Coffee consumption and overall and cause-specific mortality: the Norwegian Women and Cancer Study (NOWAC)
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MORTALITY
Coffee consumption and overall and cause‑specific mortality: the Norwegian Women and Cancer Study (NOWAC) Marko Lukic1,2 · Runa Borgund Barnung1 · Guri Skeie1 · Karina Standahl Olsen1 · Tonje Braaten1 Received: 11 March 2020 / Accepted: 15 July 2020 © The Author(s) 2020
Abstract Coffee consumption has previously been reported to reduce overall and cause-specific mortality. We aimed to further investigate this association by coffee brewing methods and in a population with heavy coffee consumers. The information on total, filtered, instant, and boiled coffee consumption from self-administered questionnaires was available from 117,228 women in the Norwegian Women and Cancer (NOWAC) Study. We used flexible parametric survival models to calculate hazard ratios (HR) and 95% confidence intervals (CI) for all-cause, cardiovascular, and cancer mortality by total coffee consumption and brewing methods, and adjusted for smoking status, number of pack-years, age at smoking initiation, alcohol consumption, body mass index, physical activity, and duration of education. During 3.2 million person-years of follow-up, a total of 16,106 deaths occurred. Compared to light coffee consumers (≤ 1 cup/day), we found a statistically significant inverse association with high-moderate total coffee consumption (more than 4 and up to 6 cups/day, HR 0.89; 95% CI 0.83–0.94) and all-cause mortality. The adverse association between heavy filtered coffee consumption (> 6 cups/day) and all-cause mortality observed in the entire sample (HR 1.09; 95% CI 1.01–1.17) was not found in never smokers (HR 0.85; 95% CI 0.70–1.05). During the follow-up, both high-moderate total and filtered coffee consumption were inversely associated with the risk of cardiovascular mortality (HR 0.79; 95% CI 0.67–0.94; HR 0.80; 95% CI 0.67–0.94, respectively). The association was stronger in the analyses of never smokers (> 6 cups of filtered coffee/day HR 0.20; 95% CI 0.08–0.56). The consumption of more than 6 cups/day of filtered, instant, and coffee overall was found to increase the risk of cancer deaths during the follow-up. However, these associations were not statistically significant in the subgroup analyses of never smokers. The data from the NOWAC study indicate that the consumption of filtered coffee reduces the risk of cardiovascular deaths. The observed adverse association between coffee consumption and cancer mortality is most likely due to residual confounding by smoking. Keywords Coffee · Mortality · Cancer mortality · Cardiovascular mortality · Prospective cohort study
Introduction Average consumption of coffee in Norway reached almost 10 kg per capita during the previous decade [1]. Filtered coffee continues to be the most popular brewing method, Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10654-020-00664-x) contains supplementary material, which is available to authorized users. * Marko Lukic [email protected] 1
Department of Community Medicine, Faculty of Health Sciences, UiT The Ar
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