Risk Analysis of Respiratory Syncytial Virus Among Infants in the United States by Birth Month.

BACKGROUND: Respiratory syncytial virus (RSV) is a major cause of morbidity and mortality among US infants. A child's calendar birth month determines their age at first exposure(s) to RSV. We estimated birth month-specific risk of medically attended (MA) RSV lower respiratory tract infection (LRTI) among infants during their first RSV season and first year of life (FYOL). METHODS: We analyzed infants born in the USA between July 2016 and February 2020 using three insurance claims databases (two commercial, one Medicaid). We classified infants' first MA RSV LRTI episode by the highest level of care incurred (outpatient, emergency department, or inpatient), employing specific and sensitive diagnostic coding algorithms to define index RSV diagnoses. In our main analysis, we focused on infants' first RSV season. In our secondary analysis, we compared the risk of MA RSV LRTI during infants' first RSV season to that of their FYOL. RESULTS: Infants born from May through September generally had the highest risk of first-season MA RSV LRTI-approximately 6-10% under the specific RSV index diagnosis definition and 16-26% under the sensitive. Infants born between October and December had the highest risk of RSV-related hospitalization during their first season. The proportion of MA RSV LRTI events classified as inpatient ranged from 9% to 54% (specific) and 5% to 33% (sensitive) across birth month and comorbidity group. Through the FYOL, the overall risk of MA RSV LRTI is comparable across birth months within each claims database (6-11% under the specific definition, 17-30% under the sensitive), with additional cases progressing to care at outpatient or ED settings. CONCLUSIONS: Our data support recent national recommendations for the use of nirsevimab in the USA. For infants born at the tail end of an RSV season who do not receive nirsevimab, a dose administered prior to the onset of their second RSV season could reduce the incidence of outpatient- and ED-related events.

Birth characteristics as predictors of respiratory syncytial virus hospitalisation in newborns to optimise immunisation schedule.

AIM: To examine birth characteristics that influence infant respiratory syncytial virus (RSV) hospitalisation risk in order to identify risk factors for severe RSV infections. METHODS: Retrospective cohort study of 460 771 Sicilian children under 6 months old from January 2007 to December 2017. Hospital discharge records were consulted to identify cases and hospitalisations with International Classification of Diseases, Ninth Revision, Clinical Modification codes 466.11 (RSV bronchiolitis), 480.1 (RSV pneumonia) and 079.6 (RSV). RSV hospitalisation risk was estimated using adjusted odds ratios (aOR) and 95% confidence intervals (95% CI). RESULTS: Overall, 2420 (5.25 per 1000 infants) RSV-related hospitalisations were identified during the study, with girls accounting for 52.8%. RSV hospitalisation risk increased for full-term, transferred, extreme immature, and preterm neonates with serious issues (aOR 3.25, 95% CI 2.90-3.64; aOR 1.86, 95% CI 1.47-2.32; aOR 1.54, 95% CI 1.11-2.07; and aOR 1.48, 95% CI 1.14-1.90). Compared to children born in June, the risk of RSV hospitalisation was significantly higher in children born in January (aOR 28.09, 95% CI 17.68-48.24) and December (aOR 27.36, 95% CI 17.21-46.99). CONCLUSION: This study identified birth month and diagnosis-related groups as key predictors of RSV hospitalisations. This could help manage monoclonal antibody appropriateness criteria.

Season of birth and atopic dermatitis in early infancy: results from the Japan Environment and Children's Study.

