2.2.2 Health function status
(1) Comorbidity: the Charlson comorbidity index (CCI) was used. It consists of 19 items: diabetes mellitus (diabetic complications), congestive heart failure, peripheral artery disease, chronic lung disease, moderate or severe liver disease, hemiplegia, kidney disease, leukaemia, lymphoma, tumour metastasis and AIDS. Each of the items is weighted according to its impact on mortality [18].
(2) Disease severity: the Acute Physiology and Chronic Health Evaluation II (APACHE II) was used. This tool aims to comprehensively assess acute physiology, age and chronic health status. The final score is the sum of the three subscores. The higher it is, the more serious the disease [19].
(3) Cognitive function: The short portable mental status questionnaire (SPMSQ) was used [20, 21]. It concerns orientation, personal history, recent memory and computational power. The cognitive function level of the subject was assessed according to educational background (primary school, junior high school, senior high school and above). Furthermore, those clinically diagnosed with Alzheimer's disease ,or those with severe cognitive impairment written in the electronic medical record and unable to be evaluated by the scale were directly judged as having severe cognitive dysfunction.
(4) Ability of daily living: The Barthel Index (BI) was used [22], which is comprised of 10 items with a total score range of 0-100. It is classified into five levels: self-care (100 points), mild disorder (75–95 points), moderate disorder (50–70 points), severe disorder (25–45 points), and extremely severe disorder (0–20 points).
(5) Swallowing function evaluation: the Kubota water swallow test was used [23]. The time required for patients to swallow 30 ml water taken by mouth was recorded. The test was carried out once to record the shortest time and the occurrence of choking and coughing. This test has been widely used nationwide with good reliability and validity. If the result of this test is positive, the patient would undergo the standardized swallowing assessment. Patients who need gastric tube feeding were directly judged as dysphagia.
Standardized swallowing assessment (SSA): the SSA includes three parts: clinical examination, a 5 ml water swallow test 3 times, and a 60 ml water swallow test [24]. Difficulty swallowing is observed during the test. The final score ranges from 18 to 46. The higher the score is, the more pronounced the dysphagia is. Patients whose score was ≥ 19 were considered to have dysphagia.
In this study, people with a score < 22 were tested again at an interval of 20 minutes. If the two scores were identically 18 or identically ≥ 19, no more tests were implemented. If one score was > 18 and another score was 18, a third test was implemented after another 20 minutes. If the third score was > 18, the patient was considered to have dysphagia.
The final determination of dysphagia was based on the positive results of both the Kubota water swallow test and the SSA. Moreover, dysphagia was directly determined if the patient was ordered to use nasogastric tubes by doctors.
2.2.3 Prognosis
Complications (malnutrition and aspiration pneumonia), readmission, and death were investigated.
2.2.3.1 Malnutrition
The Mini Nutritional Assessment Short Form (MNA-SF) was used to assess the nutritional status of the subjects [25]. The simplified MNA-SF scale includes six indexes: decreased food intake (3 months), weight loss (3 months), occurrence of stress or acute disease (3 months), mobility, neuropsychiatric disease, and body mass index (if the body mass index cannot be measured, the calf circumference is measured instead). The total score ranges from 0 to 14. A total score of < 8 indicates malnutrition.
2.2.3.2 Aspiration pneumonia
Aspiration pneumonia was judged according to the doctor's clinical diagnosis. If the type of pneumonia was not indicated in the medical record, it was judged by 2 deputy chief doctors with expertise in elderly respiration. The following indicators were necessary for diagnosis: history of aspiration, chest X-ray showing pulmonary fibrosis (or increased infiltration) or moist rales on chest auscultation, and at least two of three symptoms (① fever over 38 ℃, ② number of white blood cells in the blood > 10000/mm3, ③ decreased content of oxygen in the blood [10]).
2.2.3.3 Death
The mortality of all of the patients by the end of the 6-month follow-up was investigated.
2.2.3.4 Readmission
The readmission rate (into hospitals, rehabilitation institutions or therapeutic nursing homes) of the live patients over the 6-month follow-up was investigated.