Morbidity and mortality of elderly patients with zoonotic Salmonella and Campylobacter: a population-based study.

Objectives: To evaluate the impact of age and comorbidity on the risk and prognosis of zoonotic Salmonella and Campylobacter gastroenteritis in elderly individuals.

Methods: Registry-based study comprising all first-time zoonotic Salmonella/Campylobacter gastroenteritis infections in two Danish counties from 1991 through 2003. Cases were elderly (>or=65 years) Salmonella/Campylobacter patients. Younger Salmonella/Campylobacter patients and age and gender matched individuals were reference persons.

Results: There were 13,324 Salmonella/Campylobacter patients (including 1226 elderly patients) and 26,648 matched reference persons. Elderly Salmonella/Campylobacter patients had more comorbidity than their matched reference persons (OR [95% CI]: 1.56 [1.35-1.80]) and comorbidity adjusted mortality rate ratios (95% CI) were 11.4 (5.1-25.4), 1.9 (1.4-2.6), and 1.3 (0.9-1.9) at day 0-30, 31-180, and 181-365, respectively. The differences in crude 365-day mortality increased with age when Salmonella/Campylobacter patients and reference persons without comorbidity were compared. The independent impact of age was less clear for individuals with comorbidity. There were no differences in comorbidity or survival between non-hospitalized elderly patients and their matched reference persons.

Conclusions: Elderly hospitalized Salmonella/Campylobacter patients had higher comorbidity and 1-year mortality than the background population. The excess 30-day mortality elucidated the prognostic role of the Salmonella/Campylobacter infection per se.