BACKGROUND: Atopic dermatitis (AD) is reported to be more prevalent in children who were born in autumn than in spring. Here, we investigated how early the association between season of birth and eczema or AD can be observed in the postnatal period. We also examined whether specific prevalence outcomes for infant eczema and AD differed according to sex and maternal history of allergic disease in a large Japanese cohort. METHODS: Using data of 81,615 infants from the Japan Environment and Children's Study, we examined the associations of birth month or season with four different outcomes-eczema at 1 month, 6 months, and 1 year of age and physician-diagnosed AD up to 1 year of age-using multiple logistic regression analysis. We also analyzed the effect of maternal history of allergic disease on these outcomes stratified by infant sex. RESULTS: The risk of eczema at 1 month was highest in infants born in July. In contrast, infants born in autumn had higher risks of eczema at 6 months (adjusted odds ratio [aOR], 2.19; 95% confidence interval [CI], 2.10-2.30) and at 1 year (aOR, 1.08; 95% CI, 1.02-1.14) and of physician-diagnosed AD up to 1 year of age (aOR, 1.33; 95% CI, 1.20-1.47) compared with infants born in spring. Eczema and AD were more prevalent in infants with a maternal history of allergic disease, particularly boys. CONCLUSIONS: Our findings suggest that the prevalence of AD is associated with the season of observation. Eczema is prevalent in infants born in autumn, and this phenomenon was observed in infants as young as 6 months old. The risk associated with being born in autumn was particularly clear in boys with a maternal history of allergic disease. TRIAL REGISTRATION: UMIN000030786.

Systematic review and meta-analysis: Season of birth and schizophrenia risk.

OBJECTIVE: Winter birth has been hypothesized to be associated with increased schizophrenia risk for nearly a century. Major hypotheses regarding the potential etiological risk factors for schizophrenia such as vitamin D deficiency and virus exposure in utero are predicated based on the observation that risk of schizophrenia is higher in children born in winter months. METHODS: We conducted a systematic review and meta-analysis to examine the association between season and month of birth and risk of schizophrenia. We further investigated this relationship stratified by hemisphere. RESULTS: Forty-three studies spanning 30 countries and territories and 440,039 individuals with schizophrenia were included in this meta-analysis. Winter births were associated with a small but statistically significant increased risk of schizophrenia (OR 1.05, 95 % CI 1.03-1.07, p < 0.0001) and summer births were associated with a small but statistically significant decreased risk of schizophrenia (OR 0.96, 95 % CI 0.94-0.98, p = 0.0001). Stratified subgroup analysis demonstrated no significant difference between hemispheres in the risk of schizophrenia for either winter or summer births. CONCLUSIONS: Analysis using birth month data demonstrated a clear seasonal trend towards increased risk of schizophrenia being associated with winter birth months and decreased risk of schizophrenia in summer-to-fall months in the Northern but not Southern Hemisphere. These data suggest a small-but-substantial increased risk of schizophrenia in winter birth month. Further research needs to examine potential etiologic causes for this association.

The role of the relative age effect on talent identification in professional road cycling.

This study aims to investigate the presence of the relative age effect (RAE) in (semi-)professional cycling, especially within selecting cyclists for Continental (CT) development teams. Data were collected from www.procyclingstats.com (PCS). Cyclists out of the top-25 countries of the PCS ranking that were part of a CT team between 2005 and 2016 and born between January 1986 and December 1997 were included (n = 2854). Distributions of cyclists in different birth quarters (Q1, Q2, Q3 and Q4) as well as for different starting years at CT level (U23year1, U23year2, U23year3 and U23year4) and reaching professional level or not were investigated using the Chi-square goodness-of-fit test. A RAE was found for cyclists that did not reach professional level, which can be explained by cyclists starting at CT level U23year1 and U23year2 (19 and 20 years old). Meaning that for cyclists at 19 and 20 years old, there is a selection bias towards relatively older (Q1) cyclists at the expense of relatively younger (Q4) cyclists. Within the cyclists that reached professional level, no RAE was found, indicating that the RAE diminishes at professional level. This study provides insight into possible selection errors while selecting cyclists for CT development teams.

Respiratory Syncytial Virus Burden and Healthcare Utilization in United States Infants <1 Year of Age: Study of Nationally Representative Databases, 2011-2019.

