Summer Birth Research Articles

An epidemiological study of season of birth, mental health, and neuroimaging in the UK Biobank.

Environmental exposures during the perinatal period are known to have a long-term effect on adult physical and mental health. One such influential environmental exposure is the time of year of birth which affects the amount of daylight, nutrients, and viral load that an individual is exposed to within this key developmental period. Here, we investigate associations between season of birth (seasonality), four mental health traits (n = 137,588) and multi-modal neuroimaging measures (n = 33,212) within the UK Biobank. Summer births were associated with probable recurrent Major Depressive Disorder (β = 0.026, pcorr = 0.028) and greater mean cortical thickness in temporal and occipital lobes (β = 0.013 to 0.014, pcorr<0.05). Winter births were associated with greater white matter integrity globally, in the association fibers, thalamic radiations, and six individual tracts (β = -0.013 to -0.022, pcorr<0.05). Results of sensitivity analyses adjusting for birth weight were similar, with an additional association between winter birth and white matter microstructure in the forceps minor and between summer births, greater cingulate thickness and amygdala volume. Further analyses revealed associations between probable depressive phenotypes and a range of neuroimaging measures but a paucity of interactions with seasonality. Our results suggest that seasonality of birth may affect later-life brain structure and play a role in lifetime recurrent Major Depressive Disorder. Due to the small effect sizes observed, and the lack of associations with other mental health traits, further research is required to validate birth season effects in the context of different latitudes, and by co-examining genetic and epigenetic measures to reveal informative biological pathways.

Perinatal factors and early neonatal outcomes of abnormal birthweight infants in Hangzhou, China, 2015–2021: a retrospective cohort study

BackgroundThis study aimed to investigate the perinatal factors and early neonatal outcomes of abnormal birth weight (ABW) in Hangzhou, China from 2015 to 2021.MethodsA retrospective cohort study was designed to...

Mating in the cold. Prolonged sperm storage provides opportunities for forced copulation by male bats during winter.

In a wide range of heterothermic mammals, hibernation interrupts the reproductive cycle by forcing reproductive delays. In hibernating bats with delayed fertilization, an opportunity for sperm competition is enhanced by extending a time-window between copulations and fertilization. In order to achieve greater fertilization success, males are expected to show adaptations for sperm competition by increasing their opportunities for mating over an extended period. We aimed to clarify the physiological and behavioral characteristics of male bats experiencing increased risks of sperm competition. We investigated the characteristics of the reproductive cycle of the little horseshoe bat (Rhinolophus cornutus), and examined whether males retain reproductive physiology related to sexual behavior, and attempt to copulate with females even during the hibernation period. Field observations and histological examinations of the reproductive cycle confirmed that females, having mated in the autumn, store spermatozoa in the uterus during hibernation and give birth in the early summer to just one offspring per year, thus males face a low certainty of successful fertilization. Although their testes regressed rapidly and their testosterone levels were lower during winter than in autumn, males stored motile spermatozoa in their cauda epididymides from autumn throughout the winter. During hibernation, we found that males occasionally aroused from torpor and attempted to mate forcibly with torpid females. Forced copulations appear to increase a male's chances of obtaining a mate while avoiding pre-copulatory female choice. Epididymal sperm storage could be advantageous for males in allowing them to extend their potential mating period even though their testes have regressed. We also found that some hibernating nulliparous females were ready for fertilization in spring after hibernation, whereas few parous females appeared in the same roost. In contrast to males, forced copulations would be maladaptive for females because they cannot opt for higher-quality males while in torpor. Females that have experienced sexual coercion when young may subsequently avoid hibernacula where adult males are present.

Perinatal and early life factors and asthma control among preschoolers: a population-based retrospective cohort study

BackgroundPreventing poor childhood asthma control is crucial for short-term and long-term respiratory health. This study evaluated associations between perinatal and early-life factors and early childhood asthma control.MethodsThis retrospective study used...

