Table 1.

Characteristics of the studies included.

Author et al.	Study Design	Patients (n)	Age Range	Groups	Assessed Interleukin Polymorphisms	Outcome
Borilova Linhartova et al. [14]	CS/CC	1106 patients	30–77 years	Gp-1: Patients with periodontitis Gp-2: Patients with type-1 DM Gp-3: Patients with periodontitis and type-1 DM Gp-4: Patients with type-2 DM Gp-5: Patients with periodontitis and type-2 DM	IL-1 gene	IL-1B polymorphism is associated with periodontitis. IL-1RN variant is associated with T1DM
López et al. [15]	CS/CC	544 patients	42–68 years	Gp-1: Patients with periodontitis Gp-2: Patients with type-2 DM Gp-3: Patients without type-2 DM and periodontitis	IL-1 gene	IL-1A/1B genotype is not associated with type-2 DM. IL-1 genotype is a risk allele for the development of periodontitis.
Kavitha et al. [16]	CC	120 patients	NR	Gp-1: Patients with periodontitis Gp-2: Patients with type-2 DM Gp-3: Patients with periodontitis and type-2 DM Gp-4: Patients without type-2 DM and periodontitis	IL-6 gene	IL-6 genotype is a risk allele for the development of periodontitis. IL-1 genotype is not associated with type-2 DM.
Deppe et al. [17]	CC	104 patients	48–72 years	Gp-1: Patients with type-2 DM Gp-2: Patients without type-2 DM	IL-1 gene	IL genotypes do not play a role in the progression of periodontitis Poor oral hygiene is a more reliable predictor of periodontitis in patients with and without type-2 DM
Cirelli et al. [18]	CS/CC	894 patients		Gp-1: Patients with periodontitis Gp-2: Patients with periodontitis Gp-3: Patients with type-2 DM	IL-1A, IL-1B, IL-4, IL-6 and IL-10	IL-1B genotype is less likely associated with periodontitis and type-2 DM. IL-4 and IL-6 genotypes are more likely associated with periodontitis and type-2 DM.
Petrovic et al. [19]	CC			Gp-1: Patients with periodontitis Gp-2: Patients with periodontitis and type-2 DM Gp-3: Patients without type-2 DM and periodontitis		IL genes did not show cross-susceptibility with periodontitis and type-2 DM
Xiao et al. [20]	CS/CC	492 patients	40–87 years	Gp-1: Patients with periodontitis Gp-2: Patients with type-2 DM Gp-3: Patients with periodontitis and type-2 DM Gp-4: Patients without type-2 DM and periodontitis	IL-6 gene	Patients in Gp-3 showed the lowest IL-6 genotype and C allele frequencies compared with other groups. The IL-6-572 C allele is a protective factor of diseases progression.
Struch et al. [22]	CS/CC	1515 patients	40–60 years	Gp-1: Patients with type-2 DM Gp-2: Patients without type-2 DM	IL-1A/1B haplotype	IL-1A/1B genotype aggravates periodontitis in patients with type-2 DM.

CS: cross-sectional; CC: case-control; NR: not reported; DM: diabetes mellitus; IL: interleukin.