An analysis for paternal-age effect in Ohio's Down syndrome births, 1970-1980.

The purpose of this study was to analyze Down syndrome (DS) births during 1970-1980 in the State of Ohio for a paternal-age effect independent of maternal age. Birth certificates and chromosome analysis records were used to ascertain 1,244 white DS births, which by capture-recapture methodology were estimated to comprise two-thirds of all white DS births in Ohio for this period. The control data consisted of 1,667,210 white live births in Ohio during the same period. One method of statistical analysis was a case-control comparison, which for each single-year maternal age compares the mean paternal age for controls with each observed DS paternal age. No statistically significant paternal-age effect was found in nine of the 11 years. For two of the years, and for all years combined, the DS fathers were significantly younger than the fathers of controls. When the data were subdivided according to ascertainment, one subpopulation--those DS individuals obtained from birth certificates alone--also showed a statistically significant negative paternal-age effect. The Mantel-Haenszel test was also applied to these data. Assuming no paternal-age effect, a lower rate of DS births than expected was found at paternal ages greater than or equal to 40, but not at greater than or equal to 45, greater than or equal to 50, or greater than or equal to 55. These same methods were used to test for a maternal-age effect. In each of the 11 years and over all 11 years combined, a strong and statistically significant positive maternal-age effect was detected.     

Seasonal variation in conception and various pregnancy outcomes

Abstract

U.S. vital registration data on live births and data on abortions and ectopic pregnancies from a national hospital discharge survey were used to examine the seasonality of conceptions and the influence the conception pattern has on the monthly incidence of abortions and ectopic pregnancies. We found that in the United States conceptions follow a consistent seasonal pattern with the peak in November and December. However, when the pattern for conceptions is controlled, the monthly variation for abortions and ectopic pregnancies is not significant. Therefore, we find no monthly excess for any of these outcomes of pregnancy over that expected as a consequence of the seasonality of conception. We suggest the monthly variation for the number of each of these pregnancy outcomes will best be explained when the seasonal variation in conceptions is understood.     

Heliogeophysical correlates of early biodemographic variables in the South of Western Siberia

In order to verify associations between solar and geomagnetic activities and perinatal variables, the monthly distributions of population characters in Novosibirsk Region over the period 1980–2001 were compared by stepwise correlation analysis with monthly averaged physical parameters at lags from 0 to 10 months. The three indices were: number of sunspots, solar flux at 10.7 cm wavelength, and A _k index measured at a local ionospheric station near the city of Novosibirsk. Official data on the numbers of single and multiple live births, stillbirths and infant deaths at the age under one year indicating the type of population and gender were provided by the State Statistical Committee. All three physical parameters positively correlated with the number of single births and infant mortality rate and negatively with twin births in urban and in rural populations, irrespective of lags. The direct association between A _k and the relative number of stillbirths in urban setting was mostly pronounced at a lag of 5 months. The number of live births increased along with A _k owing to the enhanced proportion of girls born, whereas the number of stillbirths after the rise in solar and geomagnetic activities increased because of boy deaths.     

Disentangling the Effects of Risk Factors and Clinical Care on Subnational Variation in Early Neonatal Mortality in the United States

Objective

Between 1990 and 2010, the U.S ranking in neonatal mortality slipped from 29^th to 45^th among countries globally. Substantial subnational variation in newborn mortality also exists. Our objective is to measure the extent to which trends and subnational variation in early neonatal mortality reflect differences in the prevalence of risk factors (gestational age and birth weight) compared to differences in clinical care.

Methods

Observational study using linked birth and death data for all births in the United States between 1996 and 2006. We examined health service area (HSA) level variation in the expected early neonatal mortality rate, based on gestational age (GA) and birth-weight (BW), and GA-BW adjusted mortality as a proxy for clinical care. We analyzed the relationship between selected health system indicators and GA-BW-adjusted mortality.

