Seasonal Variation In Incidence Research Articles

Epidemiology of biliary atresia in France: a national study 1986–96

Background/Aims: The reported incidence of biliary atresia varies from 5 to 32/100 000 live births. The existence of seasonality and/or clustering is controversial. Based on a large population analysis, we examined the incidence of biliary atresia in France, and the space-time distribution of cases. Methods: All patients with biliary atresia living in France and born in the years 1986–96 were recorded. Geographic distribution, seasonality, time clustering and space-time clustering were analysed. Statistical analysis used the Chi square test, the Spearman non-parametric correlation test, the Walter and Elwood test for seasonality of events and Knox analysis for time and space-time clustering. Results: We identified 461 patients: 421 born in metropolitan France (incidence 5.12 [4.63–5.61]/100 000 live births), and 40 born in overseas territories. No significant regional variation in incidence was found in metropolitan France, while the incidence was higher in French Polynesia (incidence 29.4 [15.4–43.3]/100 000 live births) ( p<0.001). Seasonality, time-clustering and time-space clustering could not be demonstrated. Conclusions: 1) The incidence of BA was 5.7-fold higher in Polynesia than in metropolitan France. 2) Neither seasonal variation in incidence nor clustering was identified.

Eclampsia: is there a seasonal variation in incidence?

To clarify whether seasonal variation of temperature and humidity has any effect on the incidence of eclampsia. Eclampsia is the second major cause of maternal mortality in Pakistan. Data was collected monthwise for the year 1996 from 4 large Govt. teaching hospitals of 4 provincial metropolis of Pakistan. Each province has diverse climate with considerable variation of air temperature and humidity. There were 395 cases of eclampsia amongst 18,483 deliveries in 1996, giving an incidence of 2.14%. In Karachi (Sindh Province) with mild hot and humid climate and mild winter months, there was increase in eclampsia cases from April-July and in September. Otherwise the incidence remained stable. In Rawalpindi (Punjab Province) with moderately hot summer and cold winter, it was highest in hot season from May to September but was stable in winter. In Peshawar (N.W.F.P) and Quetta (Baluchistan Province) with more severe cold and dry winter the incidence peaked in winter and summer months both. The pattern of eclampsia cases showed variations in extremes of temperature but it was stable in mild weather. However, the statistical analysis revealed non-significant relationship of incidence of eclampsia with temperature when analysed by linear regression analysis.

Incidence of photosensitive epilepsy: a prospective national study

We undertook a prospective nationwide study to determine the incidence of photosensitive epilepsy (PE). Virtually all EEG departments in Great Britain (providing approximately 90% coverage of all EEGs performed on people with newly diagnosed seizures) screened cases referred to them over a 3 month period and identified all new cases of epilepsy (defined as one or more recognised seizures) whose first EEG showed a photoparoxysmal response (PPR) on intermittent photic stimulation (IPS). 191 cases were identified, 143 of whom had type 4 PPRs (generalised spike and wave on IPS) on their first EEG. The annual incidence of cases of epilepsy with type 4 PPRs on their first EEG was conservatively estimated to be 1.1 per 100,000, representing approximately 2% of all new cases of epilepsy. When restricted to the age range 7–19 years, the annual incidence rose to 5.7 per 100,000 — approximately 10% of all new cases of epilepsy presenting in this age range. To ascertain if there was a significant seasonal variation in PE, 5 EEG departments (which together contributed 15% of cases in the first study period) were visited during a second 3 month study period to identify all new cases of epilepsy with type 4 PPRs on their first EEG. No significant seasonal variation in incidence between summer and winter was found.

Does the time of diagnosis of Type 2 diabetes have a seasonal variation?