BACKGROUND: Respiratory syncytial virus (RSV) is the leading cause of hospitalizations in United States infants aged <1 year, but research has focused on select populations. METHODS: National (Nationwide) Inpatient Sample and National Emergency Department (ED) Sample data (2011-2019) were used to report RSV hospitalization (RSVH), bronchiolitis hospitalization (BH), and ED visit counts, percentage of total hospitalizations/visits, and rates per 1000 live births along with inpatient mortality, mechanical ventilation (MV), and total charges (2020 US dollars). RESULTS: Average annual RSVH and RSV ED visits were 56 927 (range, 43 845-66 155) and 131 999 (range, 89 809-177 680), respectively. RSVH rates remained constant over time (P = .5), whereas ED visit rates increased (P = .004). From 2011 through 2019, Medicaid infants had the highest average rates (RSVH: 22.3 [95% confidence interval {CI}, 21.5-23.1] per 1000; ED visits: 55.9 [95% CI, 52.4-59.4] per 1000) compared to infants with private or other/unknown insurance (RSVH: P < .0001; ED visits: P < .0001). From 2011 through 2019, for all races and ethnicities, Medicaid infants had higher average RSVH rates (up to 7 times) compared to infants with private or other/unknown insurance. RSVH mortality remained constant over time (P = .8), whereas MV use (2019: 13% of RSVH, P < .0001) and mean charge during hospitalization (2019: $21 513, P < .0001) increased. Bronchiolitis patterns were similar. CONCLUSIONS: This study highlights the importance of ensuring access to RSV preventive measures for all infants.

Month of birth and height. A case study in rural Spain.

INTRODUCTION: Season of birth correlates to a wide range of health conditions throughout life measured by anthropometrics. This study explores whether the month of birth and weather during gestation influence male adult height, based on Spain's rural population before the end of the modernization process. METHODS: The database of heights (N = 16.266) is composed of conscripts who reached the age of 21 between 1908 and 1985 (birth cohorts 1886-1965). The population sample has been taken from a municipality in inner Spain: Hellín, in the region of Castilla-La Mancha, mainly an agrarian area, with poor resources and low income until the 1970 s/1980 s. Two different methodologies have been implemented: a harmonic regression using sinusoidal covariables and a random forest model. RESULTS: we find that being born at the end of the summer and during the autumn was favorable to height. The birth month with the highest statures is September, with heights 0.5 cm above the annual average and 0.9 cm above February, the birth month with the lowest average height. Furthermore, we can observe that rainfall and temperature during gestation had little additional influence due to a substitution effect with the birth month variable. CONCLUSIONS: Our results suggest that the seasonal effects on height can be significant and that it can be partially affected by environmental factors during early life. Our findings could be of interest for low-income populations and developing rural societies.

Birth month associated with tracheal colonization of Rhodococcus equi in newborn foals on horse-breeding farms with sporadic rhodococcosis in Japan.

Tracheal washing fluid was collected from 170 foals at 28 and 35 d old from February to July in a foaling season on horse-breeding farms with sporadic rhodococcosis in Japan and was investigated by quantitative culture. The history of the 170 foals followed up for the next few months. The proportion of R. equi-positive foals at 28 and 35 d old was significantly increased according to the birth month. Furthermore, the mean number of R. equi in the tracheal washing fluid of each month group increased according to their birth month with the rise in outside temperature. During the follow-up observation, 9/30 foals (30.0 %) born in February showed the first clinical signs at 56 ± 8 d old, 21/61 foals (34.4 %) born in March showed the signs at 37 ± 3 d old, 15/49 foals (30.6 %) born in April showed the signs at 39 ± 2 d old, and 7/30 foals (23.3 %) born in May showed signs at 44 ± 3 d old. Two sick foals (6.7 %) born in February, 19 sick foals (31.1 %) born in March, 15 sick foals (30.6 %) born in April, and 6 sick foals (20.0 %) born in May showed a positive culture of R. equi at 28 or 35 d old. The present study revealed that birth month is associated with the initial colonization of R. equi in the trachea of newborn foals on farms with sporadic rhodococcosis in Japan. Therefore, birth month might be a risk factor for developing R. equi pneumonia in foals.