Results

The early neonatal death (ENND) rate declined 12% between 1996 and 2006 (2.39 to 2.10 per 1000 live births). This occurred despite increases in risk factor prevalence. There was significant HSA-level variation in the expected ENND rate (Rate Ratio: 0.73–1.47) and the GA-BW adjusted rate (Rate ratio: 0.63–1.68). Accounting for preterm volume (defined as <34 weeks), the number of neonatologist and NICU beds, 25.2% and 58.7% of the HSA-level variance in outcomes was explained among all births and very low birth weight babies, respectively.

Conclusion

Improvements in mortality could be realized through the expansion or reallocation of clinical neonatal resources, particularly in HSAs with a high volume of preterm births; however, prevention of preterm births and low-birth weight babies has a greater potential to improve newborn survival in the United States.     

Down syndrome rates and relaxed selection at older maternal ages.

Preferential survival in older mothers of fetuses with Down syndrome has been proposed as contributing to the maternal-age effect of this condition. If correct, this provocative hypothesis, which may be termed "relaxed selection," has major implications for approaches to prevention of Down syndrome live births in older women. Several predictions of this hypothesis are examined here by comparisons of parental ages among various populations. These revealed that: (1) mean maternal age of Down syndrome live births is slightly lower than that of Down syndrome spontaneous fetal deaths; (2) mean maternal age of those with mutant D/21 translocation Down syndrome is about the same as that of controls; (3) the ages of Down syndrome mothers who have Down syndrome live births is slightly lower than ages of Down syndrome mothers who have unaffected live births; and (4) in recent data on 47, +21 cases in which the extra chromosome 21 is of paternal origin, the mean maternal ages are 4-5 years lower than the maternal ages of cases of maternal origin (in contrast to earlier reports). All of these observations are contrary to the hypothesis that relaxed selection contributes significantly to the maternal-age association of Down syndrome. If there is any effect of relaxed selection, it is likely to be very weak and/or act primarily upon abortions that occur before recognition of pregnancy.     

Epidemiological features of infantile hypertrophic pyloric stenosis in Taiwanese children: a Nation-Wide Analysis of Cases during 1997-2007

Objective

To describe the epidemiological characteristics of infantile hypertrophic pyloric stenosis (IHPS) in ethnic Chinese children.

Materials and Methods

We reviewed the National Health Insurance claims database and analyzed data from children less than one year of age who had been diagnosed with IHPS (ICD-9-CM 750.5) and had undergone pyloromyotomy (ICD-9-CM 43.3). We analyzed the incidence, gender, age at diagnosis, length of hospital stay, seasonal variation and cost of IHPS from data collected between January 1997 and December 2007.

Results

A total of 1,077 infants met inclusion criteria, including 889 boys and 188 girls. The annual incidence of IHPS ranged from 0.30 to 0.47 per 1,000 live births with a mean incidence of 0.39 per 1,000 live births. Between 2002 and 2007, the incidence showed a declining trend (P = 0.025) with coincidentally increasing trends for both exclusive breastfeeding (P = 0.014) and breastfeeding plus bottle feeding (P = 0.004). The male-to-female rate ratio was dynamic and increased from 3.03 during the first two weeks of life to 8.94 during the 8^th through 10^thweeks of life. The overall male-to-female rate ratio was 4.30. The mean age at diagnosis was 43.1±2.4 days. After analyzing the months of birth and hospital admission, no seasonal variation associated with IHPS was detected. The mean length of hospital stay was 8.28±7.10 days.

Conclusions

The incidence of IHPS in Taiwan, a country with a majority ethnic Chinese population, was lower than observed incidences in Caucasian populations living in Western countries. Breastfeeding campaigns and low maternal smoking rates may contribute to the lower incidence of IHPS in Taiwan. However, additional studies with longer follow-up periods are needed.     

