Month of birth and offspring count of women: data from the Southern hemisphere

Detecting month and year of birth effects on reproduction and marriage patterns in two long-term data sets

This study examines the effects of birth month on reproduction and mating behavior using historical and contemporary census data from 1820 to 1970. The research examines the effect of birth month on the number of children for women and their male spouses, finding a monthly cycle for both men and women. In addition, the study examines whether birth month influences whether a person has ever been married. In support of previous research, we find clear birth month effects on the number of children for both women and their spouses, while the time series of ever being married shows a 60-month and a 10-year cycle, the latter possibly related to the solar cycle. Although the effects are small, both results, based on a large and representative dataset, indicate the importance of early life factors on mating and reproduction.

Assessment of effects of moon phases on hospital outpatient visits: An observational national study

Objectives

A vast amount of literature has been conducted for investigating the association of different lunar phases with human health; and it has mixed reviews for association and non-association of diseases with lunar phases. This study investigates the existence of any impact of moon phases on humans by exploring the difference in the rate of outpatient visits and type of diseases that prevail in either non-moon or moon phases.

Methods

We retrieved dates of non-moon and moon phases for eight years (1st January 2001-31st December 2008) from the timeanddate.com website for Taiwan. The study cohort consisted of 1 million people from Taiwan's National Health Insurance Research Database (NHIRD) followed over eight years (1st January 2001-31st December 2008). We used the two-tailed, paired-t-test to compare the significance of difference among outpatient visits for 1229 moon phase days and 1074 non-moon phase days by using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes from NHIRD records.

Results

We found 58 diseases that showed statistical differences in number of outpatient visits in the non-moon and moon phases.

Conclusions

The results of our study identified diseases that have significant variations during different lunar phases (non-moon and moon phases) for outpatient visits in the hospital. In order to fully understand the reality of the pervasive myth of lunar effects on human health, behaviors and diseases, more in-depth research investigations are required for providing comprehensive evidence covering all the factors, such as biological, psychological and environmental aspects.

Impact of Environmental Pollution on Female Reproduction

The increased pollution in the world atmosphere is a global concern. Water, air, and soil are polluted by various sources, such as farm fertilizer, sewage industrial waste products, fumes, and plastics, which in turn impact human health. Plastics and other mixtures of waste affect live in the water. Moreover, the ecosystem is disrupted by the use of heavy metal-containing chemicals in agriculture, and those are eventually consumed by humans. The consequences are a significant negative impact on health including reproductive health, which impairs fertility in the human population. Reproductive functions are severely affected by different chemicals which may interfere with hormonal functions. Greater consequences are faced by the women as the number of germ cells present in the ovary is fixed during fetal life, and which are nonrenewable. From the production of ovum to fertilization, to implantation, and finally continuation of pregnancy, all are affected by the heavy metals and endocrine disruptors. Lifestyle modifications such as consumption of organic foods, plastic product avoidance, separation of residential areas from industrial/agricultural areas, proper waste disposal, and so on, may help to improve the situation.

Female Reproductive Performance and Maternal Birth Month: A Comprehensive Meta-Analysis Exploring Multiple Seasonal Mechanisms

Globally, maternal birth season affects fertility later in life. The purpose of this systematic literature review is to comprehensively investigate the birth season and female fertility relationship. Using PubMed, we identified a set of 282 relevant fertility/birth season papers published between 1972 and 2018. We screened all 282 studies and removed 131 non-mammalian species studies on fertility and 122 studies that were on non-human mammals. Our meta-analysis focused on the remaining 29 human studies, including twelve human datasets from around the world (USA, Europe, Asia). The main outcome was change in female fertility as observed by maternal birth month and whether this change was correlated with either temperature or rainfall. We found that temperature was either strongly correlated or anti-correlated in studies, indicating that another factor closely tied to temperature may be the culprit exposure. We found that rainfall only increases fertility in higher altitude locations (New Zealand, Romania, and Northern Vietnam). This suggests the possibility of a combined or multi-factorial mechanism underlying the female fertility - birth season relationship. We discuss other environmental and sociological factors on the birth season - female fertility relationship. Future research should focus on the role of birth season and female fertility adjusting for additional factors that modulate female fertility as discussed in this comprehensive review.

A model investigating environmental factors that play a role in female fecundity or birth rate

OBJECTIVE

Over 12% of women in the United States have reduced fertility and/or fecundity. Environmental factors, such as temperature, and socioeconomic factors have been implicated in reducing female fecundity. The purpose of this study is to investigate the effect of environmental factors coupled with socioeconomic factors on birth rate at the country-level. We use birth rate as a proxy for female fecundity. This will enable us to identify the most important factors affecting female fecundity.

