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PubMed2002

Seasonal variation in the incidence of aneurysmal subarachnoid hemorrhage in hospital- and community-based studies.

OBJECT: The aim of this study was to examine seasonal variations in the onset of aneurysmal subarachnoid hemorrhage (SAH) in one hospital-based and one community-based patient series. METHODS: The study population consisted of 941 patients with aneurysmal SAH who were admitted to Shimane Prefectural Central Hospital and 358 patients who were treated in Izumo City, Japan. When investigated as a whole, no significant seasonal variations were found in either population; however, in both series, statistically significant seasonal trends, with a peak in winter and a nadir in summer, were found among patients aged 59 years or younger (p < 0.05 for the hospital-based series and p < 0.005 for the community-based series), but not among those aged 60 years or older, regardless of sex. In the hospital-based series, seasonal variations were most apparent at certain times of day, with significant variations observed between 8:00 a.m. and 10:00 a.m. or 8:00 a.m. and noon (p < 0.001 and p < 0.005, respectively), regardless of patient age, and between 4:00 p.m. and 6:00 p.m. for patients aged 59 years or younger (p < 0.05). Consequently, seasonal variations were significant during daytime hours (between 8:00 a.m. and 8:00 p.m., p < 0.005) but not during the night (between 8:00 p.m. and 8:00 a.m.). Similar tendencies were found in the community-based series. Among patients aged 59 years or younger who had no risk factors for SAH, these seasonal variations were significant in both series. In patients with untreated hypertension, who were current smokers and daily alcohol drinkers, however, no significant patterns were observed in either series, even among younger patients. CONCLUSIONS: In both hospital- and community-based studies, aneurysmal SAH appears to undergo seasonal variation, with a peak in winter and a nadir in summer. This seasonal pattern may be derived mainly from the occurrence of SAH in the morning, but may also be modified by patient age and SAH risk factors, resulting in the masking of significant seasonal patterns when all patients are considered together.

Adult↗
PubMed1993

Seasonal variation in leisure time physical activity.

In this paper seasonal variation in leisure time physical activity for exercise is studied and quantified with regard to several popular exercise activities and taking the respondents gender, occupational status, and age into consideration. The analysis concerns data collected by telephone in Scotland between January 1989 and March 1992. Data from 7,202 male and 9,284 female respondents is used in the analysis; cosinor analysis using GLIM is applied. Considerable seasonal variation was found affecting both outdoor and indoor activities. During the peak phase in July, 32% of the respondents reported exercising for at least 20 min three or more times during the previous week, in the winter period this decreased to 23%. Older respondents were found to exercise more later in the year and also showed seasonal variation to a larger extent than younger respondents. This is particularly so for those respondents who exercise at a relatively high frequency.

Adolescent↗
PubMed2002

A study of weekly and seasonal variation of stroke onset.

A registry based study was conducted to assess the variation in first-onset stroke with weekdays and seasons, in relation to the effects of age. Between 1 December 1991 and 30 November 1998, 10,729 first-onset stroke patients aged 25 or more were registered in Toyama Prefecture, Japan. We compared the weekly and seasonal variation in first-onset stroke by a one-way goodness-of-fit chi(2)-test. The relationship between seasonal variation in stroke onset and age was also evaluated by the method of Kendall's tau-b R x C tables with ordered categories. The frequency of onset of all strokes and cerebral infarctions (CI) was significantly higher on weekdays than at weekends (P < 0.01). More men had strokes and CI on a Monday (P < 0.01), and more women had cerebral hemorrhage (CH) on a Monday and CI at the end of the week. Stroke incidence was higher in patients aged less than 60 years (20.6%) than in those aged 60 years or over (18.7%) on a Monday compared to the weekend. By chi(2)-test, comparing observed with expected numbers of stroke onsets, weighted by the number of days in each 3-month period, the incidence of all strokes, CI and CH was significantly higher in winter and spring than in summer. The seasonal variation in the onset of stroke declined with age: all strokes (P < 0.001) and CH (P < 0.001) in both genders; subarachnoid hemorrhage (P < 0.001) only in men. Our study shows that the onset of stroke is more frequent on weekdays than on weekends, and may be associated with changes in psychophysiological stresses between working days and the weekend. We also observed a clear negative dose response relationship between seasonal variations in occurrence and age. It may be speculated that younger people have more change to work outdoors, exposing themselves to the winter environment. Their lifestyle and physiological condition may be different from those of older people.

