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Preemies & Diabetes: a Study of How They are Connected 

May 19, 2020
Editor: David L. Joffe, BSPharm, CDE, FACA

Author: Deonna Andrews, PharmD Candidate 2020 of Florida Agricultural & Mechanical University College of Pharmacy and Pharmaceutical Sciences 

With the steady incline of diabetes rates, premature birth is being investigated as a possible culprit for the chronic disease. In what way are preemies and diabetes linked?

Diabetes affects nearly 1 in 10 adults in the United States and worldwide. Family history and unhealthy lifestyle decisions are known risk factors that lead to either type 1 or type 2 diabetes. Additionally, early life exposures have been identified as an additional potential risk factor for the development of diabetes later in life.  


Previous studies that researched preterm births and diabetes had a primary focus on childhood <15 years of age and found that there was an increased risk of type 1 diabetes in persons born prematurely. Type 2 diabetes was also studied in a few other trials and was found in persons mid-adulthood. However, these studies did not shed light on whether the risk of diabetes was associated with shared familial (genetic or environmental) factors that predispose to both preterm birth and diabetes, as opposed to just direct effects of preterm birth. Also, no research examines both type 1 & 2 diabetes and potential sex-specific differences from childhood to adulthood in a large cohort.  

To bridge this knowledge gap, researchers conducted a national cohort study of over 4 million people in Sweden. Researchers of this large cohort study examined the associations between gestational age at birth and risk of type 1 or type 2 diabetes, up to 43 years of age. From there, they assessed the difference of these associations to include: sex, fetal growth, and potential confounding by shared familial factors using co-sibling analyses.  

This national cohort study used the Swedish Birth Registry to identify all 4,193,069 singleton live births in Sweden from 1973–2014 for the inclusion of this study. This study only used de-identified registry-based secondary data, so participant consent was not required.  

Gestational age at birth was initially collected as the report of the last menstrual period in the 1970s and then progressed to ultrasonography estimation in 1980. This was analyzed as a continuous, categorical variable with six groups: extremely preterm (22–28 weeks), very preterm (29–33 weeks), late preterm (34–36 weeks), the earlyterm (37–38 weeks), full-term (39–41 weeks, used as the reference group), and post-term (≥42 weeks). Since earlyterm births were previously studied as being an increased risk of diabetes-related mortality relative to laterterm birth, it was examined as a separate category.  

The earliest diagnosis of type 1 & 2 diabetes was followed up from birth until the end of following in 2015, with the maximum age being 43 years. Different defining criteria established type 1 and type 2 diabetes. Type 1 diabetes was defined as any ICD code specific for type 1 diabetes, including ICD 9 and 10, and any other ICD code for diabetes combined with an insulin prescription before the age of 30 years. Type 2 diabetes was defined as not meeting the criteria for type 1 diabetes and ICD codes for diabetes.  

The Cox proportional hazards regression model determined hazard ratios and 95% confidence intervals. This allowed researchers to examine the connection between gestational age at birth and incident type 1 or 2 diabetes. Since there was potential for confounding effect, a co-sibling analysis was performed to assess the unmeasured shared familial factors among individuals with at least one full sibling. Doing this provides transparency between the direct effects of preterm birth as opposed to shared genetic or environmental factors that predispose to both preterm birth and diabetes. 

In reviewing the results of the associations between gestational age at birth and diabetes, 27,512 (0.7%) individuals were identified with type 1 diabetes, and 5525 (0.1%) individuals were identified with type 2 diabetes. In the overall cohort, the type 1 diabetes incidence rate was 29.80, with 36.78 being born preterm and 28.80 being born full-term. In type 2 diabetes, the overall incidence rate was 5.98, with 8.48 being born preterm and 5.56 being born full-term.  

The results of this study confirm the speculations that preterm birth is associated with increased risks of type 1 and type 2 diabetes from childhood into early to mid-adulthood. Contrarily, researchers found that the children born extremely preterm had a lower risk of developing type 1 diabetes and higher risk of developing type 2 diabetes. 

Practice Pearls: 

  • In this study preterm birth was associated with the development of diabetes, either type 1 or 2, later in life. 
  • Women are affected more than men, and type 1 diabetes was more prevalent than type 2 diabetes.  
  • Clinicians should take into consideration this population of people, the possible long-term risks, and assess opportunities for prevention. 

Reference for “Preemies & Diabetes: a Study of How They are Connected”:
Crump, Casey et al. “Preterm birth and risk of type 1 and type 2 diabetes: a national cohort study.”
Diabetologia vol. 63,3 (2020): 508-518. doi:10.1007/s00125-019-05044-z 


Deonna Andrews, PharmD Candidate 2020 of Florida Agricultural & Mechanical University College of Pharmacy and Pharmaceutical Sciences  



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