Respiratory Syncytial Virus-Associated Hospital Admissions and Bed Days in Children <5 Years of Age in 7 European Countries.

BACKGROUND: Respiratory syncytial virus (RSV) is a leading cause of respiratory tract infections (RTIs) in young children. High-quality country-specific estimates of bed days and length of stay (LOS) show the population burden of RSV-RTI on secondary care services and the burden among patients, and can be used to inform RSV immunization implementation decisions. METHODS: We estimated the hospital burden of RSV-associated RTI (RSV-RTI) in children under 5 years in 7 European countries (Finland, Denmark, Norway, Scotland, England, the Netherlands, and Italy) using routinely collected hospital databases during 2001-2018. We described RSV-RTI admission rates during the first year of life by birth month and assessed their correlation with RSV seasonality in 5 of the countries (except for England and Italy). We estimated average annual numbers and rates of bed days for RSV-RTI and other-pathogen RTI, as well as the hospital LOS. RESULTS: We found that infants born 2 months before the peak month of RSV epidemics more frequently had the highest RSV-RTI hospital admission rate. RSV-RTI hospital episodes accounted for 9.9-21.2 bed days per 1000 children aged <5 years annually, with the median (interquartile range) LOS ranging from 2 days (0.5-4 days) to 4 days (2-6 days) between countries. Between 70% and 89% of these bed days were in infants aged <1 year, representing 40.3 (95% confidence interval [CI], 40.1-40.4) to 91.2 (95% CI, 90.6-91.8) bed days per 1000 infants annually. The number of bed days for RSV-RTI was higher than that for RTIs associated with other pathogens in infants aged <1 year, especially in those <6 months. CONCLUSIONS: RSV disease prevention therapies (monoclonal antibodies and maternal vaccines) for infants could help prevent a substantial number of bed days due to RSV-RTI. "High-risk" birth months should be considered when developing RSV immunization schedules. Variation in LOS between countries might reflect differences in hospital care practices.

Birth month and mortality in Japan: a population-based prospective cohort study.

Epidemiologic studies investigating the association between birth season and risk of mortality in adulthood are limited and have yielded inconclusive results. We aimed to examine the relationship between birth month and all-cause and cause-specific mortality, after controlling for potential confounders, including lifestyle and medical factors, in a population-based cohort study in Japan. We included 28,884 subjects (13,262 men and 15,622 women) from Takayama City, aged 35 years or older without cancer, stroke, and ischemic heart disease, who were born in Japan at baseline. Participants who were enrolled in 1992 were followed up for over 16 years. Information including place of birth, lifestyles, and medical history was obtained from a baseline questionnaire. We performed a Cox proportional hazards analysis to determine the association between birth month and all-cause and cause-specific mortality after adjusting for potential confounders. During the follow-up period (mean follow-up: 14.1 years), 5,303 deaths (2,881 men and 2,422 women) were identified. After controlling for multiple covariates, it was found that being born in April or June was associated with an increased risk of all-cause mortality compared to being born in January (hazard ratio [HR] 1.138; 95% confidence interval [CI], 1.006-1.288 and HR 1.169; 95% CI, 1.028-1.329, respectively). The HRs for cardiovascular mortality were significantly higher in participants born in March and May (HR 1.285; 95% CI, 1.056-1.565 and HR 1.293; 95% CI, 1.040-1.608, respectively). Our findings indicate that an individual's birth month may be an indicator of the susceptibility to mortality in later life.

Relative age and specific learning disorder diagnoses: A Finnish population-based cohort study.