Adult↗
PubMed1988

Wind-chill and the seasonal variation of cerebrovascular disease.

The hospital admission rates for patients with specific types of stroke were examined for seasonal variation and correlation with meteorological factors. A seasonal variation in admission rates was found for subarachnoid haemorrhage, thrombo-embolic brain infarction and ill-defined cerebrovascular disease. Overall this seasonality was more strongly associated with the computed chilling effect of the atmosphere than with changes in temperature, humidity or wind speed alone. No seasonal variation was observed for admission rates of intracerebral haemorrhage, transient ischaemic attack or occlusion of precerebral arteries. Intracerebral haemorrhage admission rates exhibited a decrease with time. This evidence suggests that seasonal variation in admission rates exists only for certain pathological types of stroke and this is strongly associated with changes in the chilling effect of the atmosphere.

Adult↗
PubMed2004

Lack of seasonal variations in urinary calcium/creatinine ratio in school-age children.

Seasonal variations in urinary calcium excretion have been observed in adults and are thought to be due to seasonal changes in sunlight exposure, which results in fluctuation of blood levels of 25-hydroxyvitamin D. The goal of the present study was to explore the possible effect of season on urinary calcium/creatinine ratio (UCa/Cr) in healthy school children. We studied 65 healthy Caucasian children aged 5.1-14.6 years (mean+/-SD 9.6+/-2.0, median 9.7 years). Random, non-fasting urine samples were collected from each participant between the 1st and 5th days of the month for 16 successive months and analyzed for UCa/Cr. In parallel, meteorological data, which included average monthly temperature and average monthly UV index, were collected for the whole study period. A mathematical model describing the monthly mean values of UCa/Cr as a sine function was used to determine the presence of seasonal variation. The observed maximum mean UCa/Cr, 0.092 mg/mg (0.260 mmol/mmol), occurred in the late summer months (August/September) and minimum mean UCa/Cr, 0.083 mg/mg (0.235 mmol/mmol), occurred in mid-winter (January/February), reflecting an infinitesimal and statistically insignificant change. Moreover, both values were well within the previously established normal range for UCa/Cr of </=0.20 mg/mg (0.566 mmol/mmol). The pattern seen in the last 4 months of the study repeated that seen in the first 4 months. The mean temperature in July of the 1st year was 27.1+/-2.6, January 1.8+/-5.4, and July of the 2nd year 27.0+/-2.2 degrees C. The mean UV index in July of the 1st year (7.61+/-1.01) was not different from that in July of the 2nd year (7.73+/-0.86), and both were statistically much higher than that in January (1.37+/-0.44) ( P<0.001). Evidently, in spite of significant changes in seasonal meteorological indices of sunlight, no significant seasonal variations in UCa/Cr were observed in a cohort of healthy school children. Thus the current UCa/Cr value used to diagnose hypercalciuria does not require a seasonal adjustment.

Adolescent↗
PubMed1996

Sarcoidosis causes abnormal seasonal variation in 1,25-dihydroxy-cholecalciferol.