Which month to give a birth? The analysis on birth seasonality of China

A series of medical and biological studies have identified a strong link between the season during which a child is born and early childhood development and adult health. While providing an explanation for the seasonal determinants of birth remains one of the key challenges for demographers, understanding seasonal birth peaks and troughs can inform both public health planning and efforts to prevent childhood diseases. The seasonality of births varies across and within countries. Nonetheless, there has been scant research into the seasonality of births in China. This study takes an in depth look at the seasonal fluctuations in China’s births since 1960 and investigates the effects on seasonality of several key factors such as parity, residence (urban or rural area), and changes to fertility policies. Traditionally, winter has been the peak season of births in China, while spring and summer have been lean seasons, a pattern which is quite different than patterns in Europe and the United States. After 1990, the sweeping implementation of one-child policy and the wider use of modern contraceptives among Chinese women prompted a fundamental shift in the seasonality of births, with the deviation of births from month to month gradually diminishing over time. People's self-control may serve as a key determinant accounting for such seasonal changes. First births exhibit pronounced and steady seasonality, while second and subsequent births follow a vague seasonal pattern, suggesting that later births are more likely affected by self-choice and self-intervention. The analysis also reveals that the monthly distribution pattern of second births experienced a dramatic change following the roll-out of the selective-two-child policy and the Universal Two-child Policy in 2014 and 2016, changes that reflects the adjustments people made to achieve their fertility plans under the new policy.

Effect of birth season on allergic rhinitis and cedar pollinosis considering allergen and vitamin D exposure: The Japan Environment and Children's study (JECS)

BackgroundThe relationship between the season of birth, allergen sensitization, and allergic rhinitis have been inconsistent, and there are no studies that simultaneously consider vitamin D and allergen exposure. This study aimed to determine the associations between the season of birth, house dust mite (HDM) and Japanese cedar pollen (JCP) sensitization, and allergic rhinitis and pollinosis, while taking vitamin D levels and allergen exposure into account. MethodsThis study included 4323 participants in the Sub-Cohort Study of the Japan Environment and Children's Study. A logistic regression model was used to analyze the association between the season of birth and sensitization to JCP or HDM (judged by specific immunoglobulin E) at age 2 and allergic rhinitis or pollinosis at age 3, adjusted for HDM or JCP exposure and vitamin D levels with potential confounders. ResultsParticipants born in spring or summer were more likely to have pollinosis than were those born in winter (adjusted odds ratio [aOR]: 2.08, 95% confidence interval [CI]: 1.13–3.82 for spring; aOR: 1.89, 95% CI: 1.03–3.47 for summer). Participants born in summer were more likely to have HDM sensitization than were those born in winter (Der p 1, aOR: 1.53, 95% CI: 1.10–2.15; Der f 1, aOR: 1.44, 95% CI: 1.03–2.01). Exposure to JCP and HDM were associated with pollinosis and HDM sensitization, respectively. ConclusionsSpring and summer births were associated with the development of pollinosis, and summer birth was associated with HDM sensitization, even when vitamin D and allergen exposure were considered. Further studies on mechanisms other than vitamin D and allergen exposure are required.

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

ObjectiveWinter 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. MethodsWe 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. ResultsForty-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. ConclusionsAnalysis 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.

Relationship between seasons and postpartum depression: A systematic review and meta‐analysis of cohort studies

ObjectiveAs the reproduction season's effect on the mental health status is unknown, this study aims to explore the association between seasons and postpartum depression.MethodsA comprehensive search in databases, including PubMed, Cochrane Library, and EMBASE, was performed to identify studies reporting the relationship between reproduction season and postpartum depression. The latter was assessed using certain methods. Moreover, the study design and duration, sample size, the definition of four seasons, outcome assessment, method, and conclusion were extracted. Two independent authors screened the studies independently, and PRISMA 2020 was used as the reporting standard (PRISMA registration ID is 284524).ResultsA total of five studies including 103,986 participants met our criteria. In the sensitivity analysis, the result of the meta‐analysis shows that women who gave birth in spring, summer, or autumn had a lower risk of postpartum depression compared to those who gave birth in winter (RR: 0.83; 95% confidence interval [CI]: 0.78–0.88).ConclusionWomen who gave birth in the other seasons were less likely to have postpartum depression compared to those who gave birth in winter. This result could help couples make overall decisions and help the puerpera take preventive measures against postpartum depression.

