Severe brain atrophy in the elderly as a risk factor for lower respiratory tract infection

Rieko Okada,¹ Takashi Okada,² Akira Okada,² Hideyuki Muramoto,³ Masahisa Katsuno,⁴ Gen Sobue,⁴ Nobuyuki Hamajima<sup>1

1</sup>Department of Preventive Medicine, Nagoya University Graduate School of Medicine, ²Okada Medical Clinic, ³Muramoto Clinic, ⁴Department of Neurology, Nagoya University Graduate School of Medicine, Nagoya, Japan

Background: The purpose of this study is to determine whether elderly subjects with severe brain atrophy, which is associated with neurodegeneration and difficulty swallowing (dysphagia), are more susceptible to lower respiratory tract infections (LRTI), including pneumonia.
Methods: The severity of brain atrophy was assessed by computed tomography in 51 nursing home residents aged 60–96 years. The incidence of LRTI, defined by body temperature ≥ 38.0°C, presence of two or more respiratory symptoms, and use of antibiotics, was determined over 4 years. The incidence of LRTI was compared according to the severity and type of brain atrophy.
Results: The incidence rate ratio of LRTI was significantly higher (odds ratio 4.60, 95% confidence interval 1.18–17.93, fully adjusted P = 0.028) and the time to the first episode of LRTI was significantly shorter (log-rank test, P = 0.019) in subjects with severe brain atrophy in any lobe. Frontal and parietal lobe atrophy was associated with a significantly increased risk of LRTI, while temporal lobe atrophy, ventricular dilatation, and diffuse white matter lesions did not influence the risk of LRTI.
Conclusion: Elderly subjects with severe brain atrophy are more susceptible to LRTI, possibly as a result of neurodegeneration causing dysphagia and silent aspiration. Assessing the severity of brain atrophy might be useful to identify subjects at increased risk of respiratory infections in a prospective manner.

Keywords: brain atrophy, dysphagia, elderly, pneumonia, respiratory infection, white matter lesions