AbstractThis prospective, observational study from 1987 to 1990 inclusive, set in hospital diabetes clinics in Leicester City, England (population 287,000), sought to establish whether or not Type 2 diabetes has a seasonal variation in incidence. The dates of diagnosis of 833 newly diagnosed Type 2 diabetic patients were recorded and total monthly incidence over the four year period calculated. Seasonal incidence was assessed by the Edward's test and the test for uniformity on a circle. No seasonal variation in the incidence of Type 2 diabetes was demonstrated, X2=4.32, p=0.11 and X2=3.32, p=0.19 respectively. These findings suggest that, unlike Type 1 diabetes, seasonality plays no significant role in the presentation of Type 2 diabetes. No increase in health care provision is required to cope with seasonal variation in Type 2, unlike that for Type 1 diabetes.

The epidemiology of melioidosis in Ubon Ratchatani, northeast Thailand.

Melioidosis, or infection with Pseudomonas pseudomallei is an important cause of morbidity and mortality in South East Asia and Northern Australia. The epidemiology of melioidosis in Ubon Ratchatani, Northeast Thailand was studied over a 5-year period from 1987 to 1991. Rates and, when possible, the risks of developing melioidosis were calculated. The numerator was the number of culture-proven cases of melioidosis seen in the 1000-bed referral hospital of the province. The denominators were obtained from the population census, a survey of Health, Welfare and Use of Traditional Medicine, and the North Eastern Meterological Centre, Thailand. The average incidence of human melioidosis was 4.4 (95% confidence interval [CI]: 3.8-5.0) per 100,000. The disease affected all ages with the highest incidence in 40-60 years olds. Melioidosis was 1.4 (95% CI: 0.4-5.3) times more common in males than females. The disease showed a significant seasonal variation in incidence, and a strong linear correlation with rainfall (r = 0.7, 95% CI: 0.5-0.9) Adults exposed to soil and water in their work (most were rice farmers) had an increased risk of melioidosis (in the 40-59 year age group, relative risk = 4.1, 95% CI: 2.4-6.9). Most adult patients had an underlying disease (mainly diabetes mellitus) predisposing them to this infection. Melioidosis may result from either acute exposure to the organism in the soil and water, or 're-activation' of an asymptomatic childhood infection (by an unidentified possibly infective seasonal cofactor). The results from this analysis are consistent with both hypotheses. Further epidemiological studies are needed to identify risk factors so that optimal strategies for control of melioidosis may be developed.

The epidemiology of diabetes mellitus in the United Kingdom: The Yorkshire regional childhood diabetes register

A register of the incidence of Type 1 (insulin-dependent) diabetes mellitus in the Yorkshire region of the United Kingdom has been completed. A total of 1,490 subjects aged between 0 and 16 years were identified from 1978 to 1990, giving an incidence of 13.7 per 100,000 (ages 0-14) or 13.6 per 100,000 (ages 0-16), comparable to other recent studies in the United Kingdom. An age-period-cohort analysis shows evidence for a modest drift effect of 1.75% per year (95% confidence interval 0.28 to 3.25%). There is a marked epidemic pattern with peaks at 4-year intervals. The age-incidence curve is similar to that reported elsewhere, having peaks in early childhood and puberty. Girls have an earlier pubertal peak than boys. There is substantial seasonal variation in incidence confined to those over 5 years of age. Ascertainment is believed to be very complete, and is estimated to be 97.6% (95% confidence interval 97.2% to 98.1%).

Limb fracture pattern in different pediatric age groups: a study of 3,350 children.

