Month) vs. no use Regular use ( 2 times a week) vs. no use Regular use (.2 times a week) vs. no use Regular use (daily use) vs. no use Regular use (.1 tine a week for 1 year) vs. no use 10781694 Regular use ( 2 times a week for 1 month) vs. no useNSAIDs Use and Bladder Cancer RiskFigure 2. Risk estimates of bladder cancer associated with regular/any use of acetaminophen. Squares indicate study-specific risk estimates (size of the square reflects the study-specific statistical weight, i.e., the inverse of the variance); horizontal lines indicate 95 confidence intervals (CIs); diamonds indicate summary risk estimate with its corresponding 95 confidence interval. doi:10.1371/journal.pone.0070008.gLaird random-effects model, which considers both within- and between-study variations [12]. Statistical heterogeneity among studies was assessed using the Cochrane’s Q statistic, and inconsistency was quantified with the I2 statistic that estimates the percentage of total variation across studies due to heterogeneity rather than chance [13]. For the Q statistic, a P value ,0.10 was considered statistically significant for heterogeneity; for I2, a value .50 is considered a measure of severe heterogeneity. When statistical heterogeneity was detected, sensitivity analyses were performed. Publication bias was evaluated with Egger’s regression test in which P value less than 0.10 was considered representative of statistically significant publication bias [14]. All statistical analyses were performed with Stata 10 software (Stata Corporation, College Station, Texas). We performed this meta-analysis in accordance with the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement [15].Results Literature SearchThe detailed steps of our literature search are shown in Figure 1. Briefly, our initial search strategy retrieved a total of 363 citations. After the titles and abstracts were screened, 339 articles were excluded En to a computer-assisted data acquisition system CED 1401 data processor (CED because they were laboratory studies, review articles, or irrelevant to the current study. We identified 24 potentiallyrelevant articles. Three articles were excluded because they reported on similar population [16?8]. Two publications were excluded because there were no outcomes of bladder cancer [19,20], one was excluded because it did not provide RR estimate [21] and the remaining one was excluded because it did not report analgesics use of our interest [22]. Finally, 17 articles [23?9] were included in this meta-analysis (Figure 1). The 17 relevant studies were published between 1985 and 2012, including 8 cohort studies [28?1,35?8] and 9 case-control studies [23?7,32?4,39]. A total of 1,008,800 participants, including 10,618 bladder cancer cases were involved in these studies and followed for 3?1 years. Ten studies were used for analysis of Title Loaded From File acetaminophen use [23?8,33?5,39], 11 for aspirin use [25,26,29,31,33?9] and 6 for non-aspirin NSAIDs use [30,32,33,36,38,39]. The characteristics of the included studies for the 3 most commonly used analgesics are summarized in Table 1. Most studies provided risk estimates that were adjusted for age (16 studies), sex (14 studies) and smoking (12 studies); fewer were adjusted for race (6 studies), body mass index (4 studies), and education (4 studies). The exposure definitions of the included studies are shown in Table 2.AcetaminophenThe multivariable-adjusted RRs of bladder cancer for regular/ any use of acetaminophen in individual observational studies and su.Month) vs. no use Regular use ( 2 times a week) vs. no use Regular use (.2 times a week) vs. no use Regular use (daily use) vs. no use Regular use (.1 tine a week for 1 year) vs. no use 10781694 Regular use ( 2 times a week for 1 month) vs. no useNSAIDs Use and Bladder Cancer RiskFigure 2. Risk estimates of bladder cancer associated with regular/any use of acetaminophen. Squares indicate study-specific risk estimates (size of the square reflects the study-specific statistical weight, i.e., the inverse of the variance); horizontal lines indicate 95 confidence intervals (CIs); diamonds indicate summary risk estimate with its corresponding 95 confidence interval. doi:10.1371/journal.pone.0070008.gLaird random-effects model, which considers both within- and between-study variations [12]. Statistical heterogeneity among studies was assessed using the Cochrane’s Q statistic, and inconsistency was quantified with the I2 statistic that estimates the percentage of total variation across studies due to heterogeneity rather than chance [13]. For the Q statistic, a P value ,0.10 was considered statistically significant for heterogeneity; for I2, a value .50 is considered a measure of severe heterogeneity. When statistical heterogeneity was detected, sensitivity analyses were performed. Publication bias was evaluated with Egger’s regression test in which P value less than 0.10 was considered representative of statistically significant publication bias [14]. All statistical analyses were performed with Stata 10 software (Stata Corporation, College Station, Texas). We performed this meta-analysis in accordance with the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement [15].Results Literature SearchThe detailed steps of our literature search are shown in Figure 1. Briefly, our initial search strategy retrieved a total of 363 citations. After the titles and abstracts were screened, 339 articles were excluded because they were laboratory studies, review articles, or irrelevant to the current study. We identified 24 potentiallyrelevant articles. Three articles were excluded because they reported on similar population [16?8]. Two publications were excluded because there were no outcomes of bladder cancer [19,20], one was excluded because it did not provide RR estimate [21] and the remaining one was excluded because it did not report analgesics use of our interest [22]. Finally, 17 articles [23?9] were included in this meta-analysis (Figure 1). The 17 relevant studies were published between 1985 and 2012, including 8 cohort studies [28?1,35?8] and 9 case-control studies [23?7,32?4,39]. A total of 1,008,800 participants, including 10,618 bladder cancer cases were involved in these studies and followed for 3?1 years. Ten studies were used for analysis of acetaminophen use [23?8,33?5,39], 11 for aspirin use [25,26,29,31,33?9] and 6 for non-aspirin NSAIDs use [30,32,33,36,38,39]. The characteristics of the included studies for the 3 most commonly used analgesics are summarized in Table 1. Most studies provided risk estimates that were adjusted for age (16 studies), sex (14 studies) and smoking (12 studies); fewer were adjusted for race (6 studies), body mass index (4 studies), and education (4 studies). The exposure definitions of the included studies are shown in Table 2.AcetaminophenThe multivariable-adjusted RRs of bladder cancer for regular/ any use of acetaminophen in individual observational studies and su.
