Seasonal Variation In Births Research Articles

Lyme Disease Models of Tick-Mouse Dynamics with Seasonal Variation in Births, Deaths, and Tick Feeding.

Lyme disease is the most common vector-borne disease in the United States impacting the Northeast and Midwest at the highest rates. Recently, it has become established in southeastern and south-central regions of Canada. In these regions, Lyme disease is caused by Borrelia burgdorferi, which is transmitted to humans by an infected Ixodes scapularis tick. Understanding the parasite-host interaction is critical as the white-footed mouse is one of the most competent reservoir for B. burgdorferi. The cycle of infection is driven by tick larvae feeding on infected mice that molt into infected nymphs and then transmit the disease to another susceptible host such as mice or humans. Lyme disease in humans is generally caused by the bite of an infected nymph. The main aim of this investigation is to study how diapause delays and demographic and seasonal variability in tick births, deaths, and feedings impact the infection dynamics of the tick-mouse cycle. We model tick-mouse dynamics with fixed diapause delays and more realistic Erlang distributed delays through delay and ordinary differential equations (ODEs). To account for demographic and seasonal variability, the ODEs are generalized to a continuous-time Markov chain (CTMC). The basic reproduction number and parameter sensitivity analysis are computed for the ODEs. The CTMC is used to investigate the probability of Lyme disease emergence when ticks and mice are introduced, a few of which are infected. The probability of disease emergence is highly dependent on the time and the infected species introduced. Infected mice introduced during the summer season result in the highest probability of disease emergence.

Seasonal Variation of Nonsyndromic Orofacial Clefts in Northern Chinese Population.

Nonsyndromic orofacial clefts (NSOC) comprise a range of disorders affecting the lips and oral cavity. Various authors evaluated seasonal influence on the occurrence of NSOC differently. The aim of present study was to investigate seasonal variation in birth of individuals with orofacial cleft in northern China. A retrospective study comprised 499 cases and 452 controls were conducted. Children with NSOC operated in The First Affiliated Hospital of Harbin Medical University from 2009 to 2015 were investigated. Controls were children patients with trauma and bone fracture from the same hospital during the same period. Data on sex, birth time, area of residence was retrospectively collected from patients' records. Chi-squared test was used for comparisons. P values less than or equal to 0.05 were considered to be significant. Seasonal distribution was significantly different between cases and controls (P < 0.05). Birth time peaks of cases, especially males, occurred in winter. Furthermore, compared with controls, more cases with cleft lip/palate were born in winter (P < 0.05). There was no significant seasonal difference between female cases and controls (P > 0.05), and no statistical difference was found between cases with cleft palate and controls (P > 0.05). Our study revealed the presence of seasonal variation in individuals with orofacial cleft in northern Chinese population. We found a peak incidence of birth time for NSOC during winter.

Neonatal vitamin D status and risk of childhood epilepsy.

Epilepsy is a nervous system abnormality that may be caused by unknown exposures during fetal development. Studies have shown neuroprotective effects of early exposure to vitamin D in other neurological disorders, and seasonal variation in birth of children with epilepsy. We aimed to investigate if neonatal 25(OH)D3 was associated with risk of childhood epilepsy. This case-cohort study compared neonatal 25(OH)D3 levels from children with epilepsy (n=403) and a random selected cohort of controls (n=1163), assessing the hazard of first epilepsy diagnosis between 1 and 4years of age from a weighted Cox proportional hazard model. Analyses were adjusted for parental education, maternal age, maternal epilepsy, maternal ethnicity, and gestational age, and additionally for season of birth and smoking during pregnancy. The mean (standard deviation [SD]) of neonatal 25(OH)D3 levels were 30.8(19.6)nmol/L among cases and 28.5(19.4)nmol/L among the cohort. The hazard ratio (HR) of epilepsy was in a dose-response pattern higher among children from the highest neonatal 25(OH)D3 quintiles (P-trend=.004). Results were unchanged after including season of birth in the analysis, where a significantly higher HR of epilepsy was observed among children in the two highest quintiles compared to children in the lowest quintile (Q4: HRadj 1.62, 95% CI 1.07-2.47 and Q5: HRadj 1.86, 95% CI 1.21-2.86). In this study, the risk of childhood epilepsy increased with neonatal 25(OH)D3 categories in a dose-response pattern, suggesting an association between a high neonatal 25(OH)D3 and the risk of childhood epilepsy. Considering that adjusting for season of birth strengthened the results, we conclude that maternal intake of vitamin D, and not vitamin D from sun exposure, was the vitamin D source associated with epilepsy. Although we cannot, in the present study, control for compounds in the diet like pollutants or heavy metals, which may correlate with dietary vitamin D, future studies investigating fetal origin of epilepsy should focus on compounds correlating with vitamin D.