Background: Being among the youngest in class has previously been associated with attention-deficit/hyperactivity disorder (ADHD) and academic disadvantage, but the relative age effect on learning disorders is less well understood. This study examined whether relatively young children are more likely to be diagnosed with specific learning disorders than their older peers. Methods: The setting included all 388,650 children born singleton in Finland from 1996 to 2002. Cases diagnosed with specific learning disorders in specialized health care by the age of 10 were identified from national registers. Cumulative incidences of specific learning disorders and the corresponding incidence rate ratios (IRRs) and 95% confidence intervals (CIs) were calculated for each birth month compared to January. Results: During follow-up, 3162 (0.8% of 388,650) children were diagnosed with a specific learning disorder. Children born in December displayed higher cumulative incidences for specific learning disorders than children born in January (IRR: 1.77, 95% CI: 1.50-2.11). The findings were similar for girls (IRR: 2.01, 1.44-2.83) and boys (IRR: 1.70, 1.39-2.08). ADHD did not explain the association, as the IRR for the youngest children with specific learning disorders and ADHD was 1.59 (1.13-2.26) compared to those without ADHD (IRR: 1.84, 1.51-2.24). Conclusions: Relatively younger children in Finnish schools were more likely to be diagnosed with a specific learning disorder by the age of 10. Increased awareness of how relative age differences affect the likelihood for children to be diagnosed with specific learning disorders is needed among parents, clinicians, and teachers.

Birth month and risk of skin tumors-Follow up of six million Caucasians born from 1950 to 2014 in Sweden.

BACKGROUND: Some studies hypothesize that birth month-as a proxy of exposure to ultraviolet radiation in early infancy-is associated with increased risk of skin tumors. METHODS: We studied a national cohort of all 5 874 607 individuals born in Sweden to parents of Swedish or Nordic origin as a proxy for Caucasian origin, 1950 to 2014. The cohort was followed for incident skin tumors, including squamous cell carcinomas and melanomas but not basal cell carcinomas, through 2015 from birth up to age 65 for the oldest cohort. Cox regression estimated the association between month of birth and risk of skin tumors in models adjusted for sex, calendar period, and education. Crude observed to expected ratios were also calculated. RESULTS: There were 33 914 cases of skin tumors, of these, 3025 were squamous cell cancer, 16 968 malignant melanoma and 8493 melanoma in situ/other and 5 428 squamous cell in situ/other in 192 840 593 person-years of follow-up. Observed to expected ratios by month of birth showed no association between month of birth and risk of skin tumors, and the same result was seen when Cox regression analysis was used. Subgroup analyses by sex, educational level, calendar period, or age at follow-up similarly showed no association. CONCLUSION: This large register-based cohort study showed no evidence of a higher risk of skin tumors in those born during the spring. Thus, this study lends no support to the hypothesis that birth during spring is a major risk factor for later skin tumors.

A large-scale study on the effect of age at first calving, dam parity, and birth and calving month on first-lactation milk yield in Holstein Friesian dairy cattle.

Milk yield during first lactation is an important economical trait. Age at first calving (AFC) is considered an important predictor of subsequent milk yield. In addition, both season of birth, as well as season of calving, have been shown to influence milk production, with conflicting results. Finally, higher parity of the dam has been associated with a lower performance of the offspring. The aim of the present study was to assess the effect of the above-mentioned factors based on a large-scale study and to rank the most important determinants for first-lactation milk yield. Data on 3,810,678 Holstein Friesian heifers, born in Belgium and the Netherlands between 2000 and 2015, were provided by Cooperative CRV and CRV BV (Arnhem, the Netherlands) and consisted of birth dates, calving dates, and first-lactation productions. In addition, herd, sire, and dam information was provided. Linear regression models were built with herd-calving year and sire as random effects and 305-d energy-corrected milk (ECM) yield during first lactation as outcome variable. Birth month, calving month, parity of the dam, and AFC were included as fixed effects in the model and a dominance analysis was performed to rank the associated factors according to importance. Results revealed AFC to be the most important factor (R2 = 0.047), with an increase in ECM up to an age of 33 mo. Calving month was a more important predictor than birth month (R2 = 0.010 vs. R2 = 0.002, respectively), with the highest first-lactation production in heifers calving in October to December, and the lowest in heifers calving in June and July. Birth month had a limited effect on first-lactation milk yield (R2 = 0.002), potentially masked by rearing strategies during early life. Finally, parity of the dam ≥3 was associated with a reduced ECM of the offspring (R2 = 0.002). In conclusion, our results show AFC to be an important determinant of milk yield during first lactation. In addition, seasonal patterns in milk production are seen, which should be further explored to identify the underlying mechanism.