METHODS

Using country-specific data from 182 countries, we constructed a regression model of the effects of environmental and socioeconomic factors on birth rate at the country-level. Our model assesses the role of temperature, Gross Domestic Product (GDP) per capita, fine air particulate matter (PM 2.5), and prevalence of male and female Body Mass Index (BMI) > = 25 (age-standardized) on birth rate per country. Because many of these factors are inter-dependent, we include all possible two-way interaction terms to assess the role of individual factors and interactions between multiple factors in the model.

RESULTS

In the full regression model, we found that GDP per capita along with 5 interaction terms were significant after adjusting for multiple testing. Female BMI was only nominally significant. GDP per capita was independently associated with birth rate (adjusted p-value <0.001). Prevalence of BMI > = 25 age-standardized in males and females were also significant when interacting with air pollution or GDP on female fecundity (birth rate). Temperature did not affect birth rate either independently or as an interaction unless BMI was removed from the model.

CONCLUSION

A country's economic wealth was the most significant factor in predicting birth rate in a statistical model that includes environmental and socioeconomic variables. This is important for future studies investigating environmental factors involved in increasing or decreasing female fecundity.

Modeling month-season of birth as a risk factor in mouse models of chronic disease: from multiple sclerosis to autoimmune encephalomyelitis

Month-season of birth (M-SOB) is a risk factor in multiple chronic diseases, including multiple sclerosis (MS), where the lowest and greatest risk of developing MS coincide with the lowest and highest birth rates, respectively. To determine whether M-SOB effects in such chronic diseases as MS can be experimentally modeled, we examined the effect of M-SOB on susceptibility of C57BL/6J mice to experimental autoimmune encephalomyelitis (EAE). As in MS, mice that were born during the M-SOB with the lowest birth rate were less susceptible to EAE than mice born during the M-SOB with the highest birth rate. We also show that the M-SOB effect on EAE susceptibility is associated with differential production of multiple cytokines/chemokines by neuroantigen-specific T cells that are known to play a role in EAE pathogenesis. Taken together, these results support the existence of an M-SOB effect that may reflect seasonally dependent developmental differences in adaptive immune responses to self-antigens independent of external stimuli, including exposure to sunlight and vitamin D. Moreover, our documentation of an M-SOB effect on EAE susceptibility in mice allows for modeling and detailed analysis of mechanisms that underlie the M-SOB effect in not only MS but in numerous other diseases in which M-SOB impacts susceptibility.-Reynolds, J. D., Case, L. K., Krementsov, D. N., Raza, A., Bartiss, R., Teuscher, C. Modeling month-season of birth as a risk factor in mouse models of chronic disease: from multiple sclerosis to autoimmune encephalomyelitis.

Birth month affects lifetime disease risk: a phenome-wide method

OBJECTIVE

An individual's birth month has a significant impact on the diseases they develop during their lifetime. Previous studies reveal relationships between birth month and several diseases including atherothrombosis, asthma, attention deficit hyperactivity disorder, and myopia, leaving most diseases completely unexplored. This retrospective population study systematically explores the relationship between seasonal affects at birth and lifetime disease risk for 1688 conditions.

METHODS

We developed a hypothesis-free method that minimizes publication and disease selection biases by systematically investigating disease-birth month patterns across all conditions. Our dataset includes 1 749 400 individuals with records at New York-Presbyterian/Columbia University Medical Center born between 1900 and 2000 inclusive. We modeled associations between birth month and 1688 diseases using logistic regression. Significance was tested using a chi-squared test with multiplicity correction.

RESULTS

We found 55 diseases that were significantly dependent on birth month. Of these 19 were previously reported in the literature (P < .001), 20 were for conditions with close relationships to those reported, and 16 were previously unreported. We found distinct incidence patterns across disease categories.

CONCLUSIONS

Lifetime disease risk is affected by birth month. Seasonally dependent early developmental mechanisms may play a role in increasing lifetime risk of disease.

Early life exposure to undernutrition induces ER stress, apoptosis, and reduced vascularization in ovaries of adult rat offspring

Maternal nutritional restriction has been shown to induce impairments in a number of organ systems including the ovary. We have previously shown that maternal undernutrition induces fetal growth restriction and low birth weight, and results in an offspring ovarian phenotype characteristic of premature ovarian aging with reduced ovarian reserve. In the present study, we set out to investigate the underlying mechanisms that lead offspring of undernourished mothers to premature ovarian aging. Pregnant dams were randomized to 1) a standard diet throughout pregnancy and lactation (control), 2) a calorie-restricted (50% of control) diet during pregnancy, 3) a calorie-restricted (50% of control) diet during pregnancy and lactation, or 4) a calorie-restricted (50% of control) diet during lactation alone. The present study shows that early life undernutrition-induced reduction of adult ovarian follicles may be mediated by increased ovarian endoplasmic reticulum stress in a manner that increased follicular apoptosis but not autophagy. These changes were associated with a loss of ovarian vessel density and are consistent with an accelerated ovarian aging phenotype. Whether these changes are mediated specifically by a reduction in the local antioxidant environment is unclear, although our data suggest the possibility that ovarian melatonin may play a part in early life nutritional undernutrition and impaired offspring folliculogenesis.