The fracture patterns of 3,350 children with 3,413 limb fractures admitted to one center from 1986 to 1990 were analyzed retrospectively. The overall boy-to-girl ratio was 2.7:1, rising to 5.5:1 in the adolescent group. Distal radius fracture was the most common fracture (19.87%), followed by supracondylar fracture of the humerus (16.64%) and forearm shaft fracture (13.36%). Specific age group breakdown showed that supracondylar fracture of the humerus was the most common fracture occurring in the age groups 0 to 3 years and 4 to 7 years, accounting for 28.94 and 31.18% of all limb fractures, respectively. Fracture of the distal radius occurred in 27.06% of the 8 to 11 year age group and 23.31% of the 12 to 16 year group. Open fractures were uncommon (2.17%), and greenstick fractures were found only in 5.27% of this hospital series. The nondominant arm was found to have more fractures although the number was not statistically significant. Seasonal variation in incidence occurred, with more cases in the summer and autumn months. The open reduction rate in the treatment varied from 10.15% in the 0 to 3 year age group to 33.95% in the 12 to 16 year group. Forty-five percent of the 0 to 3 year age group were discharged from hospital within 24 h, contrasting with 30% in the other age groups. Overall incidence of fractures requiring hospital treatment was estimated to range from 35 per 10,000 in the 0 to 3 year age group to 62, 60, and 57 per 10,000 in the 4 to 7, 8 to 11, and 12 to 16 year groups, respectively.

Suicidal acts on metro systems: an international perspective.

Suicide is a problem experienced by railway networks worldwide. The epidemiology of this method of suicide has not been described in any detail. To investigate the characteristic features of railway suicide, data were gathered from 23 metro systems around the world. The similarities in the nature of this problem across systems were striking. Universally the victims were young (aged less than 40 years); most incidents involved men; case fatality was generally less than 60%; there was no consistent seasonal variation in incidence; the peak time of day for incidents was 1000-1200; proximity to psychiatric institutions was possibly a risk factor. This method of suicide may be prevented by environmental modification of the railway system. Strategies for reducing the opportunities for suicide on railways are discussed.

Seasonal variation of cerebral hemorrhage in 236 consecutive cases in Brussels.

Seasonal variation in the incidence of cerebral hemorrhage has been previously demonstrated. In this study, we sought to identify the climatological data best correlated with this seasonal variation. In a retrospectively studied sequential series of 236 patients with nontraumatic cerebral hemorrhage observed in Brussels over a period of 8 years, we cumulatively grouped the dates of stroke occurrence into a single calendar year. We found marked seasonal variation in incidence, with the highest value (23%) observed in November-December and the lowest (10%) in July-August. Seasonal variations in incidence of cerebral hemorrhage were shown to be correlated not only with the inverse of ambient temperature, but also with the inverse of hours of sunshine and with ambient humidity. We found no difference between hypertensive and normotensive patients. Our study fails to bear out the hypothesis that the higher incidence of cerebral hemorrhage in late autumn and winter is due to the influence of low ambient temperature on blood pressure.

The Epidemiology of Acute Appendicitis in California

The incidence of acute appendicitis has been reported to vary substantially by country, geographic region, race, sex, season, and occupation, but the reasons for this variation are unknown. We evaluated several risk factors for appendicitis by analyzing data from hospital discharge abstracts on all cases of acute appendicitis treated surgically in nonfederal hospitals in California from 1983 to 1986 (N = 102,546). Comparison of age and sex-specific incidence rates for four racial/ethnic groups (white, Hispanic, black, and Asian/other) revealed rates in blacks and the Asian/other group one-half or less of the rates for whites and Hispanics between the ages of 5 and 29 years. Incidence rates in males were higher than rates in females in all racial/ethnic groups for most ages (RR = 1.1-1.7). Seasonal variation in incidence was modest. Peak rates occurred in July, August, and September, and the lowest rates occurred in December. Hypotheses about the etiology of appendicitis must account for substantial racial/ethnic, gender, age variation, and modest seasonal variation in the incidence.

Infantile meningitis in England and Wales: a two year study.