Cord blood 25(OH)D3, cord blood total immunoglobulin E levels, and food allergies in infancy: A birth cohort study in Chongqing, China

BackgroundFood allergy (FA) in infants has become a common disease worldwide. There are many controversies surrounding the relationships among levels of cord blood 25-hydroxy vitamin D3 [25(OH)D3], total immunoglobulin E (IgE), and FA. MethodsIn this study, we recruited pregnant women in the third trimester undergoing obstetric examination in Chongqing City, Western China. Healthy full-term singleton births between May to August 2018 and November 2018 to January 2019 were included in the summer-birth and winter-birth cohorts, respectively. Questionnaires on vitamin D status in pregnancy and family allergies were used to investigate the pregnant women. The levels of <12 ng/mL, 12～20 ng/mL, and >20 ng/mL 25(OH)D3 in cord blood detected by liquid chromatography tandem mass spectrometry were considered deficient, insufficient, and sufficient, respectively. The electrochemiluminescence method was used to detect the total lgE levels in cord blood, classified into low-IgE (<0.35IU/mL) and high-IgE (≥0.35IU/mL) levels, respectively. Within postnatal 6 months, allergic symptoms in infants were investigated using questionnaire during the infants’ monthly physical examinations. Suspected cases of FA underwent a history inquiry, skin prick test, food elimination test, and open-food challenge for diagnosis of FA. Multivariate logistic regression was used to analyze the risk factors of FA in infants. ResultsIn this study, we recruited 741 pairs of pregnant women and infants, including 343 infants in the summer-birth cohort and 398 infants in the winter-birth cohort. The incidence of FA within postnatal 6 months was 6.88%, showing significantly higher incidence of FA in the winter-birth cohorts than in the summer-birth cohorts (10.3% vs. 2.9%, χ2 = 15.682, P = 0.000). Among the 741 infants, 47.1%, 27.5%, and 13.8% of infants had deficient, insufficient, and sufficient 25(OH)D3, respectively, in the cord blood; 81.5% and 18.5% of infants had total low-IgE and total high-IgE levels, respectively, in the cord blood. No significant correlation was found between the 25(OH)D3 and IgE levels (r = −0.038, P = 0.300). Logistic regression analysis showed that winter birth [odds ratio (OR) 95% confidence interval (CI): 4.292 (2.003～8.359)] compared with infants in summer birth group, and sufficient (>20 ng/mL) 25(OH)D3 levels in cord blood [OR (95% CI): 2.355 (1.129～4.911) compared with infants in the deficient group (<12 ng/mL) and 3.782 (1.680～8.514) compared with infants in the insufficient group (12～20 ng/mL)] were independent risk factors for FA in infants within postnatal 6 months. ConclusionsWinter birth and sufficient 25(OH)D3 levels in infant cord blood were independent risk factors for FA in infants. 25(OH)D3 and total IgE levels in cord blood cannot be used as predictors of FA in early infancy.

Assessment of Seasonality and Extremely Preterm Birth in Denmark

Preterm birth, particularly extremely preterm birth, has been associated with substantial morbidity and mortality. Research during SARS-CoV-2-related lockdowns revealed reductions in the more severe subtypes of preterm birth in some countries, suggesting the presence of preventable risk factors, such as infectious diseases or social behavior. Seasonality may provide a similar means of assessing natural changes in the daily life of pregnant individuals that were similar to those experienced during the COVID-19 lockdown period. To evaluate the association between seasonality and extremely preterm birth. This nationwide cohort study included 1 136 143 pregnancies in Denmark with onset between January 1, 1997, and December 31, 2016, in which the fetuses survived 21 completed weeks of gestation. Pregnancies were followed up until preterm birth, fetal death, or 37 completed weeks of gestation. Data were analyzed from September 2020 to September 2021. Season during gestation (primary exposure) and season of pregnancy onset. The main outcome of extremely preterm birth was defined as a live birth occurring between 22 weeks, 0 days' gestation and 27 weeks, 6 days' gestation. Cox regression analyses were used to estimate hazard ratios (HRs) for season during gestation and season of pregnancy onset, with adjustment for socioeconomic and demographic factors. Among 662 338 pregnant individuals, the median age at pregnancy onset was 30.0 years (IQR, 6.0 years). Of 1 136 143 pregnancies, 2009 extremely preterm births (cumulative incidence, 0.18%) were identified during follow-up. Season during gestation was associated with extremely preterm birth, with cumulative incidences of 0.17% (95% CI, 0.16%-0.19%) in spring, 0.18% (95% CI, 0.17%-0.20%) in summer, 0.20% (95% CI, 0.18%-0.21%) in autumn, and 0.16% (95% CI, 0.14%-0.17%) in winter. Compared with winter, the adjusted HRs (AHRs) for the risk of extremely preterm birth were 1.11 (95% CI, 0.97-1.26) for spring, 1.15 (95% CI, 1.02-1.31) for summer, and 1.25 (95% CI, 1.10-1.42) for autumn. The number of extremely preterm births associated with the increased risk in the spring, summer, and autumn was 56.1 (95% CI, 18.2-99.7), representing 2.8% (95% CI, 0.9%-5.0%) of all extremely preterm births in the study. Season of pregnancy onset was not associated with the risk of extremely preterm birth in spring (AHR, 0.98; 95% CI, 0.95-1.01) or summer (AHR, 1.00; 95% CI, 0.96-1.03) compared with winter, but a slight increase in risk was observed in autumn (AHR, 1.05; 95% CI, 1.02-1.09) compared with winter. In this large, national cohort study, seasonality was associated with 2.8% of all extremely preterm births. Season during gestation was associated with the rate of extremely preterm birth, suggesting the presence of potential risk factors associated with season that may be preventable. Further research to identify risk factors for extremely preterm birth associated with seasonality is warranted.

