Coffee consumption and bladder cancer: a meta-analysis of observational studies

Abstract

Controversial results of the association between coffee consumption and bladder cancer (BC) risk were reported among epidemiological studies. Therefore, we conducted this meta-analysis to clarify the association. Relevant studies were identified according to the inclusion criteria. Totally, 34 case-control studies and 6 cohort studies were included in our meta-analysis. The overall odds ratio (OR) with 95% confidence interval (CI) between coffee consumption and BC risk was 1.33 (95% CI 1.19 to 1.48). The summary ORs of BC for an increase of 1 cup of coffee per day were 1.05 (95% CI 1.03 to 1.06) for case-control studies and 1.03 (95% CI 0.99 to 1.06) for cohort studies. The overall ORs for male coffee drinkers, female coffee drinkers and coffee drinkers of both gender were 1.31 (95% CI: 1.08 to 1.59), 1.30 (95% CI: 0.87 to 1.96) and 1.35 (95% CI: 1.20 to 1.51). Compared with smokers (OR = 1.24, 95% CI: 0.91 to 1.70), non-smokers had a higher risk (OR = 1.72, 95% CI: 1.25 to 2.35) for BC. Results of this meta-analysis suggested that there was an increased risk between coffee consumption and BC. Male coffee drinkers and non-smoking coffee drinkers were more likely to develop BC.

The association between coffee consumption and bladder cancer incidence in a pooled analysis of the Miyagi Cohort Study and Ohsaki Cohort Study

“…All previous studies certainly adjusted for the amount of consumed cigarettes, a risk factor for bladder cancer (Zeegers et al, 2004). However, a meta-analysis found that the risk of bladder cancer according to coffee consumption was lower among smokers than nonsmokers (Wu et al, 2015). Therefore, underestimation of the interaction between coffee consumption and smoking might have occurred in the previous studies.…”

“…In summary, four studies reported a positive association (Mills et al, 1991;Chyou et al, 1993;Tripathi et al, 2002;Kurahashi et al, 2009), one a null association (Nagano et al, 2000), and two an inverse association (Michaud et al, 1999;Kurahashi et al, 2009), although none was statistically significant. In this context, a metaanalysis that included six of these cohort outcomes reported that coffee consumption was associated with an increased risk of bladder cancer (Zhou et al, 2012), whereas a more recent meta-analysis that included six different outcomes showed no association (Wu et al, 2015). However, the studies that showed a null or an increased risk of bladder cancer had certain limitations (< 18.5, 18.5-24.9, ≥ 25 kg/m 2 , or missing), history of hypertension, diabetes mellitus, myocardial infarction, stroke (for each disease; yes, no), job status (employed, not employed, or missing), years of education (< 16, 16-18.9, ≥ 19 years, or missing), smoking status (never, former, current smoker < 20 cigarettes/day, or current smoker ≥ 20 cigarettes/day, or missing), alcohol consumption (never, former, current, or missing), green tea consumption (< 1, 1-2, 3-4, ≥ 5 cups/day, or missing), and time spent walking (< 30 min/day, 30 min-1 h/day, > 1 h/day, or missing).…”

Coffee Consumption and the Risk of Thyroid Cancer: A Systematic Review and Meta-Analysis

“…However, hospital-based controls might alter their coffee consumption behavior according to their medical condition [25]. When considering the coffee is associated with health, hospital-based controls might overstate their actual coffee consumption more than population-based controls [26]. …”

Dietary Inflammatory Index and Risk of Bladder Cancer in a Large Italian Case-control Study

“…6, 7 Fruits and vegetables are rich in various vitamins such as thiamin, niacin, vitamin E and carotenoids, which have anti-inflammatory effects and therefore contribute to lower DII scores. 10 In a large European cohort study, consumption of carotenoids, such as beta-carotene, was found to reduce the risk of BC.…”

“…6, 7 Dietary patterns characterizing the Western-type diet; i.e., including high consumption of red meat, high-fat dairy products, and refined grains, have been associated with higher levels of c-reactive protein (CRP), interleukin-6 (IL-6), and fibrinogen. 8 On the other hand, the Mediterranean diet –characterized by a high consumption of whole-grains, fruit and green vegetables, fish, and olive oil, a low consumption of red meat and butter, and a moderate alcohol and dairy products consumption – has been associated with lower levels of inflammation.…”