Recent trends in infant mortality rates and proportions of low-birth-weight live births in Canada

OBJECTIVE: To identify spatial patterns of changes in infant mortality rates and proportions of low-birth-weight live births observed in 1994. SETTING: Canada. SUBJECTS: Live births and infant deaths in Canada between 1987 and 1994. Data for Newfoundland were unavailable for 1987 through 1990. OUTCOME MEASURES: Annual infant mortality rates (crude and after excluding live newborns weighing less than 500 g); proportion of live births by low-birth-weight category (500-2499 g). RESULTS: Nova Scotia, New Brunswick, Quebec and Manitoba had lower crude and adjusted infant mortality rates in 1994 than in 1993. Newfoundland, Saskatchewan, Alberta and British Columbia had higher rates in 1994 than in 1993. The crude rate in Ontario was lower, and the adjusted rate higher, in 1994 than in 1993. A downward trend in the proportion of low-birth-weight live births was observed in Quebec (chi(2) for trend = 29.2, p < 0.01). Conversely, an upward trend was observed in Ontario (chi(2) for trend = 241.3, p < 0.01). However, the increase may have been due to data errors, especially in 1993 and 1994, involving truncation of ounces in 2 digits to 1 digit (e.g., 5 pounds 10 ounces became 5 pounds 1 ounce). CONCLUSIONS: Although the marginal increases in infant mortality observed in several provinces could be the result of random variation, future trends should be closely monitored. The proportion of low-birth-weight live births in Canada (excluding Ontario) appears to be stable, with Quebec showing significant reductions. The errors in data for Ontario need to be corrected before trends can be estimated for that province and for Canada as a whole.     

Sources of Variation in the Ampicillin-Resistant Escherichia coli Concentration in the Feces of Organic Broiler Chickens

Currently, there are limited published data for the population dynamics of antimicrobial-resistant commensal bacteria. This study was designed to evaluate both the proportions of the Escherichia coli populations that are resistant to ampicillin at the level of the individual chicken on commercial broiler farms and the feasibility of obtaining repeated measures of fecal E. coli concentrations. Short-term temporal variation in the concentration of fecal E. coli was investigated, and a preliminary assessment was made of potential factors involved in the shedding of high numbers of ampicillin-resistant E. coli by growing birds in the absence of the use of antimicrobial drugs. Multilevel linear regression modeling revealed that the largest component of random variation in log-transformed fecal E. coli concentrations was seen between sampling occasions for individual birds. The incorporation of fixed effects into the model demonstrated that the older, heavier birds in the study were significantly more likely (P = 0.0003) to shed higher numbers of ampicillin-resistant E. coli. This association between increasing weight and high shedding was not seen for the total fecal E. coli population (P = 0.71). This implies that, in the absence of the administration of antimicrobial drugs, the proportion of fecal E. coli that was resistant to ampicillin increased as the birds grew. This study has shown that it is possible to collect quantitative microbiological data on broiler farms and that such data could make valuable contributions to risk assessments concerning the transfer of resistant bacteria between animal and human populations.     

Methylenetetrahydrofolate reductase polymorphism is not risk factor for Down syndrome in North India

BACKGROUND:

Down syndrome (DS) is the most common cause of mental retardation of genetic etiology with the prevalence rate of 1/700 to 1/1000 live births worldwide. Several polymorphisms in folate/homocysteine metabolism pathways genes have been reported as a risk factor in women for bearing DS child, but very few studies investigated these polymorphisms in DS cases whether there are a risk factor for being DS or not.

OBJECTIVE:

We have investigated the association of methylenetetrahydrofolate reductase (MTHFR) with the occurrence of DS in Indian population. MTHFR is one of the key regulatory enzymes involved in the metabolic pathway of homocysteine responsible for the reduction of methyltetrahydrofolate. A total of 32 DS cases and 64 age, sex matched controls were genotyped for MTHFR C677T polymorphism by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS:

The observed genotype frequencies were CC = 0.81; CT = 0.17 and TT = 0.02 in controls and CC = 0.81 and CT = 0.19 in DS cases. Frequency of T allele in DS and controls were 0.09 and 0.1, respectively. Significant difference in the distribution of mutant 677T allele was not observed between DS cases and controls (odds ratio = 0.915; 95% confidence intervals: 0.331-2.53; P = 0.864).

CONCLUSION:

Results of this study indicate that MTHFR C677T polymorphism is not risk factor for DS.     