Seasonal Variation and Risk of Febrile Seizures: A Danish Nationwide Cohort Study

Introduction: Onset of febrile seizures varies with calendar season. However, it has not previously been assessed, how season of birth interacts with age and peak risk of febrile seizures, and whether season of birth correlates with the cumulative risk of febrile seizures at 5 years of age (i.e., when children are no longer of risk of febrile seizures). Methods: We identified all singleton children born in Denmark between 1977 and 2011 who were alive at 3 months of age (N = 2,103,232). We used the Danish Civil Registration System to identify age and sex of the children and the Danish National Patient Register to identify children hospitalized with febrile seizures from 3 months to 5 years of age. Follow-up ended on December 31, 2016, when all children had reached 5 years of age. Results: The relative risk of admission with a first febrile seizure varied with calendar month; in February (a winter month in Denmark), the risk was more than doubled (hazard ratio: 2.10 [95% confidence interval [CI]: 2.03–2.18]) compared with August (a summer month in Denmark). The age-specific incidence of a first febrile seizure by birth month identified the highest peak incidence of a first febrile seizure among children born in November (reaching a peak incidence of 350 first admissions with a febrile seizure per 100,000 person months at age 16 months) as compared to children born in July (reaching a peak incidence of 200 first admissions with a febrile seizure per 100,000 person months at age 16 months). However, the cumulative incidence of any admission with febrile seizures before 5 years was not correlated with season of birth (3.69% [95% CI: 3.64–3.74%] for winter births, 3.57% [95% CI: 3.52–3.62%] for spring births, 3.55% [95% CI: 3.50–3.59%] for summer births, and 3.64% [95% CI: 3.59–3.69%] for fall births). Discussion/Conclusion: The study found a significant seasonal variation in onset of the first febrile seizure and in the age-specific peak incidence of febrile seizures. However, there was no correlation between season of birth and cumulative incidence of febrile seizures at 5 years of age suggesting that children who are predisposed to febrile seizures will eventually go on to experience a febrile seizure regardless of season of birth.

Early versus late risk factors for deficit and nondeficit schizophrenia

AimWe examined whether timing of known risk factors for schizophrenia may influence the development of schizophrenia with primary negative symptoms. MethodThis cross-sectional single-centre study in England used a clinical cohort of 167 clozapine-treated schizophrenia patients. Deficit and nondeficit schizophrenia models were used as clinical proxies of patients with and without primary negative symptoms respectively. Patients were assessed using the Schedule for the Deficit Syndrome. We examined previously replicated risk factors (family history of psychosis, advanced paternal age, male gender, birth weight <3000g, summer birth, cannabis use, exposure to physical or sexual abuse and/or bullying) as well as other traumatic events for deficit and nondeficit schizophrenia. ResultsWe found a distinct risk factor pattern for the two groups. Compared to the nondeficit group, patients with deficit schizophrenia reported a significantly lower prevalence of cannabis use (p=0.005) at the time of first-episode psychosis (FEP), physical or sexual abuse (p=0.033) prior to FEP, less exposure to crime-related traumatic events (p=0.012) and significantly associated with summer birth (p=0.017). The groups did not differ in terms of family history of psychosis, advanced paternal age, male gender, or low birth weight. To account for multiple comparisons, a confirmatory analysis was performed using logistic regression which yielded similar results except that summer birth no longer reached statistical significance. ConclusionOur results suggest the timing of the insult may influence the symptom presentation, with insults later in life (cannabis or traumatic events) being associated with psychotic presentation and less with primary negative symptoms.

