Higher Caffeinated Coffee Intake Is Associated with Reduced Malignant Melanoma Risk: A Meta-Analysis Study

Abstract

Background: Several epidemiological studies have determined the associations between coffee intake level and skin cancer risk; however, the results were not yet conclusive. Herein, we conducted a systematic review and meta-analysis of the cohort and case-control studies for the association between coffee intake level and malignant melanoma (MM) risk.

Methods: Studies were identified through searching the PubMed and MEDLINE databases (to November, 2015). Study-specific risk estimates were pooled under the random-effects model.

Results: Two case-control studies (846 MM patients and 843 controls) and five cohort studies (including 844,246 participants and 5,737 MM cases) were identified. For caffeinated coffee, the pooled relative risk (RR) of MM was 0.81 [95% confidential interval (95% CI) = 0.68-0.97; P-value for Q-test = 0.003; I2 = 63.5%] for those with highest versus lowest quantity of intake. In the dose-response analysis, the RR of MM was 0.955 (95% CI = 0.912-0.999) for per 1 cup/day increment of caffeinated coffee consumption and linearity dose-response association was found (P-value for nonlinearity = 0.326). Strikingly, no significant association was found between the decaffeinated coffee intake level and MM risk (pooled RR = 0.92, 95% CI = 0.81-1.05; P-value for Q-test = 0.967; I2 = 0%; highest versus lowest quantity of intake).

Conclusions: This meta-analysis suggested that caffeinated coffee might have chemo-preventive effects against MM but not decaffeinated coffee. However, larger prospective studies and the intervention studies are warranted to confirm these findings.

Fig 1. The working flow chart for eligible study identification in meta-analysis studies.

Fig 2. The relative risks (RRs) of melanoma for the highest versus lowest quantity of caffeinated coffee intake in case-control studies and cohort studies.

The square represents the study-specific RR and the size of the squares reflects the statistical weight in the meta-analysis; horizontal lines represent the 95% confidential intervals (95% CIs); the diamond indicates the overall RR with its 95% CI under the random-effects model.

Fig 3. The dose-relationship between the caffeinated coffee intake (cups/day) and the MM risk compared to non-drinkers (P for non-linearity = 0.326).

Fig 4. The relative risks (RRs) of melanoma for the highest versus lowest quantity of decaffeinated coffee intake in case-control studies and cohort studies.

The square represents the study-specific RR and the size of the squares reflects the statistical weight in the meta-analysis; horizontal lines represent the 95% confidential intervals (95% CIs); the diamond indicates the overall RR with its 95% CI under the random-effects model.