Fecundity and human birth seasonality in Sweden: a register-based study

BackgroundIt is well-established that couples’ fecundities vary widely. Each couple has a relatively constant monthly probability of conceiving, which can vary from zero to quite high. This underlying probability is usually expressed as the time (number of menstrual cycles) the couple requires to conceive. Couples with high fecundity will, on average, need fewer cycles than couples with low fecundity. It is also well-documented that almost all human populations exhibit seasonal variation in births. Most European countries show seasonal variation that usually peak in the spring and are the lowest during the last quarter of the year. The increasingly strong pattern of depressed birth rates in November and December is likely explained by the December–January cut-off threshold for Swedish pupils’ school entry and their parents increasing awareness of the negative effects on school outcomes for children who are juniors in the school-entry cohort they belong to. To actively plan births for a specific time of the year, couples need to have some knowledge of the time required for them to conceive.MethodsWe use the duration between marriage of childless couples and first birth as a proxy measure of couples’ fecundity. Based on this time-to-pregnancy measure we study to what extent couples’ capacity to conceive affects the seasonality of their second births. We hypothesize that in a society with highly controlled fertility and a strong norm of having at least two children, sub-fertile couples will on average show less seasonal variation in second births. Sub-fertile couples, requiring more time to conceive the first time, will be less likely to try to target a desired birth month for their second child because doing so could jeopardize fulfilling their desired family size. We apply multinomial logistic regressions on 81,998 Swedish couples who married while being childless and subsequently gave birth to at least two children between 1990 and 2012, to investigate fecundity’s role in seasonal variation in second births.ResultsWe found that seasonal variation in second births was strongly associated with couples’ observed fecundity, measured as the duration between marriage formation and first birth. Our results support the hypothesis that sub-fertile couples, requiring more time to conceive the first time, show less seasonal variation in second births. The seasonal variations in second order births among couples with normal fecundity shows some similarities to traditional patterns as seen in agricultural and industrial societies of the past, with high numbers of births during the spring, and low numbers during the last quarter of the year. However, two important differences are notable. The characteristic Christmas peak in September has vanished, and the low birth rates in November and December come out much stronger than in the past.ConclusionsThe birth seasonality among couples with normal fecundity are what we would expect if couples actively plan their births according to the cut-off date for Swedish pupils’ school entry. We argue that our findings support the notion that scheduled childbirth is a reality in contemporary sociality.

Changing seasonal variation in births by sociodemographic factors: a population-based register study.