Birth seasonally among peasant cultivators: The interrelationship of workload,diet, and fertility

The monthly distribution of live births was analyzed over a 51-year period, 1926–1976, for a rural Taiwan fishing community. Unlike previous studies of birth seasonality, monthly distributions of births did not deviate from what would be expected by chance. This new case is shown to be consistent with the suggestion, developed by Pasternak during a study of birth seasonality in two Taiwan farming communities, that for peasant cultivators the annual cycle of production exerts a more decisive influence on birth seasonality than time of marriage or attributes of temperature, rainfall, or workload. An hypothesis that links the productive cycle to conceptions through the intervening variable of diet is presented and successfully tested using several sets of data on monthly births. A direct effect of nutrition on human fertility, suggested by recent studies of reproductive performance under conditions of nutritional stress, may largely explain seasonality of conceptions and births in populations that experience significant seasonal variation in diet.The Cross Harbor data presented in this paper were collected as part of an ongoing investigation of the comparative demography and social structure of fishing, farming, and market town communities located within a particular Chinese regional system. The support of the National Science Foundation during the period of fieldwork is gratefully acknowledged. I wish to thank G. William Skinner, William H. Durham, Greg Acciaioli, Steven Sangren, Chuang Miao-huei, Harumi Befu, and Philip L. Ritter for their comments on earlier drafts of the present article. I owe a special debt of gratitude to Burton Pasternak (City University of New York), who intellectually inspired and personally encouraged the writing of this paper.     

Venous Thromboembolism in an Industrial North American City: Temporal Distribution and Association with Particulate Matter Air Pollution

Background

Emerging evidence, mainly from Europe and Asia, indicates that venous thromboembolism (VTE) occurs most often in winter. Factors implicated in such seasonality are low temperature-mediated exacerbation of coagulation and high levels of particulate matter (PM) air pollution. However, in contrast to most European and Asian cities, particulate matter pollution peaks in the summer in many North American cities.

Objectives

We aimed to exploit this geographical difference and examine the temporal distribution of VTE in a cold-weather, North American city, Detroit, with a summer PM peak. Our goal was thereby to resolve the influence of temperature and PM levels on VTE.

Methods

Our retrospective, analytical semi-ecological study used chart review to confirm 1,907 acute, ambulatory VTE cases, divided them by location (Detroit versus suburban), and plotted monthly VTE frequency distributions. We used Environmental Protection Agency data to determine the temporal distribution of PM pollution components in Detroit. Suburban PM air pollution is presumed negligible and therefore not monitored.

Results

Acute VTE cases in Detroit (1,490) exhibited a summer peak (June 24^th) and differed from both a uniform distribution (P<0.01) and also that of 1,123 no-VTE cases (P<0.02). Levels of 10 µm diameter PM and coarse particle (2.5 to 10 µm) PM also exhibited summer peaks versus a winter peak for 2.5 µm diameter PM. Contrary to their urban counterparts, suburban cases of acute VTE (417) showed no monthly variation.

Conclusions

The summer peak of acute VTE in Detroit indicates that low temperature is not a major factor in VTE pathogenesis. In contrast, concordance of the 10 µm diameter PM, coarse particle, and the Detroit VTE monthly distributions, combined with no monthly suburban VTE variation, is consistent with a role for PM pollution. Furthermore, divergence of the VTE and 2.5 µm PM distributions suggests that particle size may play a role.     