A two year prospective study identified 1922 cases of meningitis in children under 1 year of age. A further 201 cases were identified from other sources. The annual incidence of meningitis during the first year of life was 1.6/1000; during the first 28 days of life it was 0.32/1000, and among postneonatal infants it was 1.22/1000. The male:female ratio was 1.4:1. The overall case fatality rate was 19.8% for neonates and 5.4% for postneonatal infants. Two thirds of deaths identified in the study, 50% of all deaths, were not attributed to meningitis by the Office of Population Censuses and Surveys. Group B beta haemolytic streptococci (28%), Escherichia coli (18%), and Listeria monocytogenes (5%) were most frequently isolated from neonates and Neisseria meningitidis (31%), Haemophilus influenzae (30%), and Streptococcus pneumoniae (10%) from postneonatal infants. At 2-6 months of age N meningitidis meningitis was most common, and at 7-12 months H influenzae predominated. Meningitis caused by group B beta haemolytic streptococci occurred up to 6 months of age and had a consistent mortality of 25%. Neonatal meningitis due to Gram negative enteric rods had a mortality of 32%. Low birth weight was a significant predisposing factor for both neonates and postneonatal infants. In both groups mortality was significantly higher among children admitted in coma. There was no seasonal variation in incidence in either group. Neonates were treated with either group. Neonates were treated with either chloramphenicol (50%) or gentamicin (48%) usually in combination with a penicillin; 40% received a third generation cephalosporin. Of the 1472 postneonatal infants treated 84% received chloramphenicol with a penicillin and 10% received a third generation cephalosporin. Relapse occurred in 49 patients and three died. Eighteen babies coned as a result of raised intracranial pressure, including four neonates, and four died. Mortality among the 133 (7%) children who received steroids was significantly higher than in the rest of the study group.

Seasonal variation in stroke incidence in Hisayama, Japan.

We investigated seasonal variation in the incidence of cerebral stroke among the general population aged greater than or equal to 40 years in November of 1961 in Hisayama, Japan. During the 24-year follow-up period, 311 cases of cerebrovascular diseases occurred. The date or month of onset was determined in 308 cases, of which 51 were classified as intracerebral hemorrhage, 223 as cerebral infarction, and 27 as subarachnoid hemorrhage. We observed a significant seasonality in the incidence of all stroke (p less than 0.01), of intracerebral hemorrhage (p less than 0.05), and of cerebral infarction (p less than 0.01), whereas subarachnoid hemorrhage had no significant seasonal pattern. Subjects less than 64 years of age showed a significant seasonal variation in the incidence of both intracerebral hemorrhage (p less than 0.05) and cerebral infarction (p less than 0.01). A significant seasonal pattern for the incidence of intracerebral hemorrhage was also noted among persons with hypertension (p less than 0.05) or a high serum cholesterol level (p less than 0.05), whereas such a pattern for cerebral infarction was documented among normotensive persons (p less than 0.05) and those with a low serum cholesterol level (p less than 0.01). In addition, the incidences of intracerebral hemorrhage and cerebral infarction were negatively correlated with mean ambient temperature (p less than 0.01 and p less than 0.05, respectively), and all stroke and intracerebral hemorrhage in men were significantly related to intradiurnal temperature change (p less than 0.05 and p less than 0.01, respectively). The significance of the seasonal occurrence of stroke is discussed in relation to relevant risk factors.

Telematics: a new tool for epidemiological surveillance of diarrhoeal diseases in the Aquitaine sentinel network.

A sentinel health information system using telematics and a network of general practitioners was set up in Aquitaine in south western France in 1986. Among the health problems under surveillance was acute diarrhoea. Data for each patient who fulfilled the usual case definition for acute diarrhoea were reported by general practitioners using home terminals (Minitels) connected to a central computer by telephone. Over one year 2234 cases of diarrhoea were reported, the incidence varying from 0.8 to 1.5 cases per doctor per week. Seasonal variations in incidence were observed, with peaks in the winter and in the summer. Only 379 (17%) episodes of diarrhoea were classified as severe, and these patients consulted their general practitioners earlier than patients whose diarrhoea was less severe. Foreign travel was rarely found in the patients' histories, but clusters of cases were found in communities (4.6%) and in families (22.3%). The advantages of this system were easy reporting and immediate feedback, but it was difficult to extrapolate the data, and the system was inadequate for intervening in outbreaks of diarrhoeal disease. Our knowledge of diarrhoeal diseases in south west France improved.

