6, 50.0 and 84.2 ng/ml respectively. The differences in blood histamine levels between the pollen season of 1978 and the symptom-free season of 1978 and between the symptom-free season of 1978 and the pollen season of 1979 were statistically significant. In the symptom-free season of 1978, the blood histamine levels of twenty normal subjects were also examined; the mean value was 58.2 ng/ml. The blood histamine levels of the patients in the symptom-free season were not statistically different from those of the normal subjects.

Adult↗
PubMed2006

Seasonal variation of estradiol, follicle stimulating hormone, and dehydroepiandrosterone sulfate in women and men.

CONTEXT: Seasonal variation in daylight regulates reproduction in animals living at higher latitude, but the influence of season on the sex hormones in humans remains unclear. OBJECTIVE, DESIGN, AND PARTICIPANTS: A cross-sectional population-based study in Tromsø, Norway (70 degrees N) included 1651 women and 1540 men aged 25-84 yr. Circulating total estradiol (and calculated free levels), FSH, and dehydroepiandrosterone sulfate (DHEAS) were measured between September 1994 and September 1995 and provided a unique opportunity to study effects of extreme seasonal variations in the daylight on hormone levels in an arctic population. MAIN OUTCOME MEASURE: Circulating total and free estradiol, FSH, and DHEAS were measured. RESULTS: Total and free estradiol showed differences between monthly means, with peak in June in postmenopausal women (P < 0.001), and in May in men (P = 0.002 and P < 0.001) by analysis of covariance. By cosinor analysis, a seasonal variation in total and free estradiol was evident in women (P = 0.02 and P = 0.03) and men (P = 0.004 and P = 0.001), but only 0.2-0.9% of the variation in total and free estradiol was explained by season. FSH and DHEAS showed no obvious seasonal variation in either sex. CONCLUSIONS: Seasonal variations should be considered while designing studies and interpreting results of estradiol measurements to avoid bias in comparative studies.

Adult↗
PubMed1998

Absence of seasonal variation in the phase of the endogenous circadian rhythm in humans.

Humans may be subject to seasonal variations, as evidenced by the existence of seasonal affective disorder (SAD) and midwinter insomnia. However, some recent studies have shown that the seasonal variation in the phase of the circadian rhythm is relatively weak in healthy humans. In the present study, evidence is found that there is no seasonal variation in the phase of the endogenous circadian rhythm at all. Body temperature, cortisol excretion, and subjective alertness of six subjects recorded under constant routine conditions showed no systematic seasonal variation in circadian phases. This finding indicates that secondary zeitgebers blocked or counterbalanced the seasonal variation in the entrainment effect of the natural photoperiod. The human being may live in an environment in which the photoperiod has lost its status of primary zeitgeber.

Adolescent↗
PubMed2006

Seasonal variation in the diagnosis of type 1 diabetes in south-east Sweden.

With the aim to survey the seasonal pattern of diagnosis of type 1 diabetes we included all 1903 children <16 years of age and who had been diagnosed with type 1 diabetes between 1977 and 2001 in the south-east of Sweden. To investigate the seasonal pattern a mixture of two cosine functions was included in a logistic regression model. There was a clear seasonal variation over the years (p<0.001). Children in the oldest age group (11-15 years) showed the most obvious seasonal variation (p<0.001). Children with a short duration of symptoms had about the same seasonal variation as children with a long duration. Both children with and without an infection 3 months prior to diagnosis showed significant seasonal variation (p<0.001) although the seasonal pattern differed between the two groups (p<0.001). As the incidence of diabetes increased during the 25 years the study period was divided into periods of 5 years and it was only during the two last periods that significant seasonal variation occurred. There is a clear seasonal variation in diagnosis of type 1 diagnosis in children and the results suggest that children with a less aggressive disease process at diagnosis were most responsible for this variation. Children with and without prior infection showed a different seasonal pattern.

Adolescent↗
PubMed1993

Seasonal variation of serum lipids in an elderly population.