Family-Based Association Analysis Confirms the Role of the Chromosome 9q21.32 Locus in the Susceptibility of Diabetic Nephropathy

A genome-wide association scan of type 1 diabetic patients from the GoKinD collections previously identified four novel diabetic nephropathy susceptibility loci that have subsequently been shown to be associated with diabetic nephropathy in unrelated patients with type 2 diabetes. To expand these findings, we examined whether single nucleotide polymorphisms (SNPs) at these susceptibility loci were associated with diabetic nephropathy in patients from the Joslin Study of Genetics of Nephropathy in Type 2 Diabetes Family Collection. Six SNPs across the four loci identified in the GoKinD collections and 7 haplotype tagging SNPs, were genotyped in 66 extended families of European ancestry. Pedigrees from this collection contained an average of 18.5 members, including 2 to 14 members with type 2 diabetes. Among diabetic family members, the 9q21.32 locus approached statistical significance with advanced diabetic nephropathy (P = 0.037 [adjusted P = 0.222]). When we expanded our definition of diabetic nephropathy to include individuals with high microalbuminuria, the strength of this association improved significantly (P = 1.42×10⁻³ [adjusted P = 0.009]). This same locus also trended toward statistical significance with variation in urinary albumin excretion in family members with type 2 diabetes (P = 0.032 [adjusted P = 0.192]) and in analyses expanded to include all relatives (P = 0.019 [adjusted P = 0.114]). These data increase support that SNPs identified in the GoKinD collections on chromosome 9q21.32 are true diabetic nephropathy susceptibility loci.     

Barn Owl Productivity Response to Variability of Vole Populations

We studied the response of the barn owl annual productivity to the common vole population numbers and variability to test the effects of environmental stochasticity on their life histories. Current theory predicts that temporal environmental variability can affect long-term nonlinear responses (e.g., production of young) both positively and negatively, depending on the shape of the relationship between the response and environmental variables. At the level of the Czech Republic, we examined the shape of the relationship between the annual sum of fledglings (annual productivity) and vole numbers in both non-detrended and detrended data. At the districts’ level, we explored whether the degree of synchrony (measured by the correlation coefficient) and the strength of the productivity response increase (measured by the regression coefficient) in areas with higher vole population variability measured by the s-index. We found that the owls’ annual productivity increased linearly with vole numbers in the Czech Republic. Furthermore, based on district data, we also found that synchrony between dynamics in owls’ reproductive output and vole numbers increased with vole population variability. However, the strength of the response was not affected by the vole population variability. Additionally, we have shown that detrending remarkably increases the Taylor’s exponent b relating variance to mean in vole time series, thereby reversing the relationship between the coefficient of variation and the mean. This shift was not responsible for the increased synchrony with vole population variability. Instead, we suggest that higher synchrony could result from high food specialization of owls on the common vole in areas with highly fluctuating vole populations.     

Associations between cesarean delivery and child mortality: A national record linkage longitudinal study of 17.8 million births in Brazil

BackgroundThere is an increasing use of cesarean delivery (CD) based on preference rather than on medical indication. However, the extent to which nonmedically indicated CD benefits or harms child survival remains unclear. Our hypothesis was that in groups with a low indication for CD, this procedure would be associated with higher child mortality and in groups with a clear medical indication CD would be associated with improved child survival chances.Methods and findingsWe conducted a population-based cohort study in Brazil by linking routine data on live births between January 1, 2012 and December 31, 2018 and assessing mortality up to 5 years of age. Women with a live birth who contributed records during this period were classified into one of 10 Robson groups based on their pregnancy and delivery characteristics. We used propensity scores to match CD with vaginal deliveries (1:1) and prelabor CD with unscheduled CD (1:1) and estimated associations with child mortality using Cox regressions. A total of 17,838,115 live births were analyzed. After propensity score matching (PSM), we found that live births to women in groups with low expected frequencies of CD (Robson groups 1 to 4) had a higher death rate up to age 5 years if they were born via CD compared with vaginal deliveries (HR = 1.25, 95% CI: 1.22 to 1.28; p < 0.001). The relative rate was greatest in the neonatal period (HR = 1.39, 95% CI: 1.34 to 1.45; p < 0.001). There was no difference in mortality rate when comparing offspring born by a prelabor CD to those born by unscheduled CD. For the live births to women with a CD in a prior pregnancy (Robson group 5), the relative rates for child mortality were similar for those born by CD compared with vaginal deliveries (HR = 1.05, 95% CI: 1.00 to 1.10; p = 0.024). In contrast, for live births to women in groups with high expected rates of CD (Robson groups 6 to 10), the child mortality rate was lower for CD than for vaginal deliveries (HR = 0.90, 95% CI: 0.89 to 0.91; p < 0.001), particularly in the neonatal period (HR = 0.84, 95% CI: 0.83 to 0.85; p < 0.001). Our results should be interpreted with caution in clinical practice, since relevant clinical data on CD indication were not available.ConclusionsIn this study, we observed that in Robson groups with low expected frequencies of CD, this procedure was associated with a 25% increase in child mortality. However, in groups with high expected frequencies of CD, the findings suggest that clinically indicated CD is associated with a reduction in child mortality.