Impact of birth season on second-to-fourth digit ratio, prostate volume, and prostate cancer.

PurposeThe second-to-fourth digit ratio (digit ratio), which is determined in utero, is associated with exposure to visible sunlight during early pregnancy and the season of birth. The digit ratio is also associated with benign prostatic hyperplasia (BPH) and prostate cancer. This suggests that BPH and prostate cancer may be related to the birth season. Therefore, this study aimed to determine whether prostate volume and prostate cancer were related to the birth season.Materials and MethodsA total of 858 male patients with lower urinary tract symptoms were enrolled. The right digit ratio was measured, and the month of birth was surveyed. Serum prostate-specific antigen (PSA) levels were measured, and prostate volumes were measured by transrectal ultrasonography. Patients with suspected prostate cancer underwent prostate biopsy.ResultsThe mean age, digit ratio, prostate volume, and serum PSA level of 858 patients were 61.6 years, 0.947, 36.2 mL, and 4.24 ng/mL, respectively. Age, serum PSA levels, prostate biopsy rates, and cancer detection rates did not differ significantly according to the birth season. However, compared with the summer birth group, the winter birth group had lower digit ratios (0.951±0.040 vs. 0.941±0.040; p=0.014), larger prostate volumes (33.4±14.9 mL vs. 38.2±20.7 mL; p=0.008), and more prostate cancer (5.3% vs. 11.3%; p=0.031). Multivariate analysis showed that birth season independently predicted prostate cancer.ConclusionsThe relationships of birth season with prostate volume and prostate cancer may be due to differences in the amount of light exposure during early pregnancy.

Season of Birth and Cardiovascular Mortality in Atrial Fibrillation: A Population-Based Cohort Study.

Background: The fetal origins hypothesis have associated early life exposures with the development of adverse health outcomes in adulthood. Season of birth has been shown to be associated with overall and cardiovascular mortality. Methods: We performed a retrospective database study to explore the association between season of birth and mortality in patients with atrial fibrillation. Results: A total of 8962 patients with AF were identified in the database with 1253 deaths recorded. AF patients born in spring and summer had a higher mortality rate when compared to those born in autumn and winter (hazard ratio (HR) 1.13, 95% confidence interval (CI) 1.01–1.26, p = 0.03). This effect was consistent in the male subgroup (HR 1.25, 95% CI 1.03–1.51, p = 0.02 for males born in spring; HR 1.24, 95% CI 1.03–1.51, p = 0.03 for males born in summer when compared to winter as the reference) but not in females (HR 1.02, 95% CI 0.79–1.31, p = 0.88 for females born in spring; HR 1.11, 95% CI 0.87–1.42, p = 0.39 for females born in summer when compared to winter as the reference). Results persisted after adjustment for baseline characteristics and clinical risk profile. A similar pattern was observed with cardiovascular mortality. Conclusion: Birth in spring or summer is associated with a higher risk of cardiovascular mortality in male AF patients, but not in females. This could be related to the underlying differences in rates of major adverse clinical events between genders. Further studies should aim at clarifying the mechanisms behind this association, which may help us understand the higher level of risk in female patients with AF.

Season of birth and cardiovascular mortality in atrial fibrillation: a population-based cohort study