OBJECTIVES: The spontaneous seasonal variations in the calcium regulating hormones 1,25-dihydroxy-cholecalciferol (1,25-DHCC) and parathyroid hormone (PTH) were investigated in patients with sarcoidosis. DESIGN: Controlled, prospective observational study with measurements in the winter and summer seasons, respectively. SUBJECTS: Twelve patients (age: median 33, range 21-54 years) with biopsy-verified (n = 8) sarcoidosis were included as well as 11 age-matched healthy control subjects. MAIN OUTCOME MEASURES: Serum values of calcium, ionized calcium, phosphate, chloride, bicarbonate, creatinine, albumin, angiotensin-converting enzyme, alkaline phosphatase, 1,25-DHCC, and PTH. Also, 24-h whole body retention of 99mTc methylene-diphosphonate was assessed. RESULTS: The patient group showed an increased level of 1,25-DHCC in the summer season (w:146 +/- 67, s:198 +/- 73 pmol L-1; P < 0.01) in contrast to the opposite finding among controls (w:161 +/- 34, s:144 +/- 43 pmol L-1; P < 0.05). Comparing the individual seasonal changes between the two groups, the difference was marked (P < 0.001). Compared with controls, total serum calcium was elevated in the summer season in the patient group (P < 0.05), in which the same parameter correlated positively with 1,25-DHCC (r = 0.658; P < 0.01). PTH was increased two to three times above the control values throughout the year (patients: w:0.37 +/- 0.13, s:0.24 +/- 0.08 micrograms L-1; controls: w:0.14 +/- 0.09, s:0.10 +/- 0.04 micrograms L-1; P < 0.001); although, the level of this hormone was still found within the reference interval. 24-h whole body bone scintigraphy failed to show any seasonal variation in bone metabolism. In contrast, serum alkaline phosphatase was found to be increased during the summer season compared with the control group (P < 0.001). Angiotensin-converting enzyme showed no seasonal variation. CONCLUSIONS: In sarcoidosis, 1,25-DHCC is abnormally regulated throughout the year, with a significantly higher serum level in the summer season. Uncontrolled production of 1,25-DHCC in sarcoid pulmonary alveolary macrophages is possibly responsible for hypercalcaemic episodes, and this parameter should be used as a marker of disease activity.

Adult↗
PubMed1999

Weekly and seasonal variation in the incidence of cardiac arrests.

BACKGROUND: Patterns of temporal variation of cardiac arrests may be important for understanding mechanisms leading to the onset of acute cardiovascular disorders. Previous studies have reported diurnal variation of the onset of cardiac arrests, with high incidence in the morning and in the evening, lack of daily variation during the week, and some seasonal variation. METHODS AND RESULTS: We explored weekly and yearly (seasonal) temporal variation in 6603 out-of-hospital cardiac arrests attended by the Seattle Fire Department. We observed daily variation that peaks on Monday and seasonal variation that peaks in the winter. CONCLUSIONS: Cardiac arrests do not occur randomly during the week or year but follow certain periodic patterns. These patterns are probably associated with patterns of activities.

Adolescent↗
PubMed2000

Seasonal variation of hip fracture at three latitudes.

We studied the seasonal variation of hip fracture admissions at three different latitudes: Scotland (56 degrees North; 54,399 admissions); Shatin, Hong Kong (22 degrees North; 4180 admissions); and Auckland, New Zealand (36 degrees South; 2257 admissions). We calculated the extent of seasonal variation (amplitude) and the time of year of the peak value (acrophase) by fitting a sine curve to monthly data using cosinor analysis. A significant seasonal variation was found in all three countries, at a high level in Scotland (p < 0.01) and Hong Kong (p < 0.001), but just significant in New Zealand (p < 0.05). The extent of the seasonal change was very similar in Scotland and New Zealand, but, as expected, the peak in New Zealand (early September) was approximately six months ahead of Scotland (mid February). In Hong Kong, the amplitude was three times greater than in Scotland and the peak occurred a month earlier. There is neither snow nor ice in Hong Kong, and this provides powerful evidence against a major influence of conditions underfoot causing extra falls in winter. In Scotland there was a significant increase in the proportion of deaths in winter as compared to summer. The Scotland/Hong Kong amplitude difference is striking, but it is unknown whether this has a genetic or environmental explanation. The cause of seasonal death difference to a given injury is also unknown. Possible mechanisms are discussed, but the purpose is to report two new epidemiological features, without wild speculative hypotheses. The findings should be viewed as leads to further epidemiological, clinical and more basic research.