In a study of linked population-based data, Enny Paixao and colleagues study the associations between cesarean section and child mortality among 17.8 million live births in Brazil.     

Chromosome aberration and environmental physical activity: Down syndrome and solar and cosmic ray activity, Israel, 1990–2000

The possibility that environmental effects are associated with chromosome aberrations and various congenital pathologies has been discussed previously. Recent advances in the collection and computerization of data make studying these potential associations more feasible. The aim of this study was to investigate a possible link between the number of Down syndrome (DS) cases detected prenatally or at birth yearly in Israel over a 10-year period compared with the levels of solar and cosmic ray activity 1 year before the detection or birth of each affected child. Information about 1,108,449 births was collected for the years 1990–2000, excluding 1991, when data were unavailable. A total of 1,310 cases of DS were detected prenatally or at birth—138 in the non-Jewish community and 1,172 in the Jewish population. Solar activity indices—sunspot number and solar radio flux 2,800 MHz at 10.7 cm wavelength for 1989–1999—were compared with the number of DS cases detected. Pearson correlation coefficients (r) and their probabilities (P) were established for the percentage of DS cases in the whole population. There was a significant inverse correlation between the indices of solar activity and the number of cases of DS detected—r=–0.78, P=0.008 for sunspot number and r=–0.76, P=0.01 for solar flux. The possibility that cosmophysical factors inversely related to solar activity play a role in the pathogenesis of chromosome aberrations should be considered. We have confirmed a strong trend towards an association between the cosmic ray activity level and the incidence of DS.     

Annual Variation in Ecology and Reproduction of Wild Simakobu (Simias concolor)

Seasonal breeding in primates is related to the degree of environmental seasonality, particularly the availability and predictability of food. Southeast Asian species in general show moderate birth seasonality due to either low environmental seasonality or unpredictable fluctuations of mast-fruiting food resources. One Southeast Asian primate, the simakobu (Simias concolor), however, has been reported to be a strict seasonal breeder with births occurring in June and July only. It is unclear whether these observations are characteristic of the species or result from a sampling bias. To address this question, we documented the annual distribution of 11 births in eight groups of simakobu over two consecutive years at Pungut, an undisturbed site on Siberut Island, Indonesia. We assessed annual variation in ecology and reproduction via rainfall, temperature, food availability, feeding time, physical condition, conceptions, and births. Mean monthly temperature was nearly constant (26.3–27.1?°C), and monthly precipitation always high (219–432?mm). Although simakobu foods were abundant year-round, there were two fruit-feeding peaks in June and September. In contrast to previous reports, we documented births in 7?mo. Most births occurred in October (45?%), the wettest month of the year, and most conceptions in March and April, following a peak in unripe fruit availability. Although sample sizes are very small, females seemed to conceive when their physical condition was best, suggesting that simakobu time conceptions flexibly to the recovery of energy reserves. Across study sites, births occurred in 10 calendar months, indicating that simakobu reproduction is not strictly seasonal.     

Parity and the Risk of Diabetes Mellitus among Chinese Women: A Cross-Sectional Evidence from the Tongji-Dongfeng Cohort Study

Objectives

Little is known about the long-term health impact of pregnancy on women. The objective of this study was to examine the association between parity and the risk of diabetes among a population of Chinese women.