Abstract Funding Acknowledgements Type of funding sources: None. Background. Month and season of birth may be indicators for a variety of prenatal and early postnatal exposures and they have been associated with life expectancy in adulthood. It is suggested that people born in the autumn on the northern hemisphere live longer than those born during the spring or summer, who may have an increase in cardiovascular disease specific mortality. Only few studies have followed populations longitudinally and no study has investigated the relation between season of birth and mortality in patients with established cardiac conditions. Methods. All patients with atrial fibrillation (AF) seen in an academic institution were identified in a database. We examined the clinical course of 8962 consecutive patients with AF seen over a 10-year period. The adverse outcomes were investigated during follow-up and we identified the causes of death. The relation between season of birth (autumn, winter, spring and summer) and mortality risk was assessed using Cox proportional hazard regression models using autumn as the reference. Analyses were also made separately for men and women. Results. In these 8962 patients (age 70 ± 10 years, CHA2DS2VASc score 3.1 ± 1.7), 1253 deaths were recorded during a follow-up of 2.5 ± 3.0 years (median 1.2, interquartile 4.3 years, yearly rate of death 5.5%) and 97% of causes of death were identified. Cardiovascular deaths accounted for 54% and 43% for non-cardiovascular. The three main causes of death were heart failure (29%), infection (18%) and cancer (12%). Season of birth was a significant predictor of cardiovascular mortality (overall p = 0.0006). The lowest mortality was seen for people born in autumn or winter and the highest mortality in those born in spring and summer. This was mainly related to a higher cardiovascular mortality in males (hazard ratio [HR] 1.46, 95%CI 1.10-1.93, p = 0.009 for males born in spring and HR 1.44, 95%CI 1.08-1.91, p = 0.01 for those born in summer when compared to males born in autumn as the reference) while this effect was not seen in women. In a model adjusted for age, CHA2DS2VASc score, HASBLED score, cardiovascular risk factors, other comorbidities, AF pattern, antithrombotic use and other cardiovascular drugs use, a higher cardiovascular mortality was still seen in males born in spring (adjusted HR 1.43, 95%CI 1.05-1.96, p = 0.03) or in summer (adjusted HR 1.46, 95%CI 1.07-1.99, p = 0.02) when compared to those born in autumn while this was not seen in women. Conclusion. Birth in spring or summer is associated with a higher risk of cardiovascular mortality in male AF patients. Further studies should aim at clarifying the mechanisms behind this association, which would support the so-called fetal origins hypothesis.

Early versus late risk factors for deficit and nondeficit schizophrenia.

We examined whether timing of known risk factors for schizophrenia may influence the development of schizophrenia with primary negative symptoms. This cross-sectional single-centre study in England used a clinical cohort of 167 clozapine-treated schizophrenia patients. Deficit and nondeficit schizophrenia models were used as clinical proxies of patients with and without primary negative symptoms respectively. Patients were assessed using the Schedule for the Deficit Syndrome. We examined previously replicated risk factors (family history of psychosis, advanced paternal age, male gender, birth weight <3000g, summer birth, cannabis use, exposure to physical or sexual abuse and/or bullying) as well as other traumatic events for deficit and nondeficit schizophrenia. We found a distinct risk factor pattern for the two groups. Compared to the nondeficit group, patients with deficit schizophrenia reported a significantly lower prevalence of cannabis use (p=0.005) at the time of first-episode psychosis (FEP), physical or sexual abuse (p=0.033) prior to FEP, less exposure to crime-related traumatic events (p=0.012) and significantly associated with summer birth (p=0.017). The groups did not differ in terms of family history of psychosis, advanced paternal age, male gender, or low birth weight. To account for multiple comparisons, a confirmatory analysis was performed using logistic regression which yielded similar results except that summer birth no longer reached statistical significance. Our results suggest the timing of the insult may influence the symptom presentation, with insults later in life (cannabis or traumatic events) being associated with psychotic presentation and less with primary negative symptoms.

Grow or go? Energetic constraints on shark pup dispersal from pupping areas.

Many sharks and other marine taxa use natal areas to maximize survival of young, meaning such areas are often attributed conservation value. The use of natal areas is often linked to predator avoidance or food resources. However, energetic constraints that may influence dispersal of young and their use of natal areas are poorly understood. We combined swim-tunnel respirometry, calorimetry, lipid class analysis and a bioenergetics model to investigate how energy demands influence dispersal of young in a globally distributed shark. The school shark (a.k.a. soupfin, tope), Galeorhinus galeus, is Critically Endangered due to overfishing and is one of many sharks that use protected natal areas in Australia. Energy storage in neonate pups was limited by small livers, low overall lipid content and low levels of energy storage lipids (e.g. triacylglycerols) relative to adults, with energy stores sufficient to sustain routine demands for 1.3–4 days (mean ± SD: 2.4 ± 0.8 days). High levels of growth-associated structural lipids (e.g. phospholipids) and high energetic cost of growth suggested large investment in growth during residency in natal areas. Rapid growth (~40% in length) between birth in summer and dispersal in late autumn–winter likely increased survival by reducing predation and improving foraging ability. Delaying dispersal may allow prioritization of growth and may also provide energy savings through improved swimming efficiency and cooler ambient temperatures (daily ration was predicted to fall by around a third in winter). Neonate school sharks are therefore ill-equipped for large-scale dispersal and neonates recorded in the northwest of their Australian distribution are likely born locally, not at known south-eastern pupping areas. This suggests the existence of previously unrecorded school shark pupping areas. Integrated bioenergetic approaches as applied here may help to understand dispersal from natal areas in other taxa, such as teleost fishes, elasmobranchs and invertebrates.

