Relationship Between Sleep Apnea and Respiratory Infections in BedRidden Elderly Individuals on Tube Feeding (2012)

Many of the elderly residents in long-term care facilities have difficulty swallowing and are at risk of acquiring lower respiratory tract infections. Although several effective prevention strategies have been developed, elderly adults frequently develop respiratory infections due to microaspiration.1, 2 The clarification of novel risk factors would be an important step toward the prevention of pneumonia in these individuals. The clinical importance of sleep apnea has already been established in younger adults,3, 4 but the prevalence and significance of sleep apnea has not been well investigated in bedridden elderly adults.5 A previous study showed that individuals with sleep apnea syndrome (SAS) were likely to have an impaired swallowing reflex.6 The current study was performed to test the hypothesis that sleep-related breathing disorders are related to the incidence of respiratory infections. Forty consecutive bedridden elderly adults without oral intake admitted to Okamoto-Ishii Hospital more than 90 days before they were recruited from the long-term care ward. The care need levels of the individuals were classified following the system approved by the public long-term care insurance system in Japan.7 In this system, individuals are categorized as requiring care levels from 1 (requiring support for walking) to 5 (requiring care for every activity) according to the public criteria for long-term care requirements. The institutional review board of the Graduate School of Medicine, University of Tokyo, approved the study protocol. Sleep respiratory parameters were measured using a portable sleep monitoring device from 8 p.m. to 6 a.m. The apnea–hypopnea index (AHI) was calculated as the number of apneas and hypopneas per hour, and the oxygen desaturation index (ODI) was calculated as the frequency of a decrease in the arterial blood oxygen saturation of more than 3% per hour. The severity of sleep apnea syndrome was classified according to AHI as mild (5–15), moderate (16–30) and severe (>30).8 The past 90-day records of daily morning axillary temperatures and the clinical diagnosis by each attending physician were obtained for all of the enrolled individuals. Definite lower respiratory tract infections had been determined using the combination of physical examinations, blood examinations, chest X-rays, and chest computed tomography. Fever due to probable respiratory infections was determined by excluding the fevers diagnosed as resulting from other infections. The duration of febrile days due to probable respiratory infections of 37.0°C or greater, 37.5°C or greater, and 38.0°C or greater in each individual were calculated. All of the patients were bedridden elderly adults with a high level of care need (level 4, 7.5%; level 5, 92.5%). Mean age was 82.5 ± 8.0 and mean body mass index was 16.6 ± 3.0 kg/m.2 Thirty-six patients (90.0%) had more than five events/hour according to their AHI, corresponding to the diagnostic criteria for SAS. Eleven patients (27.5%) had mild SAS, 14 (35.0%) had moderate SAS, and 11 (27.5%) had severe SAS. Logistic regression analysis showed that a higher AHI was independently associated with a history of lower respiratory tract infections after adjusting for other variables (P = .004) (Table 1). The median duration of febrile days due to probable respiratory infections was 16.5 days for 37.0°C or greater, 6.0 days for 37.5°C or greater, and 2.0 days for ≥ 38.0°C or greater. The duration of febrile days of 38.0°C or greater was significantly correlated with AHI (P < .001) and ODI (P < .001), whereas duration of febrile days of 37.0°C or greater or 37.5°C or greater was not significantly correlated with AHI or ODI. In the multiple regression analyses, forced-entry and stepwise models revealed that the AHI had a significant positive association the duration of febrile days 38.0°C or greater even after adjusting for other variables (P < .001). The severity of sleep apnea was associated with a high incidence of respiratory infections in bedridden elderly adults. A high prevalence of SAS was also observed in bedridden elderly adults residing in a long-term care facility. More than 90% of the patients had an AHI greater than 5 events/hour, and more than 50% had moderate to severe SAS. These percentages were much higher than the reported incidence of SAS in community-dwelling elderly adults.9, 10 These findings support that bedridden elderly adults with sleep apnea are likely to develop lower respiratory tract infections. Early diagnosis and interventions aimed at treating sleep apnea may contribute to the prevention of pneumonia. This work was supported by grants-in-aid for young scientists from the Ministry of Education, Science, Sports and Culture of Japan. Conflict of Interest: No conflicts of interest to disclose. Author Contributions: Dr. Ishii: Had access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the analysis. Ishii and Yamaguchi: Study concept and design, analysis and interpretation of data, drafting the manuscript. Ishii, Osumi, and Nakamura: Acquisition of data. Yamaguchi, Yamamoto, and Ouchi: Editing the manuscript. Sponsor's Role: No sponsor.