Table 1.

Obesity and the incidence of bladder cancer.

Study Author	Study Year	Total No. of Patients	Total No. of Studies	Study Type	Comments
Qin et al. [21]	2013	8,718,502	11 (includes studies A–J)	Meta-analysis of cohort studies	“When stratifying by gender, the summary RRs with 95% CIs were 1.10 (95% CI 1.05–1.16; p = 0.334 for heterogeneity; I2 =12.3%) for male, and 1.15 (95% CI 1.02–1.29; p = 0.190 for heterogeneity; I2 =29.8%) for female”. “Among the 9 studies that controlled for cigarette smoking, the pooled RR was 1.09 (95% CI 1.01–1.17; p = 0.131 for heterogeneity; I2 = 35.9%)”.
Noguchi et al. [19]	2015	8,920,237	16 (includes studies A–F, and I–K)	Review	“The single largest study identified a null association of obesity with bladder cancer incidence”.
Stewart et al. [22]	2011	Not applicable	N/A	Review	“Although, a relationship between obesity and the natural course of bladder cancer may be present, due to the mixed and minimal observations within the literature, no firm conclusions can be drawn at this time”.
Zhao et al. [23]	2017	5,640,760	14 (includes studies A–K)	Meta-analysis	“There was evidence of heterogeneity among studies for obesity category (p = 0.003, I2 = 58.5%)”.
Sun et al. [18]	2015	14,201,500	15 (includes studies A–H, J, and K)	Meta-analysis of cohort studies	“Stronger associations between BMI and bladder cancer risk were found if BMI was assessed by self-reported, and if the average age of participants was greater than 50 years old. No significant effect differences were observed for duration of follow-up and for the gender of participants”.
Eggers et al. [24]	2013	Not applicable	N/A	Review	“Conflicting literature points to an unclear, but possible relation between obesity and bladder tumors”.

A = Haggstrom et al., 2011, B = Keobinck et al., 2008, C = Larsson et al., 2008, D = Semanic et al., 2006, E = Holick et al., 2006, F = Tripathi et al., 2002, G = Jee et al., 2008, H = Reeves et al., 2007, I = Cantwell et al., 2006, J = Wolk et al., 2001, and K = Rapp et al., 2005.