STUDY QUESTIONHave seasonal variations in births by factors related to maternal education, age, parity and re-partnering changed over a 72-year period?SUMMARY ANSWERSeasonal variation in births has been reduced overall but also changed its pattern over the last seven decades.WHAT IS KNOWN ALREADYThe number of births varies markedly by season, but the causes of this variation are not fully understood. Seasonality of births is, in some populations, strongly influenced by sociodemographic factors.STUDY DESIGN SIZE, DURATIONA longitudinal study design was used by analysing the seasonal variation in live births between 1940 and 2012, and relating it to mothers’ sociodemographic characteristics at the time of childbirth (maternal education, age, parity and re-partnering).PARTICIPANTS/MATERIALS, SETTING, METHODSRegister data on 6 768 810 live births in Sweden between 1940 and 2012 were used. Information on biological parents are available for more than 95% of all births. Multinomial logistic regressions were used to calculate predicted probabilities of giving birth for each calendar month.MAIN RESULTS AND THE ROLE OF CHANCEBetween 1940 and 1999, Swedish birth rates showed the typical seasonal variation with high numbers of births during the spring, and low numbers of births during the last quarter of the year. However, during the 21st century, the seasonal variation in fertility declined so that only minor variation in birth rates between February and September now remains. Still, the pattern of low birth rates at the end of the year remains and has even become more pronounced from the 1980s onwards. The characteristic ‘Christmas effect’ that used to be visible in September has vanished over the last 30 years. The roles in seasonal variation of maternal education, the mother’s age, parity and instances where the mother has re-partnered between subsequent births changed during the second half of the 20th century. From 1980s onwards, the decline in birth rates during the last quarter of the year became particularly pronounced among highly educated mothers. Over the 72 years studied, the seasonal variation among first-time mothers declined steadily and has almost disappeared at the end of the study period. Using data that cover ~180 000 births in each month, all meaningful results are statistically significant.LIMITATIONS REASONS FOR CAUTIONThe study uses data from one Nordic country only, making it difficult to draw conclusions that may hold for other countries.WIDER IMPLICATIONS OF THE FINDINGSThe typical seasonal variation reported for Sweden between 1940 and 1999, with high numbers of births during the spring and low numbers of births during the last quarter of the year, is in line with results from most other European countries during the same time period. However, the significant decline in seasonal variation in the early 21st century is a novel development. The study underlines that in a society with low fertility and efficient birth control, active choices and behaviours associated with an individual’s sociodemographic characteristics tend to matter more for the seasonal timing of childbearing than environmental factors related to the physiological ability to reproduce and cultural–behavioural factors related to the frequency of intercourse.STUDY FUNDING/COMPETING INTEREST(S)The study was funded by the Swedish Research Council (Vetenskapsrådet) via the Swedish Initiative for Research on Microdata in the Social and Medical Sciences (SIMSAM): Stockholm University SIMSAM Node for Demographic Research (grant registration number 340-2013-5164). The authors declare no conflicts of interest.TRIAL REGISTRATION NUMBERNot applicable.

The Demographics of Canine Hip Dysplasia in the United States and Canada.

Canine hip dysplasia (CHD) is a common problem in veterinary medicine. We report the demographics of CHD using the entire hip dysplasia registry from the Orthopedic Foundation for Animals, analyzing differences by breed, sex, laterality, seasonal variation in birth, and latitude. There were 921,046 unique records. Each dog was classified using the American Kennel Club (AKC) and Fédération Cynologique Internationale (FCI) systems. Statistical analysis was performed with bivariate and logistic regression procedures. The overall CHD prevalence was 15.56%. The OR for CHD was higher in females (1.05), those born in spring (1.14) and winter (1.13), and those in more southern latitudes (OR 2.12). Within AKC groups, working dogs had the highest risk of CHD (OR 1.882) with hounds being the reference group. Within FCI groups, the pinscher/molossoid group had the highest risk of CHD (OR 4.168) with sighthounds being the reference group. The similarities between CHD and DDH are striking. Within DDH there are two different types, the typical infantile DDH and the late onset adolescent/adult acetabular dysplasia, with different demographics; the demographics of CHD are more similar to the later onset DDH group. Comparative studies of both disorders should lead to a better understanding of both CHD and DDH.