A study of etiologic factors for cleft lip and palate in Sri Lanka.

Fifty-eight infants with cleft lip and/or cleft palate detected in a prospective study and 443 cleft patients in a retrospective study were investigated regarding seasonal variation of incidence, relation to birth rank, consanguinity of parents, and history of viral infections and drugs taken by mothers during the first trimester of gestation. The highest incidence was recorded in the month of April, but no reason for this could be found. No significant relation to birth rank and consanguinity of parents existed. Furthermore, the proportion of mothers of cleft patients who had taken drugs or who had viral infections was not significantly greater than in the control groups. These findings support the view that orofacial clefts probably have a multifactorial etiology.

Incidence of acute glaucoma in Finland from 1973 to 1982.

The incidence of acute closed-angle glaucoma was studied in 1796 patients derived from the hospital discharge registry of Finland for the years 1973-1982 (469 males and 1327 females). The average incidence was 3.8 cases/100,000 per year. The incidence showed a steep rise with age. The highest incidence was observed in both sexes in the group 80 years of age and older. The incidence was higher (Chi-square 7.81, df = 1, P less than 0.01) among women (5.3/100,000 per year) than among men (2.0/100,000 per year). The age-adjusted incidence for the whole period of 1973-1982 showed no statistically significant rise. The seasonal variation of incidence was statistically significant (P less than 0.001). In winter (December, January, February) and in autumn (September, October, November) the incidences were higher compared to spring (March, April, May) and summer (June, July, August). This association was greater (P less than 0.001) among females than among males (P less than 0.05). Mean sunshine hours showed a reverse association with the incidence of acute glaucoma. The association was statistically significant when both sexes were pooled together (P less than 0.001). There was no sex interaction with regard to the association of incidence of acute glaucoma and mean sunshine hours.

Bark stripping damage by red deer in a Sitka spruce forest in Western Scotland. I. Incidence

Bark stripping was monitored over a seven-year period on 240 permanent plots in Glenbranter Forest, Argyll. Sharp seasonal variation in incidence was found, rates being greatest in winter (December–March) and least in summer. There was very little damage in high-canopy ** forest (>44 years of age) or at the establishment stage (0–8 years). although 0.6 per cent y −1 of these younger trees were frayed. Trees aged 9–14, 15–28 and 29–44 years had mean rates of damage of 0.6, 1.0 and 0.5 per cent y −1 respectively. Norway spruce, only present in the pole and high-canopy stages, was more severely damaged than Sitka spruce. The incidence of bark stripping was patchy, the trees found damaged in the 3-month observation periods often being near neighbours. Over 2-year periods 74 per cent of the plots received no damage, but on 2 per cent of the plots >10 per cent of the trees were bark stripped. At such ‘hot-spots’ the intensity of damage was usually much lower in the preceding and following periods. However, individual trees suffered repeated bark stripping more often than would be expected by chance although the likelihood of repeated damage declined as time after the initial wounding increased. The trees damaged were quite variable in girth; their size was average on plots with mean girth of 20–40 cm, significantly bigger than average when mean girth was < 20 cm, and smaller than average above 40 cm mean girth. Rates of damage were not related to the number of red deer pellet groups deposited on 15×5 m plots; most dung occurred on vegetated plots yet bark stripping was commonest on plots without vegetation. But when plots within each forest stage were classified according to their position, most damage was found in the spatial zone with most dung (edge in thicket and high-canopy forest, interior in pre-thicket and polestage forest).

