Table 1. Summary of mentioned articles about shared genetic background and environmental factors in T1DM and CD.

T1DM, type 1 diabetes mellitus; CD, celiac disease; HR, hazard ratio; OR, odds ratio; HLA, human leukocyte antigen; US, United States; IA, islet autoimmunity

Author	Year	Design	Population	Global Sample	Results	Conclusions
Siddiqui et al. [20]	2021	Cross-sectional	Pediatric samples from the Isra University Hospital, Liaquat University of Medical and Health Sciences Hospital and Asian Institute of Medical Sciences Hospital, Hyderabad, India	175 pediatric individuals with T1DM or CD	In patients with CD, DQ2 was found in 85.7%, DQ8 in 11.4%, and DQ2/DQ8 at the same time in 2.8%.  In the group of concurrent CD and T1DM, DQ2 was found in 31.4%, CD8 in 25%, and DQ2/DQ8 in 34% and just nine of these individuals were experimenting CD	The most frequent haplotypes present in these population were DQ2 and DQ8 coming after and they could be used for a more accurate diagnosis in selected cases
Farina et al. [25]	2019		Children enrolled in a Hospital of Naples, Italy	21 patients with T1DM	DR3-DQA1*05 and DQB1*02 alleles encode for DQ2 molecule and DR4-HLA DQA1*03 and DQB1*03 alleles encode DQ8 molecules	DQ2.5 and DQ8 risk alleles are more frequent than non-associated alleles in T1DM patients
Frederiksen et al. [28]	2013	Longitudinal, observational study	Newborns at St. Joseph’s Hospital in Denver, Colorado	1,835 children at risk for T1DM	Early exposure to any solid food (HR: 1.91. 95%. CI: 1.04-3.51) and late first exposure (HR: 3.02; 95% CI: 1.26-7.24) predict risk of development of T1DM	There is a period of time, between four and six months, to introduce solid foods without increasing the IA risks. The risk of developing IA was reduced when gluten was introduced while breastfeeding
Ivarsson et al. [29]	2002	Prospective study	Swedish children	524 children	The risk to develop CD was reduced if a child is being breastfed when gluten is introduced in its diet (OR: 0.59; 95% CI: 0.42-0.83)	Reduced development of CD in children under two years old who were breastfed while the gluten was introduced and probably also reduced risk of development in the next childhood phase
Norris et al. [30]	2003	Birth cohort study	Newborns at St Joseph's Hospital in Denver, Colorado	1,183 children at increased type 1 DM risk	Children who were exposed to cereal in the first three months of age (HR: 4.32; 95% CI: 2.0-9.35) and the ones who were exposed after six months (HR: 5.36; 95% CI: 2.08-13.8) had an increased risk of IA	The risk of IA increases if exposure to cereals is outside a window of time between four and six months of age
Lönnrot et al. [31]	2017	Prospective international cohort study	Children enrolled in six clinical research centers: three in the US (Colorado, Georgia/Florida, and Washington State) and three in Europe (Finland, Germany, and Sweden)	8,676 children	The risk of IA was associated with the number of respiratory infections given in a nine-month frame of time (p < 0.001).  The hazard of IA increased approximately 5.6% for every one per year rate increase in infections from the respiratory tract	Respiratory infections occurring in young children were associated with the subsequent risk of autoimmunity