We investigated seasonal variation in serum lipids in 96 volunteers aged 65-74 years who were studied at 2-monthly intervals for one year. Periodic regression analysis revealed highly significant seasonal variation in serum total cholesterol and high-density lipoprotein (HDL) cholesterol. Peak levels for both occurred in winter with corresponding summer troughs. The seasonal difference for total cholesterol was 0.32 mmol/l (95% CI 0.23-0.41, p < 0.0001) and that for HDL cholesterol 0.16 mmol/l (95% CI 0.12-0.19, p < 0.0001). Low-density lipoprotein (LDL) cholesterol was highest in winter in men only (seasonal difference 0.27 mmol/l, 95% CI 0.15-0.39, p < 0.0001), and triglycerides were significantly greater in late winter for women only (seasonal difference 0.22 mmol/l, 95% CI 0.09-0.35, p = 0.002). The timing of seasonal variation in total cholesterol and triglycerides would be consistent with a role in the seasonal variation in vascular deaths, but our finding of a relatively high HDL: total cholesterol ratio in winter makes this less likely.

Aged↗
PubMed1994

Seasonal variation of neonatal and infant deaths by cause in Greece.

The seasonal variation of neonatal and infant deaths in Greece was analyzed for nine consecutive years (1979-1987) by cause of death, age of death and urbanization of permanent residence. Data were supplied by the National Statistical Service of Greece. Statistical analysis was done using the Edward's method. The seasonal patterns of the number of deaths and death rates were similar. Neonatal deaths in total did not show significant seasonality but postneonatal deaths showed seasonal variation with a peak in the winter, more evident in rural areas. Neonatal deaths from prematurity showed statistically significant seasonal variation with a peak in May. Postneonatal deaths from infections and mainly those from pneumonia showed very significant seasonal variation with a peak in February that was more prominent in rural areas. Seasonal pattern with peak in late winter was also found for postneonatal deaths from injuries. The seasonal patterns for neonatal and postneonatal deaths from sudden infant death syndrome were suggestive of an increased occurrence during the winter months mainly in urban areas.

Age Factors↗
PubMed1998

Seasonal variations in office and home blood pressures in hypertensive patients treated with antihypertensive drugs.

OBJECTIVE: To analyze various factors influencing season variations in blood pressure under ordinary circumstances. METHODS: We examined home and office blood pressures in 315 outpatients with essential hypertension. The majority (88%) were being administered antihypertensived drugs. Their office and home blood pressures were recorded in 1993. The patients were 156 men and 159 women, aged 60.8 +/- 0.6 years (mean +/- SEM). The office blood pressure was measured monthly by the same physicians. The home blood pressure was measured every day by the patients, in the morning and evening. RESULTS: The home blood pressures both in men and in women exhibited significant seasonal variations, to a similar extent. The winter-summer difference in home blood pressure was 3.9 +/- 0.5 mmHg systolic and 1.7 +/- 0.3 mmHg diastolic for the men and 4.6 +/-0.5 mmHg systolic and 2.4 +/- 0.3 mmHg diastolic for the women. The office blood pressure of the men also exhibited significant seasonal variation. There was no seasonal variation in office systolic blood pressure in the women. The levels of home blood pressure in the men and women were similar during each season, whereas the office systolic blood pressure of the women was significantly higher than that of men throughout the year. For the total group of patients, the winter-summer differences in home systolic blood pressure was positively correlated to age. The seasonal variations in blood pressure were not affected by body mass index, smoking status, and administration of antihypertensive medication.CONCLUSIONS: Seasonal variations in blood pressure existed both for male and for female hypertensive patients and occurred even for subjects being treated with antihypertensive drugs. However, there was no seasonal variation in the office systolic blood pressure of women, suggesting that the differences between the office and home blood pressures and between thermoregulatory mechanisms for the sexes may have obscured it.

Journal Article↗
PubMed1997

Seasonal variation in the occurrence of homicide in Finland.