Female↗
PubMed1981

Seasonal variation of aryl hydrocarbon hydroxylase activity in human lymphocytes.

A seasonal variation was observed when aryl hydrocarbon hydroxylase (AHH) activity was measured in the cultured lymphocytes of 977 donors over a period of 2 1/2 years. The variation was strongest in AHH activity induced by 3-methylcholanthrene and was less apparent for AHH activity in lymphocytes grown without any inducer. The period of the seasonal variation is 1 year, and maximal induced AHH activity occurs during late summer and early fall with minimal activity 6 months later. Based on the average of all individuals tested during the highest and lowest weeks, induced AHH activity can be as much as 10-fold higher during the peak season. It is not possible to tell from these experiments whether the seasonal variation is tissue specific, occurring only in lymphocytes, or characteristic of microsomal oxidases in other tissues as well.

Adolescent↗
PubMed2006

Seasonal variations of acute massive submacular haemorrhage associated with age-related macular degeneration.

AIMS: To determine whether there is a seasonal variation in the onset of acute, massive submacular haemorrhage associated with age-related macular degeneration. METHODS: Sixty eyes of 59 patients diagnosed between April 1998 and March 2005, were studied retrospectively. For each patient, the month and season of onset of the submacular haemorrhage and the mean monthly ambient temperature in Nagoya were analysed. Any history of systemic hypertension was also recorded, and the seasonal variations were also investigated in hypertensive and non-hypertensive groups. RESULTS: The number of cases peaked in winter with a trough in summer, and this seasonal variation was significant (Roger's R = 12.03, p<0.01). The monthly incidence was inversely correlated with the temperature (Spearman's rank correlation coefficient r = 0.89, p<0.01). The seasonal variations were significant in the hypertensive group but not in the non-hypertensive group. CONCLUSION: The considerable seasonal variations suggests that the mechanism for the haemorrhage is strongly correlated with the systemic blood pressure.

Acute Disease↗
PubMed1995

Geographic differences in seasonal variation of mean birth weight in Japan.

Seasonal variation of mean birth weight (MBW), mean gestational period (MGP), and MBW at 40 weeks of gestation (MBW40) in the 15 different prefectures of Japan were analyzed using vital statistics from 1974 to 1983. MBW generally shows a bimodal pattern with two peaks in spring and autumn and two troughs in summer and winter. Seasonality exhibits a general geographic trend: The autumn peak loses its height and the spring peak increases its amplitude as one moves from north to south. This trend suggests that environmental factors are associated with the creation of seasonality in MBW. For MGP the pattern is relatively unimodal with a deep trough in winter; however, a late summer small dip is observed in most cases. According to an analysis of coincidence between the two time series (MBW and MGP) and correlation analysis, the seasonal variation in birth weight basically depends on the gestational period. For MBW40, which represents the fetal growth rate, the seasonality shows a pattern similar to that of MBW. A statistically significant coincidence and a correlation are observed between the time series of MBW and MBW40. These results suggest that the two processes of fetal growth (gestational period and fetal growth rate) are associated with the creation of seasonality in MBW.

Birth Weight↗
PubMed1993

Seasonal variation in high density lipoprotein cholesterol.

We investigated the seasonal variation in high density lipoprotein cholesterol (HDL) in 142 dyslipidemic (non-HDL-cholesterol > or = 5.2 mmol/l) middle-aged men in the placebo group of the Helsinki Heart Study over the 5-year trial period. A seasonal pattern was found in HDL fluctuation, with a 4.5% drop during mid-winter (5-year mean 1.192 +/- 0.265 mmol/l) compared with a stable level (5-year mean 1.248 +/- 0.281 mmol/l) during the rest of the year (P < 0.001). A less pronounced seasonal variation in HDL was observed in 85 subjects receiving gemfibrozil. Although affecting pretrial HDL level in cross-sectional analyses, age, alcohol consumption, dietary adherence, physical activity and serum triglycerides had no influence on the seasonality of HDL variation. Smoking had a slight attenuating effect on the variation pattern. Pretrial HDL was influenced by relative weight, but there was also an inverse relationship between HDL and body weight variations, i.e. the annual drop in HDL coincided with the annual peak in body weight. However, seasonal HDL variation was not directly reflected in the annual variation in CHD incidence.

