Life-long morbidity among Danes with poliomyelitis

To estimate long-term morbidity in a cohort of Danish poliomyelitis patients.

A historical prospective cohort study of 27,047 persons.

Denmark.

A total of 5421 persons hospitalized for poliomyelitis between 1919 to 1954 in Copenhagen, Denmark, and 21,626 age- and gender-matched Danes. Participants were followed up on average for 20.6 years, yielding a total of 555,884 person-years of follow-up.

Not applicable.

The exposed (poliomyelitis) cohort and the unexposed (control) cohort were followed up for somatic hospitalization from 1977 to 1999 in the Danish Hospital Discharge Register. The incidence rate ratio (IRR) was calculated as the ratio between the incidence rate of disease in the exposed and unexposed cohorts.

Overall, polio patients had a 1.2- to 1.3-fold increased risk of being hospitalized with pulmonary diseases, heart diseases, gastrointestinal disorders, or diseases of the locomotive apparatus. Among paralytic polio patients, long-term morbidity seems to be associated with the acute severity of poliomyelitis, as well as young age at infection. Paralytic patients, who contracted respiratory polio under the age of 5, had the highest risk of being hospitalized with lung diseases (IRR=7.26; 95% confidence interval [CI], 3.06-18.33), diseases of the locomotive apparatus (IRR=4.05; 95% CI, 1.66-9.86), heart diseases (IRR=1.70; 95% CI, 0.65-3.98), and diseases of the digestive system (IRR= 2.23; 95% CI, 1.03-4.62). Surprisingly, patients without paralyses, especially women, also had an increased morbidity.

Overall, a history of poliomyelitis was associated with a slightly increased morbidity measured by hospitalizations. Long-term morbidity was highest among respiratory polio patients; however, patients presumably left without any residual symptoms also had an increased morbidity.