Open Access

Table I

Risk of bias; N = number of studies considered adequate for the corresponding element.

Study characteristics Studies N Bias risk evaluation Studies N
Year of publication Selection
≤2010 2 Definition of case 14
2011–2015 11 Selection of case 14
≥2016 1 Definition of controls 14
    Selection of controls 14
Study design   Comparability  
Case control 14 As a function of age *  
    <18 years old 1
    25–40 years old 3
Type of periodontitis   Over 40 years old 10
Chronic periodontitis 12    
Unspecified periodontitis 2 As a function of sex  
    Equality respected 2
Leptin studied   Differences between male and female 11
Salivary 5 Not mentioned 1
Serum 12    
    Size of group  
    <60 6
    >60 8
    As a function of other factors (BMI) 14
    Measurement criteria  
    Measurement description 14
    Measurement validation 14

Only one study provided the average age (Karthikeyan 2007 [18]).

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