Adult↗
PubMed2003

Seasonal variation in insulin sensitivity in healthy elderly people.

OBJECTIVE: There is a seasonal variation in the incidence of diabetes mellitus and cardiovascular diseases. However, there is very little information about the seasonal variation in insulin sensitivity. We report the seasonal variation in insulin sensitivity in a group of elderly subjects followed for 1 y. METHODS: Healthy elderly (>/=70 y) subjects living independently were included. Fifty percent of subjects received a daily nutritional supplement that provided 400 kcal, 15 g of protein, and 50% of vitamin daily reference values (DRVs). Those receiving and not receiving supplements were randomly assigned to a resistance exercise training program. Every 6 mo (winter, summer, and winter), body composition was measured by dual-energy x-ray absorptiometry and blood samples were used to measure serum lipids, fasting and postprandial glucose, and insulin levels. RESULTS: One hundred eight subjects (31 supplemented and trained, 28 supplemented, 16 trained, and 33 without supplementation or training) completed the follow up. Higher homeostasis assessment of insulin sensitivity, postprandial insulin, and fasting triacylglycerol levels were observed during the summer than during the winter. Body fat increased steadily during the study period, and fat-free mass did not change. Serum low-density lipoprotein cholesterol decreased significantly in the supplemented and trained group and increased in the non-intervention group. CONCLUSIONS: In this group of elderly subjects, insulin resistance and triacylglycerol levels were higher during the summer. Nutritional supplementation and training had a positive effect on serum low-density lipoprotein cholesterol.

Absorptiometry, Photon↗
PubMed1988

Lack of seasonal variation in bone mass and biochemical estimates of bone turnover.

Three previous studies have indicated a seasonal variation in bone mineral content, with values during the summer being 1.7% to 7.5% higher than during the winter. We have examined the seasonal influence on both bone mass, biochemical estimates of bone turnover and vitamin D metabolites in 86 healthy women, aged 29-53 years. All participants were followed up for 2 years with examinations every 6 weeks or 3 months. Bone mineral content in the proximal and distal part of the forearm (single photon absorptiometry) did not reveal any significant seasonal variation, whereas bone mineral density of the lumbar spine (dual photon absorptiometry) indicated that the highest values occurred in winter. None of the biochemical parameters showed any statistically significant cyclical changes. Serum concentrations of 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D3 showed a highly significant seasonal variation, whereas the serum 1,25-dihydroxyvitamin D concentration was virtually unchanged. We conclude that seasonal variation in bone mineral content and bone turnover should not be taken into account when interpreting data from longitudinal studies of healthy pre- and postmenopausal women on a sufficient vitamin D nutriture.

Adult↗
PubMed2004

Estimation of seasonal variations in risk factor profiles and mortality from coronary heart disease.

