Variation In Month Of Birth Research Articles

A review of seasonality of cleft births – The Brazil experience

AimsEvaluate the seasonal influence in nonsyndromic cleft lip and/or palate (NSCL/P) in Brazilian patients. MethodsA case-control study, with 361 unrelated patients with NSCL/P and 481 healthy individuals, was done on a reference service for craniofacial deformities in Minas Gerais State, Brazil. Information was collected from clinical records considering gender, month of birth, as well as with the seasons. ResultsNonparametric tests did not show a seasonal variation in month of birth and in seasons of year of NSCL/P compared to a control group (p=0.902 and p=0.679, respectively). A difference in births between the groups was identified only in January, however, was not significant. Moreover, among the control group there were more births in the months of February and August, and for the cleft group, more in July and August. The males were more affected by cleft lip with or without palate (CLP) and the females by isolated cleft palate (CP) manifestation. The ratio of CL:CLP:CP indicated that CLP was predominant when compared with CL and CP, CLP was more frequent in male patients, and CP predominance was seen in females. ConclusionThis study did not show seasonal differences in births on NSCL/P in a Brazilian group, emphasizing that environmental factors may be related to oral clefts. These results provide a basis for further epidemiological studies of orofacial clefts in Brazil.

An Economic Analysis of the Optimal School Starting Age

This study develops and empirically applies an approach to identify the optimal school starting age. Postponing school entry involves a tradeoff between better learning through higher maturity and higher opportunity costs through foregone time. We model a Skill Technology Function, where learning becomes more effective as children mature, and use variation in month of birth for multiple countries from multiple data sources to empirically estimate the slope and the curvature of this function. To compare student performance at different exact ages, we express test scores in age equivalents. This allows us to separate starting age effects from age of testing effects, and shows that birth month effects stabilize relatively early. Our main conclusion is that higher starting ages improve achievement in both the short and the long run, but, for most conventional starting ages, this effect does not compensate for incurred opportunity costs.

Seasonality in the Incidence of Cervical Carcinoma in Teenagers and Young Adults in Northern England, 1968–2005

Infection with human papillomavirus is an established risk factor for cervical carcinoma. However, the role of other environmental factors is less well established. To further investigate whether other agents may be involved, the authors have analyzed seasonal variation in cervical cancer with respect to month of birth and separately month of diagnosis. All 85 cases diagnosed in 15–24-yr-olds during the period 1968–2005 were extracted from the specialist population-based Northern Region Young Persons' Malignant Disease Registry. The chi-square heterogeneity test was used to assess overall nonuniform variation in month of birth and separately month of diagnosis. Poisson regression analysis was used to fit sinusoidal (harmonic) models to the data using month of birth and month of diagnosis in separate models. Based on month of birth, there was statistically significant heterogeneity (p = .03) and a significant sinusoidal pattern, with an incidence peak involving births in the autumn months (p = .03). Based on month of diagnosis, there was marginally significant heterogeneity (p = .06). The evidence of seasonal variation around time of birth for cervical carcinoma is highly novel and suggests possible early etiological involvement of environmental factors. (Author correspondence: Richard.McNally@ncl.ac.uk)

Month of birth is associated with multiple sclerosis but not with HLA-DR15 in Finland

Background: Spring birth has been found to be associated with increase in the risk of MS. However, this effect is reportedly found particularly in HLA-DR15 positive patients. Objective: Examine the month of birth (MOB) effect in Finnish MS patients and its association with HLA-DR15. Methods: Using the national register on hospitalizations during 1979–2004 we identified 8359 MS patients. We used a χ2-analysis to compare the distribution of MOB in MS patients versus age-adjusted controls. Patients were subdivided into 10-year birth cohorts to analyse temporal variations in MOB. A subgroup of HLA-typed MS patients (n = 657) and a population sample of healthy donors from the Finnish Bone Marrow Donor Registry (n = 19,805) were included to analyse connections between HLA-DR15 and MOB. Results: An April birth was associated with a 9.4% increased risk of MS (p = 0.008), whereas November birth was associated with an 11.1% decreased risk (p = 0.004) compared with the expected birth distribution. No temporal clustering in the MOB effect was found during 1900–1988. Both HLA-DR15 positive (34% increase, p = 0.043) and DR15 negative (48% increase, p = 0.0095) MS patients exhibited an increase in spring births (in May). HLA-DR15 in healthy subjects was not associated with MOB. Conclusions: We confirm that spring birth increases MS risk. This phenomenon was not associated with HLA-DR15 and there was no evidence of temporal clustering. The MOB effect suggests that early developmental processes may modulate MS risk.