Birth seasonality in rural areas of Iran, analysis of 5,536,262 births from 1992 to 2007

PurposeWe conducted this study to investigate birth seasonality in rural parts of Iran. MethodsIn this study, patterns of 5,536,262 live births in rural parts of Iran between 1992 and 2007 were studied. Information about birth numbers, environmental factors, and sociocultural status of participants was obtained from previous works. Visually inspecting the seasonal variation of birth, studying its trend using autocorrelation analysis, examining the trend of birth seasonality using the seasonality coefficient, a newly introduced index, studying correlations between birth seasonality and possible associated factors, and analyzing associations between these variables and birth seasonality using multiple regression model were performed in this study. ResultsIn this study, we showed birth seasonality in rural parts of Iran, with the highest births in the first two seasons, winter and spring, mostly before the year of 2002. Latitude and mean temperature of districts, wealth status of families, education of women, and mothers' ages were associated with birth seasonality. However, latitude, temperature, and mothers' ages lost their associations after adjusting for sociocultural factors in the regression model. ConclusionsBirth numbers in rural areas of Iran follow a rhythmic seasonal pattern; however, the ordering of seasons changes in the last years of the study period.

Season of birth is different in Inuit suicide victims born into Traditional than into Modern Lifestyle: a register study from Greenland.

BackgroundThere is growing evidence that living conditions at birth play a role in medical conditions later in life. Population-based studies from the Northern Hemisphere have shown that persons born in the spring or summer are at greater risk of committing suicide. A statistical correlation with light availability at birth has been observed in past research, but the cause remains unknown. Greenland is one of the most extreme of natural human habitats with regard to seasonal changes in light. The combination of rapid social changes and reliable population statistics offers a unique opportunity to make comparisons between persons born into a Traditional Lifestyle and those born into a Modern Lifestyle. The aim of this work was to assess whether season of birth differed between suicide victims born into an old or into a modern lifestyle.MethodsOfficial population and mortality registers were used. Suicide victims born (1903–1950) into the Traditional Lifestyle were compared with those born into the Modern Lifestyle (1961–1980). Rayleigh’s test for circular distributions was used to assess the season of birth in suicide victims. Data regarding season of birth in the general population were collected.ResultsPersons born in March-June in the Traditional Lifestyle were much less likely to commit suicide than those born during other periods of the year. This is contrary to the findings of other studies. The seasonal differences had disappeared for those born into the Modern Lifestyle. The suicide rate increased from very low rates to about 140 suicides/100 000 person-years in the 1980s.ConclusionsThe reason behind a variation in season of birth in suicide victims born into the old lifestyle is unknown. It is also unknown why the seasonal difference had disappeared with modern lifestyle. Possible influence of artificial light, nutrition, microbiota and seasonal infections are discussed. The underlying causes behind suicides may be different in traditional and modern Greenland.

No evidence of seasonality of birth in adult type 2 diabetes in Denmark.

The season of birth might influence prenatal circumstances, which may influence the risk of developing type 2 diabetes. The aim of this study was to determine whether the diagnosis of type 2 diabetes in Denmark changed with the season of birth. This study used data from the population-based Copenhagen School Health Records Register (CSHRR) that includes schoolchildren born between 1930 and 1989. Via a personal identification number, the CSHRR was linked to the National Patient Register containing hospital discharge diagnoses since 1977. The effect of seasonal variation in birth on the risk of type 2 diabetes was assessed using Cox regression, with month or season of birth as the predictor. The underlying time variable was age, and follow-up started in 1977 or at age 30years. The study population consisted of 223,099 people, of whom 12,486 developed adult type 2 diabetes. Using January as the reference month, the risk of type 2 diabetes by month of birth was not statistically different for any of the 11 comparative birth months. Grouping month of birth into seasons (spring was the reference) gave essentially similar results, showing no difference in the risk of type 2 diabetes for any season. Repeating the analysis by sex, birth cohort and birthweight categories revealed no associations. The risk of adult type 2 diabetes was not associated with month of birth in a large Danish population-based study. The results suggest that the causes of seasonality in birthweight are not causes of type 2 diabetes.

Season of birth and Parkinson's disease: possible relationship?

