Background: Patients who are hospitalized for pneumonia have an increased incidence of lung cancer compared with the general population. We have investigated the incidence of lung cancer among 7044 patients hospitalised for pneumonia. The objective of the study was to identify determinants of lung cancer.
Methods: We have conducted a nested patient-control study. The source population consisted of patients hospitalised for pneumonia (N=7044) at Akershus University Hospital in the period 1-Jan-1988 to 31-Dec-2002. Until 31-Dec-2005 189 of these patients developed lung cancer, and constitute our index group. A random sample of 198 pneumonia patients, constitute our control group. For both groups, smoking habits and spirometry data were collected from the patient’s medical record. Confirmation of lung cancer diagnosis was collected from the Cancer Registry of Norway.
Results: Total observation time of the source population was 32,3 years, and the median follow-up time was 3.8 years. The mean age at the time of pneumonia was 68 and 64 years in those who developed cancer and the references, respectively. The number of females was 57 (30 %) in the index group, and 92 (46 %) among the references. Spirometry data was available only in 194 patients (51 %). Multiple logistic regression showed that males, bronchial obstruction and date of birth prior to 1940 were associated with increased incidence of lung cancer. 32,4 % of the patients had a cumulative risk less than 1 %.
Conclusions: We have found that obstructive, males born before 1940 constitute a high risk group of lung cancer after pneumonia, and that risk stratification regarding lung cancer after pneumonia is possible. Prospective studies are, however, needed.