OBJECTIVE: Although seasonal variation in impulsive aggression related to circannual rhythms of central serotonin neurotransmission is a topic of current interest, there is little firm knowledge on seasonality in the occurrence of homicide. Longitudinal studies on the seasonal rhythms of platelet imipramine binding and L-tryptophan levels have placed the circannual peaks around January and February and the nadirs around May and August. The aim of this study was to test the hypothesis that the number of homicides is the lowest during winter and the highest during spring and summer. A secondary hypothesis was that the seasonal variations in homicides and violent suicides are correlated. METHOD: The largest database on the monthly occurrence of homicide thus far (N = 4,553) was used in this study, in which the monthly occurrence of all murders and manslaughters in Finland during the years 1957-1995 was analyzed. RESULTS: During winter the homicide rate was 6% below the expected rate. Correspondingly, during summer there was a 6% elevation above the expected homicide rate, but no significant peak was observed in spring. There was a significant association between the monthly occurrence of homicides and violent suicides but not between homicides and nonviolent suicides. CONCLUSIONS: The results suggest that a seasonal variation in the occurrence of homicide exists. On the basis of current literature, it could be hypothesized that this seasonal variation and the correlation between the monthly occurrence of homicides and violent suicides are associated with the observed circannual rhythms of serotonin transmission.

Biomarkers↗
PubMed1954

Epidemicity of poliomyelitis; possible role of seasonal variation in food quality.

Seasonal variations occur in the phosphate, phospholipid and protein content of foods. The lower content occurs in the dry season. This is most often in the summer and fall months, which is the usual time of year for epidemics of poliomyelitis. Question is raised as to whether epidemics of poliomyelitis are a consequence of the host-virus balance being shifted in favor of the virus during this season because of the lower nourishing power of foods common to the daily diet.

Diet↗
PubMed1995

Seasonal variation in coronary heart disease in Scotland.

STUDY OBJECTIVE: Seasonality of coronary heart disease (CHD) was examined to determine whether fatal and non-fatal disease have the same annual rhythm. DESIGN: Time series analysis was carried out on retrospective data over a 10 year period and analysed by age groups ( < 45 to > 75 years) and gender. SETTING: Data by month were obtained for the years 1962-71. The Registrar General provided information on deaths and the Research and Intelligence Unit of the Scottish Home and Health Department on hospital admissions. SUBJECTS: In Scotland, between 1962 and 1971, 123 000 patients were admitted to hospital for CHD, of whom 29 000 died. There were a further 97 000 CHD deaths outside hospital. These two groups were also examined as one (coronary incidence) - that is, all coronary deaths and coronary admissions discharged alive. STATISTICAL ANALYSIS AND MAIN RESULTS: Where there was a single annual peak, the sine curve was analysed by cosinor analysis. When there were two peaks the analysis was by normal approximation to Poisson distribution. In younger men (under 45 years) admitted to hospital there was a dominant spring peak and an autumn trough. A bimodal pattern of spring and winter peaks was evident for hospital admissions in older male age groups: with increasing age the spring peak diminished and the winter peak increased. In contrast, female hospital admissions showed a dominant winter/summer pattern of seasonal variation. In male and female CHD deaths seasonal variation showed a dominant pattern of winter peaks and summer troughs, with the winter peak spreading into spring in the two youngest male age groups. CHD incidence in women showed a winter/summer rhythm, but in men the spring peak was dominant up to the age of 55. CONCLUSION: The male, age related spring peak in CHD hospital admissions suggests there is an androgenic risk factor for myocardial infarction operating through an unknown effector mechanism. As age advances and reproduction becomes less important, the well defined winter/summer pattern of seasonal variation of CHD is superimposed, and shows a close relationship with the environment, especially temperature, or the autumn and early winter fall in temperature.

Adult↗
PubMed1992

Seasonal variations in the onset of retinal vein occlusion.

Seasonal variation in the development of retinal vein occlusion in 1003 consecutive patients with various types of retinal vein occlusion was studied prospectively from 1973 to 1990. No seasonal variation in the onset of any type or combination of types of retinal vein occlusion was found. This refutes previous reports of such seasonal variation, which were based on small retrospective series.

Adult↗
PubMedDate not supplied

Seasonal variation of blood pressure in maintenance hemodialysis.

CONTEXT: 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. OBJECTIVE: To investigate the seasonal variation of blood pressure in Brazil, a tropical country, in patients on hemodialysis. DESIGN: Prospective, cohort study. SETTING: Dialysis unit of a tertiary medical center (a teaching hospital of the University of São Paulo School of Medicine, São Paulo). PATIENTS: Sixteen patients with chronic renal failure undergoing hemodialysis. OUTCOMES: Blood pressure, body weight, and ambient temperature were evaluated during 6 hemodialysis sessions carried out on 13 days during the four seasons. RESULTS: 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). CONCLUSIONS: 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.

Adult↗