Birth Month and Prevalence of Atopic Dermatitis in Children Under 3 Years in Antananarivo, Madagascar.

BACKGROUND: Several studies have been done to evaluate the relationship between month of birth and atopic diseases but the results are contradictory. OBJECTIVE: We aim to evaluate the correlation between the month of birth and the prevalence of AD in Malagasy children less than 3 years. METHODS: A case-control study was conducted based on patients' data of the department of Dermatology in the University Hospital Joseph Raseta Befelatanana (UH/JRB) Antananarivo. It included 438 children less than 3 years seen in this department between January 2010 and December 2019. For each atopic dermatitis (AD) patient, two age-and sex-matched controls without a history of AD were selected from the same period. RESULTS: This study included 146 AD cases and 292 non-AD controls. Our case-control study found that there is a statistically significant correlation between birth month and risk of AD in Malagasy children <3 years. Compared with people born in December, people born in April had the highest risk of AD (OR: 2.11, 95% CI 0.93-4.78), followed by people born in March (OR: 1.52, 95% CI 0.79-2,88). Asthma, allergic rhinitis and allergic conjunctivitis were significantly correlated with AD in our patients. CONCLUSION: Our case-control study found that being born in April and March (dry season) may be associated with an increased risk of AD.

The influence of birth month on total and cardiovascular mortality: a population-based surveillance study.

There is little evidence about the impact of birth month on total and cardiovascular disease mortality in developing countries. We evaluated these associations using the population health registration data of Hefei City, China from 2014 to 2017. After controlling for the fixed effects of gender, education, and occupation, we fitted the Cox proportional hazard regression model to assess the relationship between birth month and mortality. Hazard ratio (HR) with corresponding 95% confidence interval (CI) was calculated. All data analyses were performed by R 3.6.0 software. The data of 44 665 participants were analyzed in the study. Compared to people born in January, people born between May and October had higher total and cardiovascular mortality, being highest in June, respectively, HR: 1.130 (95%CI: 1.074 to 1.190) and HR: 1.200 (95%CI: 1.115 to 1.290). After stratification by gender, males born in June had highest risk total and cardiovascular mortality, with an increase in risk of 14.8% and 24.7%, respectively. For females, highest risk of total mortality was increased by 11.1% in those born in July, while those born in December had highest increase in cardiovascular mortality risk by 15.7%. Our results indicate in Hefei City, China month of birth is associated with total and cardiovascular disease mortality.

Birth month is associated with learning capacity in childhood in Northeast China.

It is difficult to evaluate long-term ventilation and indoor-outdoor temperature variation on-site in the birth residence so as to investigate their associations with learning capacity from childhood through adolescence. Here, we conducted a questionnaire-based retrospective cohort study in ten schools from two northeast China cities with warm summers and severe cold winters when residences had very low air exchange rates. Scores for Chinese, Mathematics, and English in the final exams of the summer semester in June 2018 were collected to evaluate learning capacity. We surveyed 6238 students aged 14.7 (SD: 2.1) years old. Using the 2nd quarter (April-May-June) birth as reference, 4th quarter (October-November-December) birth consistently was significantly associated with lower scores in Chinese in bivariate (ß, 95%CI: -3.2, -4.3 to -2.0) and multivariate (-1.8, -2.4 to -0.8) linear regression analyses. Stratified sub-analyses showed significant associations for male (-2.4, -3.7 to -1.1), urban (-2.4, -3.4 to -1.4), and primary students (-2.9, -4.5 to -1.4). Since household ventilation and indoor-outdoor temperature variation had great differences between the 2nd and 4th quarter of year, our results suggest that these two factors in the birth residence could be associated with learning capacity in childhood, especially for male and primary students in northeast China.

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

BACKGROUND: It 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. METHODS: We 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. RESULTS: We 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. CONCLUSIONS: The 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.

