“…A higher prevalence of medical comorbidities was observed, in ascending order, in studies by Javali et al (40.21%; n=455) [ 40 ], Mesgarzadeh et al (41.01%; n=968) [ 48 ], Al-Bayaty et al (41.9%; n=571)[ 33 ], Siddiqi et al (47%; n=12 960) [ 49 ], Kaur (48.2%; n=1260) [ 50 ], Saengsirinvin et al (55.45%; n=541) [ 51 ], Umino et al (64.2%; n=1012; elderly only) [ 52 ], Cottone et al (68.5%; n=4365) [ 53 ], and Maryam et al (73.3%; n=1188) [ 36 ], with the highest prevalence reported by Frydrych et al (86%; n=873) [ 37 ]. The differences in prevalence can be attributed to regional (country) population health differences (Saudi Arabia [ 39 , 40 , 42 ], Iran [ 36 , 48 ], India [ 38 , 47 , 50 ], Pakistan [ 41 , 49 ]), as substantiated by studies that determined regional differences in diseases [ 54 ]. The differences in prevalence can be also attributed to disparity due to differences in methodology, such as small sample sizes [ 35 – 38 , 41 – 43 , 45 , 48 ], large sample sizes [ 32 , 46 , 47 , 49 , 53 ], age groups (risk of disease increasing with advanced age) [ 36 ], sex differences in samples (certain diseases have more predilection according to sex) [ 35 ], and type of dental disease patients seeking treatment (periodontitis being more common is the most often sought treatment among all age groups) [ 55 ].…”