Season of birth and diagnosis for childhood cancer in Northern England, 1968–2005

The aim of this study was to investigate seasonal variation in the incidence of cancer in children aged 0-14 years. Details of 2959 primary malignant cases (1659 males, 1300 females), diagnosed during the period 1968-2005, were extracted from a specialist registry (the Northern Region Young Persons' Malignant Disease Registry). Seasonal variation was analysed with respect to month of birth and diagnosis. The chi-squared heterogeneity test was used to test for non-uniform variation. 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. There was significant sinusoidal variation based on month of birth for acute lymphoblastic leukaemia (ALL) aged 1-6 years (P = 0.04; peak in March). For 0- to 14-year-old boys, there was statistically significant sinusoidal 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 sinusoidal variation in girls for all lymphomas (P = 0.048; peak in March) and Hodgkin lymphoma (HL) (P = 0.005; peak in January), and in boys for osteosarcoma (P = 0.049; peak in October). This study confirms previous findings of seasonal variation around the month of birth for childhood ALL (at the peak ages) and provides further evidence of seasonal variation around month of birth for astrocytoma and around month of diagnosis for HL. The results are consistent with a role for environmental factors in the aetiology of these diagnostic groups. Further studies are needed to examine putative candidate agents.

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.

Seasonal Variation and Regional Distribution of Cleft Lip and Palate in Zambia

To assess variations in seasonality and regional distribution of orofacial clefts in babies born in Zambia. A retrospective chart review was done using records of all cleft procedures performed by the only plastic surgeon in Zambia (G.J.). Delivery data from the University Teaching Hospital (UTH) were also examined to estimate the birth prevalence of orofacial clefts (55,108 live births between 2001 and 2005). All cleft patients operated in Zambia from 2000 to 2006 (413 patients). A low birth prevalence of clefts (1/4239 live births) was found using UTH delivery data. Surgical data showed no difference for the frequency of one gender over another overall (M:F ratio is 1.04; p = .70). More bilateral clefts occurred in cleft lip and palate (CLP) patients than in cleft lip (CL) patients (p < .01), and more unilateral left-sided clefts occurred in CL than in CLP patients (p = .03). The data reflected seasonal variation in month of birth of cleft lip with or without cleft palate (CL+/-P) patients (p < .01), with a peak in April and May and more births in March through August (57.2%) than in September through February (42.8%). There was regional variation in cleft births among the nine Zambian provinces (p < .01). This study shows seasonal variation in clefts that may be explained, at least in part, by environmental factors affecting the development of CL+/-P. Access to treatment is likely the major determinant of regional disparity in clefts. These results provide a basis for further epidemiological studies of orofacial clefts in Zambia.

Season of birth and eating disorders: Patterns across diagnoses in a specialized eating disorders service

In view of inconsistent findings from previous studies, the aim was to investigate possible seasonal variation in month of birth in patients with anorexia nervosa, bulimia nervosa, and eating disorder not otherwise specified. We examined the month of birth in a cohort of 1,305 adult patients with a DSM-IV eating disorder diagnosis at first presentation to a specialized eating disorders service. When compared to general population data, we found no evidence of significant variation in month or season of birth in anorexia nervosa, bulimia nervosa, or eating disorder not otherwise specified. The authors question whether people who develop eating disorders differ from the general population in their season of birth. Caution is expressed about further speculation regarding the etiological significance of season of birth in eating disorders.

Does the early bird catch the worm?

We estimate the effect of age of school entry on educational attainment using three different data sets for Germany, sampling pupils at the end of primary school, in the middle of secondary school and several years after secondary school. Results are obtained based on instrumental variable estimation exploiting the exogenous variation in month of birth. We find robust and significant positive effects on educational attainment for pupils who enter school at seven instead of six years of age: Test scores at the end of primary school increase by about 0.42 standard deviations and years of secondary schooling increase by almost half a year.