Birth month associates with risk of coronary artery disease and its complications: A propensity score matched analysis.

OBJECTIVE: Birth month and climate affect lifetime disease risk, while the underlying mechanisms remain largely elusive. It is vital to investigate the risks of coronary artery disease (CAD) and its complications in patients born in different months. METHODS: A total of 12,263 patient medical records were reviewed from the BioBank of First Affiliated Hospital of Xinxiang Medical University, with 4729 records from patients with CAD (CAD group) and 7534 records from control patients without CAD (control group). Two groups of patients were matched by the propensity score matched method. Birth months were compared between two groups of patients. The relationships between birth month and the numbers of CAD and its complications were also investigated. Interestingly, we also explore the relationship between the birth seasons and the numbers of CAD and its complications. RESULTS: Compared to control, CAD group had greater CAD risks for patients born in November (OR 1.390, 95% CI 1.090-1.772), December (OR 1.358, 95% CI 1.067-1.730), and February (OR 1.332, 95% CI 1.043-1.700) compared to those born in May. Compared to patients born in December, patients born in January to March and May to September had greater risk of heart failure (P<0.05). There was no difference in the incidence of myocardial infarction, conduction block, and atrial fibrillation across birth months (P>0.05). In terms of birth season, patients born in winter have greater CAD risk than those born in spring (OR 1.247, 95% CI 1.075-1.447). And there was no difference in the incidence of CAD complications across with birth seasons (P>0.05). CONCLUSIONS: There was a correlation between birth month and CAD. People born in November, December, and February had greater CAD risk, and people born in winter had greater CAD risk. Among CAD patients, those born in January to March and May to September had the greater risk of heart failure.

Seasonality of birth affects paediatric coeliac disease.

AIM: This study investigated the seasonality of birth in children diagnosed with coeliac disease (CD) at a tertiary University hospital in Southern Israel. METHODS: This was a population-based retrospective time series analysis study from January 1988 to December 2014. There were 308 903 live births at Soroka University Medical Centre during the study period and 699 were diagnosed with CD. We combined three databases covering births, CD diagnoses and weather indices. The daily proportion of births that resulted in CD for the different four seasons and high seasons were compared to the weather indices on the day of birth using negative binomial regression. RESULTS: Statistically significant associations were found between the season of birth and the rate of CD, with autumn births being associated with a higher risk for the development of CD than births during the summer, with an incidence ratio of 1.22. The association was further increased when the defined summer and autumn high seasons were used, with an incidence ratio of 1.40. No association was found between CD and the mean temperature and global radiation. CONCLUSION: Coeliac disease was associated with birth during the autumn and the autumn high season posed an even more significant risk factor.

Birth seasons and heights among girls and boys below 12 years of age: lasting effects and catch-up growth among native Amazonians in Bolivia.

BACKGROUND: Seasons affect many social, economic, and biological outcomes, particularly in low-resource settings, and some studies suggest that birth season affects child growth. AIM: To study a predictor of stunting that has received limited attention: birth season. SUBJECTS AND METHODS: This study uses cross-sectional data collected during 2008 in a low-resource society of horticulturists-foragers in the Bolivian Amazon, Tsimane'. It estimates the associations between birth months and height-for-age Z-scores (HAZ) for 562 girls and 546 boys separately, from birth until age 11 years or pre-puberty, which in this society occurs ∼13-14 years. RESULTS: Children born during the rainy season (February-May) were shorter, while children born during the end of the dry season and the start of the rainy season (August-November) were taller, both compared with their age-sex peers born during the rest of the year. The correlations of birth season with HAZ were stronger for boys than for girls. Controlling for birth season, there is some evidence of eventual partial catch-up growth, with the HAZ of girls or boys worsening until ∼ age 4-5 years, but improving thereafter. By age 6 years, many girls and boys had ceased to be stunted, irrespective of birth season. CONCLUSION: The results suggest that redressing stunting will require attention to conditions in utero, infancy and late childhood.