OBJECTIVE: Seasonal variations in coronary heart disease (CHD) and related risk factors have been reported previously. However, no studies to date quantify the contribution of seasonal variations in risk factors to actual mortality in both men and women using a single database of sufficient size and follow-up. METHODS: We investigated the database from the Western Austrian Vorarlberg Health Monitoring and Promotion Programme (VHM&PP) including over 450,000 repeated measurements of 149,650 individuals between 1985 and 1999. RESULTS: Of a total of 1266 deaths from CHD (ICD-9 410-414), 353 deaths occurred between December and February (27.9%), in contrast to 275 (21.7%) between June and August. While the frequency of deaths through acute myocardial infarction (ICD-9 410) was similar over the seasons, chronic forms of CHD (ICD-9 414) occurred significantly (p < 0.001) more frequently in winter. Total cholesterol, blood pressure and body mass index showed pronounced seasonal variations with average levels significantly higher during the winter months in all age groups and both sexes, giving an estimated increase in score risk of 6.8% in men and 3.6% in women. However by contrast, use of single time point risk factor data tended to over-estimate subsequent 10 year mortality if measured in winter and the converse in summer. CONCLUSION: For the first time, this study quantifies the contribution of seasonal risk factor variation to CHD mortality. The consistent effect across demographic groups suggests that this is a real physiological phenomenon and not an artefact of living conditions. Interpretation of standard risk scores should take account of this seasonal fluctuation in subsequent investigation and follow-up.

Adult↗
PubMed1984

Circannual versus seasonal variations of longitudinally sampled 25-hydroxycholecalciferol serum levels.

Seasonal variations in human serum levels of 25-hydroxycholecalciferol (25OHD) have been largely documented in transverse studies of population. But seasonality is not per se a demonstration that 25OHD serum levels fluctuate along the course of year according to a waveform profile with a periodic rhythm. Because of this, we attempted to investigate the possible occurrence of a circannual rhythm for 25OHD serum levels in a longitudinal design, by fitting a 365.25-day cosine curve to temporal biodata recorded in 10 clinically healthy subjects, monthly sampled for RIA determinations of 25OHD. Cosinor procedure statistically validated the occurrence of a circannual rhythm for 25OHD serum concentrations at a highly significant level of probability (P = 0.0015) for null hypothesis amplitude = 0. With 95% of probability, amplitude ranges from 5.0 to 16.5 ng/ml (mean value of oscillation = 10 ng/ml), while acrophase is temporally located from September 14 to December 3 (mean timing = October 21). Yearly, mean values for 25OHD serum concentrations is of 40.3 +/- 5.4 ng/ml as quantified by the line which transversely divides the cosine curve interpolating original biodata. By calculating the band of a complete 12 months variability which includes 90% of the distribution with 90% confidence limits, the circannual chronodesm of 25OHD serum levels has been obtained. Such a chronodesmic sinusoid has been compared to the circannual chronogram. By this comparison, a dissociation between the crest (October) and the peak (August) has been detected. The finding suggests that seasonal variations are superimposed to the circannual rhythm. Seasonal but also circannual changes, thus, characterize the yearly variability of 25OHD serum levels in man.

Adult↗
PubMed1993

[Seasonal variation of sudden death based on analysis of death certificate information].

Seasonal variation of sudden death (SD) was studied based on analysis of death certificates of all 8,519 SD patients, aged 15 years or older, who died during 1984 to 1986 in Niigata prefecture, Japan. SD was defined as death within 24 hours of onset of the underlying cause. SD showed a significantly high incidence during the cold season. When analyzed by underlying cause, the high incidence during cold season was shown for SD by circulatory diseases such as acute myocardial infarction (AMI; n = 1,446), other cardiovascular diseases (OCD; n = 4,375) and cerebrovascular accident (CVA; n = 1,725). However, no significant seasonal variation was observed for SD by non-circulatory diseases. By age group, the incidence of SD due to circulatory diseases was high during the cold season in the elderly (61 to 75 years) and the old age (76 years or older) groups, irrespective of kinds of the diseases, whereas the pattern varied by disease type in the young to middle age group (15 to 60 years). The highest incidence of SD due to AMI in the young to middle age group occurred in January with a second peak in July to August. Thus, not only low temperatures but high temperatures seemed to also contribute to the occurrence of SD by AMI in this age group. While SD due to OCD in this age group did not show a significant seasonal variation, that due to CVA showed a high incidence during cold season similar to the older age groups. These results suggest that factors affecting the occurrence of SD differed according to underlying cause and age of victims.

Age Factors↗