The amount of sun exposure in early life and consequent vitamin D3 level may influence the risk of developing Parkinson's disease (PD). Yet few studies have previously investigated birth trends in PD related to a possible seasonality and sun exposure. The aim of this study was to investigate a possible relationship between PD risk and sun exposure looking at seasonal birth variation of PD subjects in the homogenous geographic area of Naples, Italy. We selected 898 PD subjects and matched with 1796 controls. McNemar's test with Bonferroni correction and autocorrelation were used to test seasonality in birth trends. No difference was found for the month and season of birth between PD subjects and controls. We found a 3.3 % increase of PD female subjects born in September (3.3 %) and 4.1 % increase of PD male subjects born in spring comparing to controls but were not significant after Bonferroni correction. This study evaluated for the first time the seasonal birth trends in relation to PD risk in a Southern European population. We found no association between seasonal birth variations and risk of PD.

Birth seasonality in Korean Prader-Willi syndrome with chromosome 15 microdeletion.

PurposePrader-Willi syndrome (PWS) is a well-known genetic disorder, and microdeletion on chromosome 15 is the most common causal mechanism. Several previous studies have suggested that various environmental factors might be related to the pathogenesis of microdeletion in PWS. In this study, we investigated birth seasonality in Korean PWS.MethodsA total of 211 PWS patients born from 1980 to 2014 were diagnosed by methylation polymerase chain reaction at Samsung Medical Center. Of the 211 patients, 138 were born from 2000-2013. Among them, the 74 patients of a deletion group and the 22 patients of a maternal uniparental disomy (UPD) group were compared with general populations born from 2000 using the Walter and Elwood method and cosinor analysis.ResultsThere was no statistical significance in seasonal variation in births of the total 211 patients with PWS (χ2=7.2522, P=0.2982). However, a significant difference was found in the monthly variation between PWS with the deletion group and the at-risk general population (P<0.05). In the cosinor model, the peak month of birth for PWS patients in the deletion group was January, while the nadir occurred in July, with statistical significance (amplitude=0.23, phase=1.2, low point=7.2). The UPD group showed the peak birth month in spring; however, this result was not statistically significant (χ2=3.39, P=0.1836).ConclusionCorrelation with birth seasonality was identified in a deletion group of Korean PWS patients. Further studies are required to identify the mechanism related to seasonal effects of environmental factors on microdeletion on chromosome 15.

Seasonality of Poor Pregnancy Outcomes in North Carolina

Seasonal variation in poor pregnancy outcomes has not received the same level of research attention and rigor as has the well-established seasonal variation in births. In this analysis of data from the 2001-2005 North Carolina Detailed Birth Record, we use season of conception as a proxy for environmental or other risk factors. We model the continuous pregnancy outcome of birth weight percentile for gestational age by use of linear regression. We use logistic regression to model the binary pregnancy outcomes of low birth weight (< 2500 g), preterm birth (< 37 weeks), and small for gestational age (< 10th percentile of birth weight for gestational age). We found significant seasonal patterns in poor pregnancy outcomes. Our results suggest that, in North Carolina, seasonal patterns are most pronounced among non-Hispanic white women living in urban areas. The present study is limited by the restricted set of maternal and pregnancy variables available in this data set. Richer data, potentially including psychosocial and activity measures of the women, would allow us to more ably discern what is driving the seasonal patterns we observed. The pronounced increased risk associated with a spring season of conception provides an important clue for determining the true causative factors. Poor pregnancy outcomes in North Carolina follow a clear seasonal pattern based on timing of conception, with patterns most pronounced among non-Hispanic white women living in urban areas. These seasonal patterns are suggestive of causative environmental factors and certainly warrant additional research.