LACK OF SEASONAL VARIATION IN IDIOPATHIC TALIPES EQUINOVARUS

Background: One proposed etiology of idiopathic talipes equinovarus is an in utero enterovirus infection. Enterovirus infections demonstrate seasonal variation in temperate climates. Methods: We collected data on 1202 children with idiopathic talipes equinovarus born in the Northeastern United States, Midwestern United States, and the United Kingdom to investigate a seasonal variation in this congenital deformity. Birth date, gestational age at the time of delivery, gender, race, and laterality were tabulated and subjected to univariate and bivariate analyses. Results: There were 774 boys and 428 girls with idiopathic talipes equinovarus. The birth location was the United Kingdom (458 children), the Midwestern United States (426 children), and the Northeastern United States (318 children). No significant differences were detected among the geographic groups with respect to gender, race, or laterality, and no variation in month of birth or month of conception was noted. Conclusions: This study does not support an in utero enterovirus infection as an etiology of idiopathic talipes equinovarus in industrialized populations.

Lack of Seasonal Variation in Idiopathic Talipes Equinovarus

One proposed etiology of idiopathic talipes equinovarus is an in utero enterovirus infection. Enterovirus infections demonstrate seasonal variation in temperate climates. We collected data on 1202 children with idiopathic talipes equinovarus born in the Northeastern United States, Midwestern United States, and the United Kingdom to investigate a seasonal variation in this congenital deformity. Birth date, gestational age at the time of delivery, gender, race, and laterality were tabulated and subjected to univariate and bivariate analyses. There were 774 boys and 428 girls with idiopathic talipes equinovarus. The birth location was the United Kingdom (458 children), the Midwestern United States (426 children), and the Northeastern United States (318 children). No significant differences were detected among the geographic groups with respect to gender, race, or laterality, and no variation in month of birth or month of conception was noted. This study does not support an in utero enterovirus infection as an etiology of idiopathic talipes equinovarus in industrialized populations.

Seasonal variation in month of birth and diagnosis in children and adolescents with Hodgkin disease and non-Hodgkin lymphoma.

Infections have been hypothesized to be a risk factor for Hodgkin disease and non-Hodgkin lymphoma. Because infections usually occur seasonally, the authors looked at the seasonal pattern of occurrence of these diseases, since seasonal variation in occurrence would lend support to the hypothesis of an etiologic link between infection and lymphoma. The authors identified 575 patients with Hodgkin disease and 498 with non-Hodgkin lymphoma under the age of 20 years in the Danish Cancer Registry from 1943 to 1994. A periodic regression model was used to evaluate the seasonal distribution of month of diagnosis and month of birth. For the month of diagnosis of Hodgkin disease, the peak month of occurrence was March. The peak-to-trough ratio (the estimated incidence in the month of the peak divided by the estimated incidence in the month of the trough) was 1.57. For birth date, the ratio of case births at the peak month to case births at the trough month was 1.21, with a peak in July. There was no meaningful seasonal variation in the diagnosis or month of birth of children with non-Hodgkin lymphoma. These data corroborate a previously reported March peak in the diagnosis of Hodgkin disease.

Does month of birth affect risk of Crohn's disease in childhood and adolescence?

> Month of birth may be linked to risk of Crohn's disease later in childhood Early factors seem to have a role in the development of Crohn's disease later in...

Seasonality of birth for cancer in Northern England, UK.

