Study shows higher coffee consumption was associated with a lower risk of prostate cancer

Prostate cancer is the second most frequently diagnosed cancer and the sixth leading cause of cancer death in men. There were 1 276 000 new cancer cases and 359 000 cancer deaths in 2018. It is estimated that nearly three-quarters of prostate cancer cases occur in developed countries. Since the 1970s, the incidence of prostate cancer has also increased rapidly in some Asian countries such as China, Singapore and Japan, where the incidence has always been much lower than in some Western countries. Therefore, primary prevention of prostate cancer is a significant public health problem worldwide.

Coffee is one of the most popular beverages. Since its popularity continues to increase worldwide, even a small effect on individual health may exert a substantial public health impact. Coffee is known to be a major source of dietary caffeine, cafestol and antioxidants in industrialised nations. Its various constituents such as caffeine, caffeic acid and chlorogenic acid can potentially impact the development of cancer through multiple carcinogenesis pathways. Inverse associations were observed between coffee consumption and the risk of cancer in sites such as the liver, colorectum and breast. However, previous studies have reported inconsistent results on the association of coffee consumption with the risk of prostate cancer. Although earlier cohort studies did not detect an association, more recent studies conducted in major Western countries such as the USA, Sweden and the UK reported that coffee consumption was associated with a lower risk of localised and advanced prostate cancer. In Japan, a country with increasing popularity of coffee, a cohort study also found a significant inverse association between coffee consumption and the risk of prostate cancer.

Previous meta-analyses of cohort studies up to 2015 reported a significant positive association for coffee consumption on total prostate cancer risk, with highly variable results in different subgroups. Since then, five cohort studies have explored the association but still reported inconsistent results. It was hypothesised that higher coffee consumption was associated with an increased risk of prostate cancer. Thus, the objective of this updated meta-analysis was to explore and evaluate the association of coffee intake with the risk of prostate cancer in adult men, and to direct the future primary prevention strategy on prostate cancer.

Researchers identified 497 records after searching the three databases. After 217 duplicate records were removed, 280 records remained for screening of titles and abstracts, and after screening the titles and abstracts, 254 irrelevant records were excluded. Following a further full-text review of the 26 remaining studies, 10 studies were excluded because of no useful risk estimates or 95% CIs; two studies were excluded as newer data or more informative data were available. Fourteen studies were obtained from full-text screening and a further two studies were identified by checking the reference lists of retrieved articles. Thus, 16 studies were included in the final analysis, of which 15 reported on the risk of prostate cancer associated with the highest versus the lowest coffee consumption; 13 studies reported the risk associated with an increase of one cup of coffee per day or provided sufficient data to estimate the dose–response risk.

The Result

 Sixteen prospective cohort studies were finally included, with 57 732 cases of prostate cancer and 1 081 586 total cohort members. Higher coffee consumption was significantly associated with a lower risk of prostate cancer. Compared with the lowest category of coffee consumption, the pooled relative risk (RR) was 0.91 (95% CI 0.84 to 0.98), I²= 53.2%) for the highest category of coffee consumption. There was a significant linear trend for the association (p=0.006 for linear trend), with a pooled RR of 0.988 (95% CI 0.981 to 0.995) for each increment of one cup of coffee per day. For localised, advanced and fatal prostate cancer, the pooled RRs were 0.93 (95% CI 0.87 to 0.99), 0.88 (95% CI 0.71 to 1.09) and 0.84 (95% CI 0.66 to 1.08), respectively. No evidence of publication bias was indicated in this meta-analysis.

 This study suggests that a higher intake of coffee may be associated with a lower risk of prostate cancer.

Source: BMJ (CC BY-NC 4.0)