30 However, confounding by unmeasured variables and residual confounding might have affected the results PR-171 of this observational study. Since we were unable to identify conditions managed only by a patient’s

GP, the prevalence values for hypertension, obesity and alcoholism are most likely underestimated in our study. Interpretation To the best of our knowledge, this study was the first to examine the effect of pre-existing AF and its treatment on the prognosis for pneumonia patients. This study added to previous studies reporting a high risk of thromboembolic complications and mortality in pneumonia patients.7 11 Our results indicated that there was a similar adjusted risk of arterial thromboembolism and an equal adjusted mortality in hospitalised pneumonia patients with and without AF, after confounders were accounted for. We also did not find that there were different rates in ICU admission or treatment with mechanical ventilation for patients with AF compared with patients without AF. Our finding of similar prognosis in pneumonia patients with and without pre-existing AF conflicts with previous findings of increased mortality in pneumonia patients with new-onset AF.9 We can only speculate on the mechanisms behind this difference,

yet as opposed to patients with new-onset AF, patients with pre-existing AF are more likely to receive well-balanced treatment for AF at the time of pneumonia; possibly, current management approaches can counterbalance the potentially deleterious effects of AF. Indeed, we have shown that preadmission medical treatment for AF appears to have great prognostic impact in pneumonia patients with this condition. Alternatively, new-onset AF during pneumonia may not be associated with worse prognosis per se, but rather

is a marker of clinically more severe pneumonia. Our study adds to the growing number of observational studies that support a protective role for the preadmission use of statins in hospitalised pneumonia patients. Our Brefeldin_A findings for the prognostic effect measures of statin therapy are comparable to previously published findings.18 31–34 We also found that there was a substantial beneficial effect of β-blocker therapy in pneumonia patients with AF. β-blockers may improve the prognosis for pneumonia patients with AF by protecting against uncontrolled tachycardia and reducing myocardial oxygen consumption. In patients with paroxysmal AF, β-blockers could protect against AF relapse provoked by increased sympathetic tonus. β-blockers can also dampen the metabolic changes towards catabolism that occur during critical illness.35 Pre-admission β-blocker use was also related to improved prognosis in patients without AF indicating that the beneficial effects of β-blockers are not exclusive to patients with AF.