Effect of Pneumonia on All-cause Mortality after Elderly Hip Fracture: a Korean Nationwide Cohort Study

BACKGROUND: The purposes of this study were 1) to investigate the incidence of pneumonia during hospitalization in elderly hip fracture patients, 2) to evaluate the effect of pneumonia on 30 day to 1 year mortality and 3) to analyze the impact of age and gender on the mortality rate in the pneumonia patients using a nationwide cohort of Korea. METHODS: The Korean National Health Insurance Service (NHIS) database included approximately 5.5 million Korean enrollees > 60 years of age. A total of 588,147 participants were randomly selected for senior cohort using 10% simple random sampling. We identified senile (> 65 years old) patients who underwent hip fracture surgery from January 2005 to December 2014 and those who developed pneumonia during hospitalization from the NHIS-Senior cohort. The index date of hip fracture occurrence was defined as the date of admission to the acute care hospital. The last date of follow-up was defined as the date of death or 31 December 2015, whichever came first. A multivariable-adjusted Cox proportional hazards model was used to investigate the effects of pneumonia on all-cause mortality. RESULTS: During the enrollment period, a total of 14,736 patients, who were older than 65 years, underwent hip fracture surgeries. Among them, 1,629 patients (11.05%) developed pneumonia during the hospitalization. The pneumonia incidence was 16.39% (601/3,666) in men patients and 9.29% (1,028/10,042) in women patients. Compared to 13,107 non-pneumonia patients, adjusted relative risk (aRR) of death in pneumonia patients was 2.69 (95% confidence interval [CI], 2.14–3.38; P < 0.001) within postoperative 30-day, 3.40 (95% CI, 3.01–3.83; P < 0.001) within postoperative 90-day, 2.86 (95% CI, 2.61–3.15; P < 0.001) within postoperative 180-day and 2.31 (95% CI, 2.14–2.50; P < 0.001) within postoperative 1-year. According to patient's age, the aRR of death in pneumonia patients was 5.75 (95% CI, 2.89–11.43) in adults aged < 70 years, 5.14 (95% CI, 4.08–6.46) in those aged 70–79 years, 3.29 (95% CI, 2.81–3.86) in those aged 80–89 years and 2.02 (95% CI, 1.52–2.69) in those aged ≥ 90 years. The aRR was 3.63 (95% CI, 3.01–4.38) in men pneumonia patients, and 3.27 (95% CI, 2.80–3.83) in women pneumonia patients. CONCLUSION: The prevalence of pneumonia in elderly hip fracture patients was 11.05%. Men had higher incidence (16.39%) than women (9.29%). Compared to non-pneumonia patients, the pneumonia patients had higher 30-day to 1-year mortalities with aRR of 2.31 to 3.40. They had increased mortality in all age groups older than 65 years with aRR of 1.52 to 4.08. Both genders of pneumonia patients had higher risk of mortality (aRR, 3.63 in men and 3.27 in women) compared to non-pneumonia patients.