東京都における出生数の季節変動の分析 (1974-1983)

東京都における出生数の季節変動の分析 (1974-1983)

Infectious exposure in the first years of life and risk of central nervous system tumours in children: analysis of birth order, childcare attendance and seasonality of birth

Background:An infective, mostly viral basis has been found in different human cancers. To test the hypothesis of a possible infectious aetiology for central nervous system (CNS) tumours in children, we investigated the associations with proxy measures of exposure to infectious disease.Methods:In a large case–control study nested in the populations of Denmark, Norway, Sweden, and Finland of 4.4 million children, we studied the association of birth order and seasonal variation of birth with subsequent risk for CNS tumours. We identified 3983 children from the national cancer registries, and information on exposure was obtained from the high-quality national administrative health registries. We investigated the association between childcare attendance during the first 2 years of life and the risk for CNS tumours in a subset of Danish children with CNS tumours, using information from the Danish Childcare database.Results:We observed no association between birth order and risk of CNS tumours overall (odds ratio (OR) for second born or later born vs first born, 1.03; 95% confidence interval (CI), 0.96–1.10) or by histological subgroup, and children with CNS tumours did not show a seasonal variation of birth that was distinct from that of the background population. Childcare attendance compared with homecare showed a slightly increased OR (1.29; 95% CI, 0.90–1.86) for CNS tumours, with the highest risk observed in children attending a crèche. The strongest association was observed for embryonal CNS tumours. We found no effect of age at enrolment or duration of enrolment in childcare.Conclusion:These results do not support the hypothesis that the burden of exposure to infectious disease in early childhood has an important role in the aetiology of paediatric CNS tumours.

Modeling Susceptible Infective Recovered Dynamics and Plague Persistence in California Rodent–Flea Communities

Plague persists as an enzootic in several very different rodent-flea communities around the world. In California, a diversity of rodent-flea communities maintains the disease, and a single-host reservoir seems unlikely. Logistic regression of plague presence on climate and topographic variables predicts plague in many localities where it is absent. Thus, a dynamic community-based analysis was needed. Deterministic Susceptible Infective Recovered (SIR) models were adapted for plague and analyzed with an eye for insights concerning disease persistence. An R simulation program, Plaguesirs, was developed incorporating multihost and multivector SIR dynamics, demographic and environmental stochasticity, density dependence, and seasonal variation in birth and death. Flea-rodent utilization matrices allowed us to get transmission rates as well as flea carrying capacities. Rodent densities allowed us to estimate host carrying capacities, while maximum birth rates were mainly approximated through an examination of litter phenology and demography. We ran a set of simulations to assess the role of community structure in maintaining plague in a simulated version of Chuchupate campground in Ventura County. Although the actual campground comprises 10 rodent and 19 flea species, we focused on a subset suspected to act as a reservoir community. This included the vole Microtus californicus, the deer mouse Peromyscus maniculatus, the Ceratophyllid fleas Aetheca wagneri and Malareus telchinum, and the Leptopsyllid flea Peromyscopsylla hesperomys. The dynamics of 21 subsets of this community were simulated for 20 years. Single-rodent communities showed much lower disease persistence than two-rodent communities. However, so long as Malareus was present, endemicity was enhanced; removal of the other two fleas slightly increased disease persistence. Two critical features improved disease persistence: (1) host breeding season heterogeneity and (2) host population augmentation (due to two similar host species instead of one). Voles are winter-spring breeders compared to the spring-summer deer mice. While host synchronicity may enhance epidemics, host asynchronicity favors endemics.

Seasonal Variation in Birth and Diagnosis of Cancer in Children and Young People in Northern England, 1968-2005

