Analysis of 3 years of data showed that the incidence and incidence density of HAIs in elderly patients were significantly higher than in non-elderly patients (2.6% vs. 1.5%, 2.8/1000 d vs. 1.8/1000 d, P < 0.05). The incidence of HAIs in the oldest group (≥80 years) was three-fold higher than that in non-elderly (4.8% vs. 1.5%, P < 0.05). Although the incidence of HAIs in this study was lower than most previous publications, the trend was consistent. HAIs accounts for 3.5–9% of all infections in developed and developing countries [13]. Extensive studies in the USA and Europe showed that HAI incidence density ranged from 13.0 to 20.3 episodes per 1000 patient-days [14]. Incidence rates are higher in ICUs, affecting ~ 30% of patients [15]. However, a survey of long-term care facilities for the elderly in Japan found that the overall incidence rate of HAIs was 0.18 per 1000 resident-days [16]. A survey of the prevalence of HAIs in older people in acute care hospitals in Scotland found a linear relationship between HAI prevalence and increasing age, the incidence of HAIs in patients younger and older than 65 were 7.37 and 11.13%, respectively [13]. An investigation of the HAI incidence in elderly hospitalized patients at a hospital in Hunan Province, China reported that the HAI incidence in patients aged ≥65 was significantly higher than in those aged < 65 (3.53% vs. 0.98%, χ2 = 354.44, P < 0.001) [17]. We may have underestimated the HAI incidence because we did not implement post-discharge surveillance for all inpatients. The lower HAI incidence may also be related to the shorter average hospital stay. In this study, the median lengths were only 7 days overall and 8 days for elderly patients.
Elderly inpatients are at high risk of HAI because of their poor immune function, decreased mobility, and comorbid chronic noncommunicable diseases such as cardiovascular disease, cancer, diabetes, and chronic obstructive pulmonary disease (COPD). Furthermore, elderly inpatients with HAIs have poor prognosis and increased economic burden [18]. One study evaluated elderly patients who had an HAI in the ICU and found that clinical outcomes of the elderly who acquired an infection in the ICU were influenced by sociodemographic and clinical variables that increase mortality rates [19]. Another study of HAI in elderly patients identified the following risk factors: advanced age; comorbid neurological and chronic noncommunicable diseases such as cerebral hemorrhage, cerebral infarction, brain neoplasms, diabetes mellitus, coronary artery disease, malignant tumor and malignant hematonosis; hospital days before HAI; ICU admission; and device use [9]. The participants of that study were elderly ≥60 years with or without HAIs. To control for confounders and identify novel risk factors of HAI in this population, we investigated comorbidities and special medical procedures in elderly and non-elderly groups. The percentages of male patients, patients with comorbidities (e.g., cerebrovascular disease, brain neoplasms, hypertension, hyperlipidemia, diabetes mellitus, coronary artery disease, COPD, malignant tumor, malignant hematonosis, and osteoarthropathy), and ICU admissions were significantly higher in the elderly group. Conversely, fewer elderly patients underwent surgery lower. These results suggest that the higher incidence of HAI in elderly may be attributable to the higher rates of comorbidities and special medical procedures in elderly inpatients.
One of the primary concerns of the current investigation was identifying common HAIs sites in elderly inpatients. Most HAIs were found in the lower respiratory tract, urinary system, and bloodstream. These findings are consistent with other available studies of both elderly and non-elderly inpatients [11, 20]. With recent improvements in implants, it is important to focus on device-associated infections (DAIs). The International Nosocomial Infection Control Consortium (INICC) and National Healthcare Safety Network reported monitoring data of HAIs in general and DAIs in particular. The INICC recorded the data of 861,284 patients hospitalized in INICC hospital ICUs in 50 countries for an aggregate of 3,506,562 days from 2010 to 2015. There were 6.2–19.2 cases of VAP per 1000 mechanical ventilator-days, 1.44–10.14 CLABSIs per 1000 central line-days, and 1.66–17.17 CAUTIs per 1000 catheter-days [21].
For elderly inpatients with lower respiratory tract, urinary system, and bloodstream infections, the percentages of VAP, CAUTI, and CLABSI were 7.1% (57/802), 61.4% (170/277), and 33.3% (90/270), respectively. Ventilator and central line use rates in the elderly group were significantly higher than in the non-elderly, but the elderly had a lower urinary catheter use rate. The incidence density of VAP in elderly was lower than in non-elderly, but CAUTIs were significantly higher, and CLABSI rates were similar. These results suggest that the incidence densities of VAP, CLABSI, and CAUTI in elderly inpatients did not increase with the ventilator, central line, and urinary catheter use rates. The lower incidence density of VAP in the elderly group was probably because the admitting diagnosis often included lower respiratory tract infections, and it was difficult to find evidence of VAP in these patients. The high incidence density of CAUTI in elderly inpatients is consistent with other reports. A study concerned with risk factors for CAUTI in Italian elderly found that increasing age and duration of hospital stay before catheter insertion were associated with CAUTIs [22]. The high percentage of CAUTI may be related to specific issues of elderly inpatients, but also due to failures in catheter insertion as we observed here and which may be our next study. The low similar incidence density of CLABSI in both the elderly and non-elderly groups may be related to effective interventions to prevent CLABSI. Hallam and colleagues collected data over a 5-year period and found a significant and sustained reduction in the CLABSI rate from 5 per 1000 catheter days to 0.23 per 1000 catheter days [23].
The other notable finding of the current investigation was the pathogens detected in elderly HAI patients. The five most common were Candida albicans, Klebsiella pneumonia, Acinetobacter baumannii, Escherichia coli, and Pseudomonas aeruginosa, but they varied by infection site. Extensive use of broad-spectrum antibiotics in elderly could account for the high positive detection rate of Candida albicans. The main pathogens of lower respiratory tract, urinary system, and bloodstream infections detected in elderly HAI patients could serve as reference evidence for empirical use of antibiotics to treat HAIs.
Study limitations
First, this was a single-center study, so our findings cannot be generalized to all elderly patients in China. Second, we may have underestimated the HAI incidence because we did not implement post-discharge surveillance for all inpatients. Finally, the microorganism profile did not include drug sensitivity or antibiotic resistance. We will include those tests in our next study to better prevent HAIs in elderly inpatients.
