Corresponding author:
Naoyuki Miyashita, MD, PhD,
First Department of Internal Medicine,
Division of Respiratory Medicine, Infectious Disease and Allergology,
Kansai Medical University,
2-3-1 Shin-machi, Hirakata, Osaka 573-1191, Japan.
Telephone: +81-72-804-0101; Fax: +81-72-804-2504
Email:miyashin@hirakata.kmu.ac.jp
Keywords: activity of daily living, functional outcome, Omicron
variant, SARS-CoV-2, COVID-19
Dear Editor
In a previous study, we demonstrated that advanced age was a risk factor
for functional decline at 1 year in hospitalized elderly patients with
pneumonia due to SARS-CoV-2 ancestral strain and Alpha variant [1].
The Delta variant of SARS-CoV-2 is being replaced by the Omicron
variant. In a hamster model, the Omicron variant showed decreased lung
infectivity and lower pathogenicity than Delta and ancestral SARS-CoV-2
[2]. Global case fatalities ranged from 1.7 to 39.0% in February to
March of 2020 when the ancestral variant was predominant; however, they
fell to below 0.3% in July to August 2022 when Omicron was predominant
in Japan [3]. In this period, the pattern of pneumonia changed from
primarily viral pneumonia to pneumonia mixed with bacteria, including
aspiration pneumonia. Bacterial co-infection and secondary bacterial
infection in patients with COVID-19 was low until the Delta variant
[4-6].
The Japan Respiratory Society (JRS) pneumonia guidelines emphasize the
importance of pneumonia prevention rather than antibiotic therapy to
avoid deterioration of physical function in the elderly [7].
Functional decline after hospitalization due to pneumonia often induces
aspiration pneumonia especially in those aged ≥ 80 years old after acute
febrile illness such as a viral infection [7]. The objective of this
study was to clarify the functional outcomes at 1 year after hospital
discharge in elderly patients (≥ 80 years old) hospitalized for
pneumonia due to SARS-CoV-2 Omicron variant. We compared the functional
outcomes between primary viral pneumonia and pneumonia mixed with
bacteria groups.
The present study was conducted at five institutions between December
2021 and August 2022. Activities of daily living (ADL) was used to
calculate the Barthel Index, which consisted of the following 10
indices: feeding; bathing; grooming; dressing; bowels; bladder; toilet
use; transfers; morbidity; and stairs [8]. In the present study, we
calculated the difference in ADL scores between baseline (1 week before
admission), at hospital discharge, and 1 year after discharge from our
hospitals. The difference was categorized into two groups: declined (≥
1) and not declined (0). Of the pneumonia cases, we excluded bedridden
cases because these patients were not able to change their ADL score
between before and after admission to hospital.
During the study period, 891 elderly patients with pneumonia due to
SARS-CoV-2 Omicron variant were recognized. Of these, we enrolled 303
patients with primary viral pneumonia and 326 patients with pneumonia
mixed with bacteria that we could follow-up for 1 year. Bacterial
co-infection and secondary bacterial pneumonia were defined using
bacteria detected by sputum culture or urinary antigen tests, and
bacterial pneumonia prediction score using the JRS pneumonia guidelines
(0 or 1 point) [9].
Functional decline rates at the time of hospital discharge were higher
in the primary viral pneumonia group than the pneumonia mixed with
bacteria group (52.3% vs. 40.3%, p = 0.0024) (Table 1). Of 171
patients in the pneumonia mixed with bacteria group who had a decline in
physical function at the time of hospital discharge, 139 patients
(81.3%) still showed functional decline at 1 year later. On the other
hand, in the primary viral pneumonia group, 20.5% of patients had
functional decline at 1 year after hospital discharge, which is
significantly lower (p < 0.0001). Among the BA.1, BA.2,
and BA.5 Omicron subvariant groups, functional decline rates at the time
of hospital discharge and at 1 year after hospital discharge were
similar in both groups.
In our previous study, we
followed up ≥ 80 years old elderly patients with pneumonia due to
SARS-CoV-2 ancestral strain and Alpha variant and demonstrated that
42.5% showed a decline in function 1 year after hospital discharge
compared to their baseline ADL function [1]. In the present study,
functional decline rates at 1 year after hospital discharge were
significantly lower in the primary Omicron variant pneumonia group
(20.5%) than the primary ancestral strain and Alpha variant pneumonia
group (p < 0.0001). In contrast, functional decline
rates at 1 year after hospital discharge were similar between the groups
(p > 0.9999).
With the decrease in pathogenicity of Omicron variant, functional
decline rates at 1 year after hospital discharge were significantly
decreased in the primary Omicron variant pneumonia group compared to
primary ancestral strain and Alpha variant pneumonia group. On the other
hand, a high incidence of functional decline was observed in elderly
Omicron pneumonia with bacterial co-infection.
Our findings suggest that physicians should recommend the use of
anti-SARS-CoV-2 drugs and SARS-CoV-2 vaccination when COVID-19 is found
in patients who are ≥ 80 years old even though the predominant strain is
the Omicron variant.