Seasonality of month of birth of children (0-14 years old) with type 1 diabetes mellitus in the District of Catania, Sicily

Lack of association between month of birth and risk of developing type 1 diabetes in Brazil: a 40-year analysis

OBJECTIVES

Seasonal environment at birth may influence diabetes incidence in later life. We sought evidence for this effect and analyzed the association between the month of birth and the risk of developing type 1 diabetes mellitus (T1DM).

METHODS

This was a cohort study carried out with 814 patients diagnosed with T1DM in the region of Bauru - São Paulo State, Brazil, receiving medical care in a private Endocrinology clinic or in the public Brazilian National Health Care System, from 1981 to 2021. All live births that occurred in São Paulo State between 1974 and 2020 were classified by month of birth and were considered as the control group.

RESULTS

We found no statistically significant difference (χ2=16.31, critical 19.68) between the month of birth and risk of developing T1DM, when comparing our patients with the background population of the region. There was no association between the month of birth, sex, age at diagnosis, duration of symptoms before diagnosis, self-reported color, and socioeconomic status.

CONCLUSIONS

We found no association between month of birth and the risk of developing T1DM in this highly admixed South American population. Our data suggest that our population heterogeneity and geographic location may be important factors in the development of T1DM. Future prospective studies, evaluating environmental factors that may confer risk or protection to the disease, are warranted.

Seasonality of month of birth in patients with autoimmune endocrine diseases: A systematic review

BACKGROUND

Exposure to seasonal environmental factors during gestation or early in the postnatal period could influence the development of autoimmunity, determining a seasonality in the month of birth (MOB). There are studies evaluating this potential seasonality in patients with type 1 diabetes (T1D), autoimmune thyroid diseases (AITD), and Addison's disease (ADD), but results have been controversial.

METHODS

Systematic review according to PRISMA guidelines, using PubMed, Web of Science and WorldCat databases (2005-2020) of studies that explored the association between the seasonality of the MOB and T1D, AITD and ADD. Information on sex and age, location, methodology and internal quality, seasonal patterns, hypotheses and other factors proposed to explain seasonality were extracted. Differences in season and month of birth were further discussed.

RESULTS

The initial search retrieved 300 articles, and after further screening, 11 articles fulfilled inclusion criteria and were finally selected and reviewed. 73% found a seasonal pattern and 64% showed birth peaks in spring and/or summer. Hashimoto's thyroiditis and women exhibited a higher seasonality. Ultraviolet radiation, Vitamin D levels and viral infections were identified as influencing factors.

CONCLUSIONS

The effect of certain seasonal factors during foetal development, reflected by the seasonal differences in the MOB, could contribute to the development of endocrine autoimmune diseases in predisposed patients. Further research is needed to elucidate the mechanisms underlying the observed seasonality.

Variation in the incidence of type 1 diabetes mellitus in children and adolescents by world region and country income group: A scoping review

INTRODUCTION

Around 18.7 million of the 537 million people with diabetes worldwide live in low-income and middle-income countries (LMIC), where there is also an increase in the number of children, adolescents, and young adults diagnosed with type 1 diabetes (T1D). There are substantial gaps in data in the current understanding of the epidemiological patterns and trends in incidence rates of T1D at the global level.

METHODS

We performed a scoping review of published studies that established the incidence of T1D in children, adolescents, and young adults aged 0-25 years at national and sub-national levels using PubMed, Embase and Global Health. Data was analyzed using R programming.

RESULTS

The scoping review identified 237 studies which included T1D incidence estimates from 92 countries, revealing substantial variability in the annual incidence of T1D by age, geographic region, and country-income classification. Highest rates were reported in the 5-9 and 10-14 year age groups than in the 0-4 and 15-19 year age groups, respectively. In the 0-14 year age group, the highest incidence was reported in Northern Europe (23.96 per 100,000), Australia/New Zealand (22.8 per 100,000), and Northern America (18.02 per 100,000), while the lowest was observed in Melanesia, Western Africa, and South America (all < 1 per 100,000). For the 0-19 year age group, the highest incidence was reported in Northern Europe (39.0 per 100,000), Northern America (20.07 per 100,000), and Northern Africa (10.1 per 100,000), while the lowest was observed in Eastern and Western Africa (< 2 per 100,000). Higher incidence rates were observed in high-income countries compared to LMICs. There was a paucity of published studies focusing on determining the incidence of T1D in LMICs.