Study design

A total of 14,196 women (aged ≥45 years) from the Dongfeng-Tongji Cohort study who had experienced at least one live birth completed baseline questionnaires, medical examinations, and provided baseline blood samples. Participants were categorized into four groups according to parity (one, two, three, or four or more live births). Logistic regression models were used to investigate the association between parity and the risk of diabetes after controlling potential confounders.

Results

The prevalence of diabetes in the study population was 18.0% (2,552/14,196). Fasting plasma glucose levels increased with the increasing number of live births (P<0.001) and parity had a positive graded association with diabetes without adjustment for any covariates (P for trend <0.001). After adjusting for potential confounders, women who had had two, three, and four or more live births had 1.35 times (95% CI, 1.20–1.52), 1.59 times (95% CI, 1.39–1.82) and 1.44 times (95% CI, 1.21–1.71), respectively, higher risk of diabetes compared with women who had had one live birth.

Conclusion

Multiparity was associated with increasing risk of diabetes in this population of Chinese women. These findings suggested that multiparity may be a risk factor for the development of diabetes among Chinese women. Future studies are needed to examine the physiological changes during pregnancy for risk of diabetes in later life.     

Whatever the weather: ambient temperature does not influence the proportion of males born in New Zealand

Background

The proportion of male births has been shown to be over 50% in temperate climates around the world. Given that fluctuations in ambient temperature have previously been shown to affect sex allocation in humans, we examined the hypothesis that ambient temperature predicts fluctuations in the proportion of male births in New Zealand.

Methodology/Principal Findings

We tested three main hypotheses using time series analyses. Firstly, we used historical annual data in New Zealand spanning 1876–2009 to test for a positive effect of ambient temperature on the proportion of male births. The proportion of males born ranged by 3.17%, from 0.504 to 0.520, but no significant relationship was observed between male birth rates and mean annual temperature in the concurrent or previous years. Secondly, we examined whether changes in annual ambient temperature were negatively related to the proportion of male stillbirths from 1929–2009 and whether the proportion of male stillbirths negatively affected the proportion of male live births. We found no evidence that fewer male stillbirths occurred during warmer concurrent or previous years, though a declining trend in the proportion of male stillbirths was observed throughout the data. Thirdly, we tested whether seasonal ambient temperatures, or deviations from those seasonal patterns, were positively related to the proportion of male births using monthly data from 1980–2009. Patterns of male and female births are seasonal, but very similar throughout the year, resulting in a non-seasonal proportion of male births. However, no cross correlations between proportion of male births and lags of temperature were significant.

Conclusions

Results showed, across all hypotheses under examination, that ambient temperatures were not related to the proportion of male births or the proportion of male stillbirths in New Zealand. While there is evidence that temperature may influence human sex allocation elsewhere, such effects of temperature are not universal.     

A Population Based Study of Seasonality of Skin and Soft Tissue Infections: Implications for the Spread of CA-MRSA

Methicillin resistant Staphylococcus aureus (MRSA) is currently a major cause of skin and soft tissue infections (SSTI) in the United States. Seasonal variation of MRSA infections in hospital settings has been widely observed. However, systematic time-series analysis of incidence data is desirable to understand the seasonality of community acquired (CA)-MRSA infections at the population level. In this paper, using data on monthly SSTI incidence in children aged 0–19 years and enrolled in Medicaid in Maricopa County, Arizona, from January 2005 to December 2008, we carried out time-series and nonlinear regression analysis to determine the periodicity, trend, and peak timing in SSTI incidence in children at different age: 0–4 years, 5–9 years, 10–14 years, and 15–19 years. We also assessed the temporal correlation between SSTI incidence and meteorological variables including average temperature and humidity. Our analysis revealed a strong annual seasonal pattern of SSTI incidence with peak occurring in early September. This pattern was consistent across age groups. Moreover, SSTIs followed a significantly increasing trend over the 4-year study period with annual incidence increasing from 3.36% to 5.55% in our pediatric population of approximately 290,000. We also found a significant correlation between the temporal variation in SSTI incidence and mean temperature and specific humidity. Our findings could have potential implications on prevention and control efforts against CA-MRSA.