Perinatal winter conditions affect later reproductive performance in Romanian women: intra and intergenerational effects

OBJECTIVES

To compare epidemiological studies on Austrian and New Zealand women that report below average reproductive performance after birth in summer, with a similar study in Romanian women.

METHODS

We examined the association between birth month and offspring count analyzing census data from Romania obtained from IPUMS International (Population and Housing Census of Romania, year 2002), totaling 411,270 women aged older than 45 years. We investigated whether socio-economic status affected this association, and whether intergenerational effects exist for mother's birth month in relation to their daughter's offspring number.

RESULTS

The time series of mean offspring count per birth month has a highly significant period of 12 months. Contrary to our expectations, average offspring count is highest in women born in June and lowest in those born in December, with a strong coincidence between negative peak values of residuals of mean offspring count per birth month and corresponding monthly means of ambient temperature in Romania. The association between winter birth and lower offspring number is significant in poorly educated women only. For mothers born in winter there is also an association with a lower daughters' offspring count.

CONCLUSIONS

Conflicting results exist between Romania and Austria/New Zealand, and may be most easily explained by women's different exposure to winter conditions in these countries.

The impact of maternal birth month on reproductive performance: controlling for socio-demographic confounders

Based on a 1900 census sample of 34,166 post-reproductive females (> or =45 years), the birth month effect was put to the test, for both lifetime fertility as well as child survival, controlling for maternal birth cohort (1826-1835, 1836-1845, 1846-1855), Duncan's SEI, urbanity, nativity, literacy and marital duration. Testing for potential cohort effects did not indicate a temporal trend in fertility by maternal birth month (seasonal Mann-Kendall test, p=0.578), while a minute increase in offspring survival was detected (p<0.001, Sen's estimator of slope=0.02, 95% CI=0.02 to 0.03). Further analyses of the maternal birth month effect on child survival were therefore seized. For lifetime fertility, ANOVA results indicated that maternal birth month was a major predictor for total offspring count (F11, 33606=1809.0, p<0.001), accounting for 37.2% of the total variability. In addition to main effects, a statistically significant interaction effect was observed (F538, 33606=2.2, p<0.001), with a corresponding effect size of eta2=0.40. Planned contrasts revealed that birth-month-specific differences in fertility achieved statistical significance (F11, 31798=1712.9, p<0.001), while post-hoc multiple comparisons for literacy and nativity displayed an inverse relationship with fertility, which meets demographic expectations. Controlling for all factors of interest, models of cohort-specific offspring counts (independent ANOVAs for 1826-1835: F157, 3467=26.3, p<0.001; 1836-1845: F182, 10299=75.5, p<0.001; 1846-1855: F199, 19859=137.9, p<0.001) indicated that women born in the first half of the year (particularly, January, February, April and May) achieved above-average parity, while those born in the latter half (namely, July, October, November and December) displayed markedly lower fertility averages. These monthly disparities are in line with previous observations and appear to be linked to seasonal optimal ripening of the oocyte or seasonal preovulatory over-ripeness ovopathy (Jongbloet, 1992).

Strong association between birth month and reproductive performance of Vietnamese women

Epidemiological studies on premodern and modern Western societies indicate that birth season may influence female reproduction. Nothing is known, however, about this effect in developing economies. Many of the latter are characterised by tropical climates with a rainy season associated with lower food availability and a greater prevalence of infectious diseases. We therefore predict that an association between birth month and reproductive output, if it exists, should be related to the rainy season. To test this prediction, we analysed census data of Vietnam obtained from IPUMS-International (Vietnam 1999 Population and Housing Census). Based on 493,853 women born between 1950 and 1977 and thus aged 22 to 49 years, we found that the time series of mean offspring count per month of birth has a highly significant period of 12 months (power = 46.871, P < 0.00001). Our results further indicate that the 12-month periodic signal has a maximum in July and a minimum in January. Accordingly, the peak corresponds to birth during the rainy season, the low if the third pregnancy month concurs with the rainy season. The month of birth is therefore clearly associated with the later reproductive performance of Vietnamese women, strongly supporting the assumption that environmental and maternal conditions during early development exert long-term effects on reproductive functioning. Provided the rainy season adversely affects developmental processes due to inadequate food and/or high infection risk, the association reported here points to a critical period of reproductive development during early pregnancy.