ISEE-0062 Background and Objective: Seasonal variation is consistent with an environmental aetiology. The aim of this study was to investigate seasonal variation in cancer incidence in children and young people, using population-based data. Methods: Data on all cases diagnosed during the period 1968-2005 were extracted from The Northern Region Young Person's Malignant Disease Registry. The following diagnostic groups were analysed: leukaemia, lymphoma, central nervous system tumours, sympathetic nervous system tumours, retinoblastoma, renal tumours, hepatoblastoma, bone tumours, soft tissue sarcoma, germ cell tumours and carcinomas. The chi-squared heterogeneity test was used to test for departure from uniform distribution. Poisson regression analysis was used to fit sinusoidal (harmonic) models to the data, using month of birth and month of diagnosis, respectively, as covariates in separate models. The sinusoidal model assumption was assessed using the chi-square goodness of fit test. Analyses were carried out separately by gender and age group (0-14, 15-24 years). Results: There were a total of 5909 childhood cancer cases; 2959 aged 0-14 years (1659 males, 1300 females) and 2950 aged 15-24 years (1590 males, 1358 females). For 0-14 year old boys, there was statistically significant seasonal variation in month of birth for acute non lymphocytic leukaemia (P = 0.04; peak in September) and astrocytoma (P = 0.03; peak in October). Based on month of diagnosis, there was statistically significant seasonal variation in girls for lymphomas (P = 0.05; peak in March) and Hodgkin lymphoma (P < 0.01; peak in January), and in boys for osteosarcoma (P = 0.05; peak in October). For 15-24 year olds, significant seasonal variation in month of birth for malignant melanoma in females (P = 0.03; peak in March) and cervical carcinoma (P = 0.03; peak in October) was observed. Conclusion: These findings suggest that seasonal environmental factors, particularly around the time of birth, such as infections or exposure to sunlight may be involved in the aetiology of specific diagnostic groups.

Spatial and temporal investigations of reported movements, births and deaths of cattle and pigs in Sweden

BackgroundLivestock movements can affect the spread and control of contagious diseases and new data recording systems enable analysis of these movements. The results can be used for contingency planning, modelling of disease spread and design of disease control programs.MethodsData on the Swedish cattle and pig populations during the period July 2005 until June 2006 were obtained from databases held by the Swedish Board of Agriculture. Movements of cattle and pigs were investigated from geographical and temporal perspectives, births and deaths of cattle were investigated from a temporal perspective and the geographical distribution of holdings was also investigated.ResultsMost movements of cattle and pigs were to holdings within 100 km, but movements up to 1200 km occurred. Consequently, the majority of movements occurred within the same county or to adjacent counties. Approximately 54% of the cattle holdings and 45% of the pig holdings did not purchase any live animals. Seasonal variations in births and deaths of cattle were identified, with peaks in spring. Cattle movements peaked in spring and autumn. The maximum number of holdings within a 3 km radius of one holding was 45 for cattle and 23 for pigs, with large variations among counties. Missing data and reporting bias (digit preference) were detected in the data.ConclusionThe databases are valuable tools in contact tracing. However since movements can be reported up to a week after the event and some data are missing they cannot replace other methods in the acute phase of an outbreak. We identified long distance transports of cattle and pigs, and these findings support an implementation of a total standstill in the country in the case of an outbreak of foot-and-mouth disease. The databases contain valuable information and improvements in data quality would make them even more useful.

Seasonal variation in birth and diagnosis of cancer in children and young people in Northern England, 1968–2005

To investigate seasonal variation in the incidence of cancer in children and young people, using population-based data. Northern England, UK. Data on all cases were extracted from the Northern Region...

Season of Birth and the Risk of Uveal Melanoma

Purpose: To determine whether the risk of choroid and ciliary body melanoma varies according to season of birth. Methods: A case-control study design was used to determine odds ratio of choroidal and ciliary body melanoma for season of birth. Patients with histologically confirmed choroidal and ciliary body melanoma from 1995 through 2004 were identified from the Texas cancer registry. Controls were selected from the same registry. Results: 743 persons with choroidal and ciliary body melanoma were identified during the 10-year study period. There was no association between season of birth and odds ratio for developing choroidal and ciliary body melanoma. Conclusions: Although the risk of several types of brain tumors have been associated with birth during the winter, this case-control study found no statistically significant variation in season of birth and the development of choroidal and ciliary body melanoma.

Seasonality of birth in children with central nervous system tumours in Denmark, 1970-2003.

We investigated possible seasonal variation of births among children <20 years with a central nervous system tumour in Denmark (N=1640), comparing them with 2 582 714 children born between 1970 and 2003. No such variation was seen overall, but ependymoma showed seasonal variation.