Long-term mortality after poliomyelitis.

Background: Few studies have described mortality and cause of death among persons with a history of polio.

Methods: We identified a group of patients diagnosed with poliomyelitis in Copenhagen between 1919 and 1954. We obtained information on vital status through May 1997 and on cause of death by linkage with the Danish Civil Registration System and the Danish Cause-of-Death Register. Overall and cause-specific standardized mortality ratios served as the measure of mortality risk relative to that of the general population.

Results: We observed 1295 deaths among 5977 polio patients compared with an expected 1141 deaths (standardized mortality ratio = 1.14; 95% confidence interval = 1.07-1.20). Excess mortality was restricted to polio patients with a history of severe paralysis of the extremities (1.69; 1.32-2.15) or patients who had been treated for respiratory failure during the epidemics (2.71; 2.18-3.37). Apart from polio patients with respiratory failure, long-term mortality did not appear to increase until 20 years after discharge. Contracting severe paralytic poliomyelitis at a young age seemed to increase long-term mortality. The most common causes of death were polio sequelae (standardized mortality ratio = 141; 95% confidence interval = 98-203), respiratory tract diseases (1.38; 1.13-1.69), breast cancer (1.40; 1.06-1.85), gastrointestinal diseases (1.44; 1.14-1.82) and suicide (1.53; 1.25-1.86). Except for polio sequelae, causes of death did not differ between paralytic and nonparalytic polio patients.

Conclusions: Survivors of poliomyelitis, especially severely paralyzed polio patients, have an increased long-term mortality.