CONCLUSION

The review reveals substantial variability in incidence rates of T1D by geographic region, country income group, and age. There is a dearth of information on T1D in LMICs, particularly in sub-Saharan Africa, where incidence remains largely unknown. Investment in population-based registries and longitudinal cohort studies could help improve the current understanding of the epidemiological trends and help inform health policy, resource allocation, and targeted interventions to enhance access to effective, efficient, equitable, and responsive healthcare services.

Month of birth predicted reproductive success and fitness in pre-modern Canadian women

Conditions experienced during early development affect human health and survival in adulthood, but whether such effects have consequences for fitness is not known. One surrogate for early conditions is month of birth, which is known to influence health and survival in many human populations. We show that in nineteenth century Canada, month of birth predicted a woman's fitness measured by the number of grandchildren produced, with the genetic contribution to the following generations by women born in different months differing by over seven grandchildren. This difference was mainly caused by differences in the reproductive rates of both mothers and their offspring, rather than differences in their survival. Women born in the best months of the year had longer reproductive lifespans, larger numbers of live births and raised more offspring to adulthood than those who were born in the worst months. Furthermore, the offspring of those women born in the best months also had greater reproductive rates, suggesting that month of birth also influenced a mother's ability to invest in her offspring. Our results suggest that early conditions may have important consequences for human lifetime reproductive performance within and between generations, and that timing of birth had large effects on fitness in this rural community.

Interplay between heredity and environment in the recent explosion of type 1 childhood diabetes mellitus

The fast increase in the incidence of childhood type 1 diabetes mellitus (T1DM) that cannot be explained by changes in the genetic susceptibility, led us to look for environmental causes. To test the hypothesis that the initiation of the autoimmune process of childhood T1DM in genetically susceptible subjects begins in the perinatal period by a viral infection, we studied the seasonal variations in the month of birth of several cohorts of patients compared to the general population. Population groups with high or low T1DM incidence were analyzed separately by t-test and the Cosinor methods. In areas with populations with a high incidence (Israeli Jews, Sicily, Sardinia, Slovenia, Germany) we found that the children (in Sicily also young adults) who subsequently developed T1DM, have a higher incidence of births in the summer months than in other seasons of the year, a mirror image of the seasonality of the clinical onset of disease. This pattern differed significantly from the seasonality of the total live births in the same populations. In populations with a low T1DM incidence, (China, Japan and Cuba) no seasonality of month of birth was found. Similar findings have been reported, from five counties in the U.K. and the Netherlands. It is hypothesized that mothers who become pregnant during the period of yearly viral epidemics transmit to the fetus, either a virus or antiviral antibodies, which determine whether an autoimmune process against the pancreatic beta is initiated or whether the fetus is protected against that process.

Seasonality of birth in children (0-14 years) with type 1 diabetes mellitus in Slovenia

The aim of this study was to find out whether there is seasonality of month of birth of children with diabetes in Slovenia and if so whether it differs from that of the general population. A cohort of 849 children and adolescents (0-14 years) with type 1 diabetes mellitus born between 1956 and 1998 were included in the study. Monthly and seasonal patterns of birth of the patients with diabetes were compared with the pattern of normal live births (n = 1,345,921) and the pattern of disease onset. Statistical analysis was made using Student's t-test to compare the means between the four seasons of the year, and single cosinor analysis for a period of 12 months. The children and adolescents with diabetes had a statistically significant different seasonality of month of birth compared to that of the general population, and an opposite pattern from the seasonality of month of onset of disease. The observations made are in accordance with observations made recently in other countries and support the hypothesis that a virus infection transmitted by the mother to the fetus during the annual viral epidemic induces the autoimmune process in the pancreatic beta-cells in genetically susceptible individuals who will subsequently develop clinical diabetes during childhood.