BackgroundAtrial fibrillation (AF) and cancer are frequent diseases worldwide. The timewise association between the diagnosis of AF and a subsequent diagnosis of cancer may clarify whether a mutual cause exists, and may also guide clinicians about time windows of high risk of cancer occurrence.Methods and ResultsWe conducted a population‐based cohort study among 26 222 men and 28 879 women free of AF and cancer at baseline based on the Danish Diet, Cancer and Health study. The participants were followed for the development of AF (the Danish National Patient Registry) and subsequent cancer (the Danish Cancer Registry) until 2013. We used Cox proportional hazard models with new‐onset AF as time‐dependent exposure. The men (median age 56 years) and women (median age 56 years) were followed for medians of 16.7 and 19.6 years, respectively. AF was associated with higher risks of any type of cancer (men: hazard ratio [HR] 1.41, 95% confidence interval [CI], 1.26–1.58; women: HR 1.15, 95% CI, 1.02–1.32), and for men only, lung (HR 1.66, 95% CI, 1.19–2.30), and colorectal cancer (HR 1.37, 95% CI, 1.02–1.85). Within the initial 90 days following the diagnosis of AF, the risks of any type of cancer (men: HR 2.89, 95% CI, 2.10–3.98; women: HR 3.72, 95% CI, 2.49–5.56), lung (men: HR 7.70, 95% CI, 4.34–13.68; women: HR 7.98, 95% CI, 3.96–16.09), and colorectal cancer (men: HR 3.35, 95% CI, 1.03–10.90; women: HR 5.91, 95% CI, 2.44–14.29) were higher for men and women.ConclusionsA diagnosis of AF is associated with a higher incidence rate of cancer among men and women. The cancer incidence rate is particularly elevated within 90 days after the diagnosis of AF.

ObjectiveTo assess temporal trends in the association between newly diagnosed atrial fibrillation and death.DesignCommunity based cohort study.SettingFramingham Heart Study cohort, in 1972-85, 1986-2000, and 2001-15 (periods 1-3, respectively), in Framingham, MA, USA.ParticipantsParticipants with no atrial fibrillation, aged 45-95 in each time period, and identified with newly diagnosed atrial fibrillation (or atrial flutter) during each time period.Main outcome measuresThe main outcome was all cause mortality. Hazard ratios for the association between time varying atrial fibrillation and all cause mortality were calculated with adjustment for time varying confounding factors. The difference in restricted mean survival times, adjusted for confounders, between participants with atrial fibrillation and matched referents at 10 years after a diagnosis of atrial fibrillation was estimated. Meta-regression was used to test for linear trends in hazard ratios and restricted mean survival times over the different time periods.Results5671 participants were selected in time period 1, 6177 in period 2, and 6174 in period 3. Adjusted hazard ratios for all cause mortality between participants with and without atrial fibrillation were 1.9 (95% confidence interval 1.7 to 2.2) in time period 1, 1.4 (1.3 to 1.6) in period 2, and 1.7 (1.5 to 2.0) in period 3 (Ptrend=0.70). Ten years after diagnosis of atrial fibrillation, the adjusted difference in restricted mean survival times between participants with atrial fibrillation and matched referents decreased by 31%, from −2.9 years (95% confidence interval −3.2 to −2.5) in period 1, to −2.1 years (−2.4 to −1.8) in period 2, to −2.0 years (−2.3 to −1.7) in period 3 (Ptrend=0.03).ConclusionsNo evidence of a temporal trend in hazard ratios for the association between atrial fibrillation and all cause mortality was found. The mean number of life years lost to atrial fibrillation at 10 years had improved significantly, but a two year gap compared with individuals without atrial fibrillation still remained.