Epidemiology of insulin-dependent diabetes mellitus in Canterbury, New Zealand

A prospective study of incidence and prevalence of insulin-dependent diabetes mellitus in persons under 20 years was conducted over a 4-year period (1 February 1982-1 February 1986) for the Canterbury Hospital Board (total population 342,000) area in New Zealand. A central register for the area was established at the beginning of the study period. Degree of ascertainment was close to 100%. Average annual incidence was 11.7 persons per 100,000 (females: 10.6 per 100,000; males: 12.7 per 100,000) with no significant sex difference or temporal trends. Incidence peaks were seen for both sexes in the pubertal ages (females: 11 years; males: 13 years), with minor peaks occurring for both sexes in the pre-school ages. Age of onset was significantly younger in females than males. A seasonal variation in incidence was seen for males, with peaks in late autumn and mid-winter. 5.7% of the new diabetics had a first-degree relative with insulin-dependent diabetes mellitus. Islet cell cytoplasmic antibodies were detected in 68% of new diabetics and in 0% of age- and sex-matched healthy controls. Thyroid, gastric and adrenal auto-antibodies were seen more frequently in diabetics than in controls, but this difference was not significant. Prevalence of insulin-dependent diabetes on 1 February 1982 was 1.00 per 1000 and 1.05 per 1000 on 1 February 1986. The insulin-dependent diabetes mellitus incidence characteristics noted for the Canterbury Hospital Board area are similar to those reported for European and North American populations.

Legionnaires' disease: a review of 79 community acquired cases in Nottingham.

Seventy nine cases of sporadic, community acquired legionnaires' disease have been reviewed. Annual and seasonal variation in incidence was noted. The mean age of the patients was 53 years and 50 (63%) were male. Pre-existing chronic diseases were present in only 23 (29%), including two patients receiving immunosuppressive treatment. Common symptoms included unproductive cough, dyspnoea, chest pain, headache, confusion, nausea, vomiting, and diarrhoea. Respiratory symptoms were absent, however, in 17 (22%). Localising chest signs were present in 74 (95%) cases. Frequent laboratory findings included lymphopenia, high erythrocyte sedimentation rate, hyponatraemia, raised urea and creatinine concentrations, abnormal liver function, hypophosphataemia, hypoalbuminaemia, proteinuria, and haematuria. Thirteen patients died (16%), including nine of 20 who received assisted ventilation. The mortality rate in patients treated with erythromycin (11%) was lower than in those who received other antibiotics (23%), but this difference was not statistically significant. Of the features noted on admission, only a high plasma urea concentration was significantly associated with death. Sporadic community acquired legionnaires' disease is a not uncommon disorder, which with appropriate treatment has a prognosis similar to that of other forms of community acquired pneumonia.

Insulin dependent diabetes in under 5 year olds.

Insulin dependent diabetes mellitus presenting in children under five years old exhibits several clinical and management features that differ from diabetes presenting in older children. In this review of the current population of the Oxford children's diabetes clinic, children with diabetes diagnosed aged 0- less than 5 years are compared with those diagnosed aged 5- less than 10 years to illustrate these differences. The mean annual age specific incidence of diabetes for children aged 0- less than 5 is 9.9/100 000 compared with 13.8/100 000 for the children diagnosed aged 5- less than 10. Although children with diabetes currently aged less than 5 comprise only 8% of the clinic population, such children ultimately make up 41% of the total number of children with diabetes aged under 15 attending the clinic. Diabetes diagnosed in children under the age of 5 seems to have increased in incidence over the past 10 years, exhibits a male preponderence (1.5:1), and shows an unusual seasonal variation in incidence with an autumn/early winter trough, late winter/early spring peak, and the absence of mid-summer trough seen in other age groups. First degree family history was positive in 16% of children diagnosed under the age of 5 compared with 10% of the group diagnosed aged 5- less than 10. In none of these children was the mother the affected relative.

Seasonal variation in incidence of cerebellar medulloblastoma

The incidence of 16 cerebellar medulloblastoma admitted to the University Hospital of Leuven during the last 8 years shows a seasonal peak between September and December.