Environmental factors operating around the time of birth may influence the subsequent development of childhood cancer, particularly leukaemia. Certain factors may vary with season (e.g. infections), and we therefore investigated whether there was any evidence of seasonality of month of birth, based on data from 4199 children diagnosed with cancer under the age of 15 years. We extracted details of (i) children born 1960-95 and diagnosed 1968-95 from two population-based registries, covering the Northern (n = 2053) and Yorkshire (n = 1977) Regional Health Authority and (ii) children born in Cumbria 1950-93 and diagnosed anywhere in the UK before 1994 from a birth cohort database (n = 397). The following diagnostic categories were analysed: 0-14 years--all cancers, leukaemias, acute lymphoblastic leukaemias, central nervous system tumours, all other solid tumours; 1-6 years--leukaemias, acute lymphoblastic leukaemias. Seasonal variation was tested using Walter and Elwood's test, and logistic regression analysis allowing for cyclical variation in month of birth. No evidence of seasonality was present for any group except acute lymphoblastic leukaemia diagnosed among 1- to 6-year-olds. Seasonal trends varied by region: in the Northern and Cumbrian datasets, seasonality patterns were significant and similar (P < 0.05) with a predicted peak in early spring, whereas in Yorkshire there was less strong evidence of seasonality (P = 0.08) with a peak predicted in late summer. These findings suggest that local seasonal environmental factors operating around the time of birth are not associated with the totality of childhood cancer, but possible links with acute lymphoblastic leukaemia are supportive of a hypothesis of an infectious aetiology.

Seasonal Variation in Month of Birth and Diagnosis of Early Childhood Acute Lymphoblastic Leukemia

Seasonal Variation in Month of Birth and Diagnosis of Early Childhood Acute Lymphoblastic Leukemia

Seasonal Variation in Month of Birth and Diagnosis of Early Childhood Acute Lymphoblastic Leukemia

Seasonal Variation in Month of Birth and Diagnosis of Early Childhood Acute Lymphoblastic Leukemia

Season of birth in schizophrenia: no latitude at the equator.

If the established winter excess in births of people who subsequently develop schizophrenia is an effect of 'seasonality', this would be testable by examining the pattern of births in an equatorial region with no formal seasons. To investigate whether there is any variation in month of birth among patients from equatorial Singapore with a diagnosis of schizophrenia. All 9655 patients discharged from Singapore's national psychiatric hospital with a diagnosis of schizophrenia were included (year of birth range 1930-1984). We analysed aggregated data, as well as the data of subsamples grouped according to birth-year periods, in order to examine secular trends. One patient subsample (those born 1960-84) allowed exact matching against the general population data set and close testing of any seasonal influence. Monthly variation in births was evident for both patients and controls; the patterns were very similar, apart from the patient sample showing a trough in March-April. In an equatorial region, where 'seasons' are absent, no seasonal excess in births of those later developing schizophrenia was evident.

Birth season and breast cancer risk in Japan.

Recent studies suggest that prenatal or early post-natal factors may influence future breast cancer risk. To investigate whether month of birth is a risk factor for breast cancer, we analyzed the distribution of month of birth for 81,162 women died of breast cancer and 1,334,650 women died of cancers at all sites, who were reported to the Ministry of Health and Welfare from 1972-90 in Japan. After considering each birth year seasonal variations in month of birth were not shown statistically significant in any age-group through using chi 2 test (df = 11). The negative results were also confirmed in residential area and period category.

Season of birth and autistic disorder in Israel

Variations in month of birth were examined in patients with infantile autism to test the hypothesis that birth in a particular month may be a risk factor for this disorder. Data for autistic patients registered with the National League for Autism in Israel (N = 188) during the years 1964-1986 were compared with data on monthly distribution of live births in Israel for the corresponding period. After risk ratio estimates were computed for children born with infantile autism for each month, a significant increase was observed for children born in March and August. This association was true for each year throughout the study. An additional finding was a significantly higher rate of birth of autistic children in the years 1970-1976. This study, although made in a different climatic area than three earlier studies, further emphasizes the earlier findings that March and August births are a risk factor for development of autistic disorder.

MONTH OF BIRTH AND TESTICULAR CANCER RISK IN DENMARK

On the basis of 40 years of national cancer registration, the authors analyzed the distribution of birth dates of patients with testicular cancer in the Danish male population, which has a particularly high incidence of this cancer. No significant peaks were identified, except for men with embryonal carcinomas born between 1950 and 1959, for whom a significant 12-month cycle was observed. This result differs from those of earlier studies. The number of cases of embryonal carcinomas in the 1950-1959 birth cohort is small, but it is possible that an etiologic factor that varies with season was present at the time. For all testicular cancers and for the three histologic subgroups analyzed, the authors found significant 2-month cycles. The biologic relevance of a 2-month cycle is not clear. It is concluded that there is little evidence to support the hypothesis of a systematic variation in month of birth among men with testicular cancer.