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Environmental Factors of Type 1 Diabetes Development: Diabetes & Our Environments: Part I

What does type 1 diabetes, happening inside our bodies, have to do with the environment around us? The intersections might not seem immediately obvious, but health is inextricably linked with our surroundings. From the air we breathe to the water we drink and the food we eat, our health is in constant interplay with the places in which we work, live, play, and learn. Diabetes is certainly involved in these interactions, and even more so while our climate is rapidly changing. In this blog series, we will explore the complex relationships between our environments and type 1 diabetes.

First, we’ll go back to where every diabetes story starts–diagnosis! After all these years of diabetes research, we still aren’t really sure what causes type 1 diabetes because it’s so complicated. The likelihood that a person’s immune system attacks their beta cells is thought to be influenced by a combination of genetic and environmental factors.

There are many lines of evidence that point to type 1 diabetes having an environmental component. For example, a relatively small percentage of people with known genetic risk factors for type 1 diabetes actually go on to develop it. Studies of identical twins have shown that if one twin has type 1 diabetes, there is less than a 40% chance that both will have it. And contrary to popular belief, most people diagnosed with T1D have no family history of it! (7). The incidence of type 1 diabetes has also been significantly increasing recently, and incidence varies by geographic region (1).

So what kinds of environmental factors are we talking about here? There are a lot of hypothesized links between our environments and the onset of type 1 diabetes, but keep in mind that it’s challenging to draw definitive conclusions. Remember: association does not equal causation! Meaning, even if a particular environmental factor is strongly associated with type 1 diabetes, the factor itself did not necessarily cause type 1 diabetes. It is also important to note that these environmental factors do not work alone, but rather in relation to one another and other biological and social conditions.

  • Seasonality and viruses: The onset of type 1 diabetes has been observed to occur more frequently during the cold months of the year (1, 2). It is thought that this may be due to viruses being more rampant in cold, dry conditions. Many reports cite viral infections, particularly from enteroviruses, as a potential cause of type 1 diabetes (3). There is also emerging evidence that COVID-19 infection can increase the risk of developing type 1 diabetes (4, 5). COVID-19 is a zoonotic virus, meaning it originated in animals. Spillover events where animal viruses become able to infect humans are projected to become more common with climate change and environmental degradation.
  • The microbiome: It has been hypothesized that intestinal microbiota, or the collection of microorganisms living in the gut, can contribute to the development of T1D (3). Many things in our environment affect the composition of our intestinal microbiota, especially during early childhood. For example, birth delivery route, early childhood diet, and exposure to antibiotics have all been shown to affect what kind of microbes take up residence in the gut.
  • Nutrition: Many aspects of early childhood diet and maternal diet have been explored as potential factors in type 1 diabetes development (e.g. cow’s milk, cereals, omega-3 fatty acids, vitamin D) (3). However, much of the evidence in this area remains unclear and requires more research.
  • Stress: Other environmental promoters of type 1 diabetes progression seem to cause increased insulin demand and beta cell stress (3). Some circumstances that may lead to this increased beta cell stress include periods of rapid growth, puberty, and even serious life events and traumas.
  • Toxicity: It has been proposed that various toxicants and environmental pollutants may be at least partially responsible for the increasing prevalence of type 1 diabetes. For example, a handful of studies have found an association between air pollution and type 1 diabetes (6).

It’s not uncommon for type 1 diabetes diagnoses to seemingly come from out of the blue (“No one in my family had it!”). But considering all of the different factors that influence the development of type 1 diabetes, this may not be so surprising.

Though the development of T1D seems to have an environmental component, no one is responsible for having diabetes. People’s environments are shaped by influences outside of their control. Quality of air, food, and water, healthcare access, and social conditions are determined by systems, not individuals. As we learn more about how environmental factors contribute to type 1 diabetes, structural efforts to support healthy environments for both people living with diabetes and people at risk of developing diabetes are essential.

References

  1. Environmental Triggers and Determinants of Type 1 Diabetes, Mikael Knip, Riitta Veijola, Suvi M. Virtanen, Heikki Hyöty, Outi Vaarala, Hans K. Åkerblom, Diabetes Dec 2005, 54 (suppl 2) S125-S136; DOI: 10.2337/diabetes.54.suppl_2.S125
  2. Moltchanova, E V et al. “Seasonal variation of diagnosis of Type 1 diabetes mellitus in children worldwide.” Diabetic medicine: a journal of the British Diabetic Association vol. 26,7 (2009): 673-8. doi:10.1111/j.1464-5491.2009.02743.x
  3. Rewers, Marian, and Johnny Ludvigsson. “Environmental risk factors for type 1 diabetes.” Lancet (London, England) vol. 387,10035 (2016): 2340-2348. doi:10.1016/S0140-6736(16)30507-4
  4. Qeadan F, Tingey B, Egbert J, Pezzolesi MG, Burge MR, Peterson KA, et al. (2022) The associations between COVID-19 diagnosis, type 1 diabetes, and the risk of diabetic ketoacidosis: A nationwide cohort from the US using the Cerner Real-World Data. PLoS ONE 17(4): e0266809. https://doi.org/10.1371/journal.pone.0266809
  5. CDC, Risk for Newly Diagnosed Diabetes >30 Days after SARS-CoV-2 Infection among Persons Aged <18 Years – United States, March 1, 2020 – June 28, 2021. https://www.cdc.gov/mmwr/volumes/71/wr/mm7102e2.htm
  6. Hathout, Eba H et al. “Air pollution and type 1 diabetes in children.” Pediatric diabetes vol. 7,2 (2006): 81-7. doi:10.1111/j.1399-543X.2006.00150.x
  7. Parkkola, A., Härkönen, T., Ryhänen, S. J., Ilonen, J., Knip, M., & Finnish Pediatric Diabetes Register (2013). Extended family history of type 1 diabetes and phenotype and genotype of newly diagnosed children. Diabetes care, 36(2), 348–354. https://doi.org/10.2337/dc12-0445
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