Seasonal Gene Expression in Human Placenta

Background: Seasonal exposures influence human health and development. The placenta, as a mediator of the maternal and fetal systems and a regulator of development, is an ideal tissue to understand the biological pathways underlying relationships between season of birth and later life health outcomes. Rhythmic seasonal gene expression in the placenta could provide a molecular explanation for the associations between season of birth and later life disease.Methods: We investigated whether transcriptome-wide placental gene expression had seasonal or monthly patterns in the Rhode Island Child Health Study (RICHS). We performed a differential expression analysis of season of birth, defined by the solstice and equinox dates to bin by photoperiod. Additionally, we evaluated whether placental gene expression displayed rhythmicity by conducting a cosinor analysis of birth month. Results were adjusted for multiple comparisons using the Benjamini and Hochberg or Bonferroni methods.Results: Of the analyzed transcripts, 583 displayed differential expression between summer and winter births (FDR q&lt;0.05); among these, BHLHE40, MIR210HG, and HILPDA had increased expression among winter births (Bon p&lt;0.05). Enrichment analyses indicated over-representation of transcription factors HIF1A, VDR, and CLOCK, among others, and of GO term pathways related to ribosomal activity and infection between summer and winter births. Additionally, the cosinor analysis found rhythmic expression for approximately 11.9% of all 17,664 analyzed placental transcripts.Conclusion: These results suggest that the placenta responds to seasonal cues and acts as a peripheral clock; results also suggest seasonal changes in placental inflammation and hypoxia, which may provide a molecular explanation for the extensive associations between season of birth and health outcomes. Further study of seasonal and circadian effects on the placenta could shed light on the pathways that influence the associations between season of birth and human health, as well as possible therapeutic targets.

The Reproductive Ecology of the Bank Vole Myodes (Clethrionomys) glareolus Schreb. in North Periphery of Its Areal: I. Sex Cycles, Course, Dates, and Intensive Reproduction

A characterization of long-term station and field studies (1958–2017) on the tiaga in northwestern Russia is given for the population-ecology features of reproduction of the bank vole, including those associated with its habitat at the northern borders of its distribution: reproductive cycles and the timing, course, and intensity of reproduction. According to the dates, including from the results of histological examination of the gonads, under the conditions of the northern periphery of its range, the bank vole has a long breeding period from April to September with the very intensive participation of young fertile voles, especially early spring–summer births. The male reproductive cycle has a stage of passive spermatogenesis with a rapid increase in the epithelium and the appearance of spermatocytes of both orders. From April, active spermatogenesis occurs, during which the epithelium of germinal becomes layered and mature spermatozoa appear in the tubules and appendages of the testis. Ovulation in females, apparently, is spontaneous, as is evidenced by cases of the presence of a false corpus luteum in adult (overwintered) females, as well as in newcomers, the reproduction of which is interrupted by seasonal depression. The average duration of the sexual cycle is 5–6 days; the maximum is about two weeks. In this article a function of population autoregulation, which depends on the initial population density of the adaptive shift involved in the reproduction of age-related generations of animals, is revealed.

Seasonally variant gene expression in full-term human placenta.

Seasonal exposures influence human health and development. The placenta, as a mediator of the maternal and fetal systems and a regulator of development, is an ideal tissue to understand the biological pathways underlying relationships between season of birth and later life health outcomes. Here, we conducted a differential expression (DE) analysis of season of birth in full-term human placental tissue to evaluate whether the placenta may be influenced by seasonal cues. Of the analyzed transcripts, 583 displayed DE between summer and winter births (False Discovery Rate [FDR] q<.05); among these, BHLHE40, MIR210HG, and HILPDA had increased expression among winter births (Bonferroni P<.05). Enrichment analyses of the seasonally variant genes between summer and winter births indicated overrepresentation of transcription factors HIF1A, VDR, and CLOCK, among others, and of GO term pathways related to ribosomal activity and infection. Additionally, a cosinor analysis found rhythmic expression for approximately 11.9% of all 17664 analyzed placental transcripts. These results suggest that the placenta responds to seasonal cues and add to the growing body of evidence that the placenta acts as a peripheral clock, which may provide a molecular explanation for the extensive associations between season of birth and health outcomes.