Swallowing-related cough and health status of old adults: Results from a nationwide cross-sectional study

To the Editor: Swallowing-related cough is a common manifestation of oropharyngeal dysphagia, and confirms the risk of aspiration and choking.[1,2] Choking-related death was the common cause of accidental death in old adults. Because of the difficulty of first aid, 80% of choked people died before the emergency team arrived, which stresses the importance of monitor and prevention of swallowing-related cough.[3] Additionally, swallowing disorder intertwines with various aging-related conditions, such as frailty, sarcopenia, and dementia, and is the crossed manifestation of aging-related health decline.[2] Currently, swallowing-related cough was mainly considered as one of the screening criteria of dysphagia and risk indicator of aspiration pneumonia, while the actual screening rates in clinical practice were extremely low.[1,2] Clinical guidelines on aspiration pneumonia and dysphagia, which involve swallowing-related cough, recommend to intensify oral care, test for dysphagia, and initiate swallowing rehabilitation early. But these actions highly depend on formal caregivers and specialists. Considering the circumstances lacking formal caregivers, it would be more pragmatic to find an easy-to-notice risk factor. Comprehensive geriatric assessment (CGA) was the consented solution of multidisciplinary healthcare of old adults. However, the initiation of CGA in the circumstances lacking formal caregiver remains unsettled. In the perspective of health monitor, the advantage of swallowing-related cough is easy-to-notice. It is valuable to investigate the clinical significance of swallowing-related cough on health decline in old adults and determine whether it is a worth-to-use indicator. Besides, it is also essential to explore the related factor of swallowing-related cough, which could guide the prevention and management of swallowing-related cough, minimizing the need for intensified care among high-risk population. Therefore, the present study investigated the prevalence and related factor of swallowing-related cough, and evaluated its association with health decline of old adults. The present study was based on the China Psychosomatic Health Survey Based on the Traditional Chinese Medicine (CPHS-TCM), which is an ongoing nationally representative cross-sectional survey focusing on adults ≥45 years using the design of hospital-based cluster sampling in 16 provinces of Chinese mainland considering the geographical and culture variation [Supplementary Method 1, https://links.lww.com/CM9/C134]. Among 12,766 adults interviewed from January 2021 to August 2022, participants in the absence of data on swallowing-related cough or oropharyngeal factors (n = 550), health status (n = 288), or chronic disease (n = 46) were excluded. Ultimately, 11,882 participants aged ≥45 years with complete data were included [Supplementary Figure 1, https://links.lww.com/CM9/C134]. The CPHS-TCM was approved by the Ethics Committee of Beijing University of Chinese Medicine (No. 2020BZYLL0805). All participants provided written informed consent. Swallowing-related cough was identified if the participants answering “sometimes” or “often” to the question “Do you cough or choke when you eat or drink?”. Oral conditions were identified by graded answers of the following questions: (1) Do you have trouble in chewing due to tooth problem? (No, mild, moderate, severe) (2) Do you feel dry mouth and/or throat? (Rarely, sometimes, frequently) (3) Do you have halitosis? (Rarely, sometimes, frequently) (4) Is your tongue coat thick? Airway conditions were identified by graded answers of the following questions (1) Do you have trouble in breathing affecting your sleep? (<1 time/week, 1–2 times/week, ≥3 times/week) (2) Do your cough or snore affect your sleep? (<1 time/week, 1–2 times/week, ≥3 times/week) (3) How frequently do you have an allergic reaction (to drug, food, smell, pollen, or season change)? (Rarely, 1–2 times/year, ≥3 times/year). Quality of life was evaluated by the Short Form 36 (SF-36) health survey questionnaire. Total, physical, and mental health status were defined by quartiles of SF-36 score, respectively. Physiological reservation was reflected by the status of frailty using the FRAIL scale. Independence of daily life was evaluated by Barthel activities of daily life (ADL) index and instrumental ADL (IADL) scales. General health was assessed by body constitution of Chinese medicine using Constitution in Chinese Medicine Questionnaire (CCMQ),[4] recorded as balanced constitution, 1 type of bias constitution, and ≥2 types of bias constitution [Supplementary Method 2, https://links.lww.com/CM9/C134]. Hypertension, diabetes, dyslipidemia, mental disease, sensory disorder, neurocognitive disorder, respiratory diseases, gastrointestinal diseases, cerebrovascular diseases, cardiovascular disease, urological disease, and musculoskeletal disease were identified by self-reported history, lab tests, and/or standard scales [Supplementary Method 3, https://links.lww.com/CM9/C134]. Comparison of characteristics between participants with or without swallowing-related cough was performed using Student’s t-test and chi-squared test. Prevalence of swallowing-related cough was analyzed. The associations between swallowing-related cough and general health (SF-36 of total, physical health, and mental health, and body constitution) as well as the physical function (frailty, IADL, and ADL) were analyzed using multinomial logistic regression models. The associations between oropharyngeal factors and chronic disease as well as the odds of swallowing-related cough were analyzed using multivariable logistic regression models. Considering the influence of feed by others on swallowing, sub-group analyses were performed in the population having meals independently or not. Sensitivity analyses were performed among population excluding those having well-known contributors of swallowing-related cough including cerebrovascular disease, neurocognitive disorders, mental disease, or respiratory disease [Supplementary Method 4, https://links.lww.com/CM9/C134]. In total, 11,882 adults (69.0 ± 6.8 years) were recruited. Characteristics of participants can be found in Supplementary Table 1, https://links.lww.com/CM9/C134. The overall prevalence of swallowing-related cough was 13.3% (1583/11,882). Compared with the youngest or the healthiest group, adults aged ≥75 years, with the lowest levels of SF-36 scores, frailty, moderate to severe dysfunction of ADL and IADL, and having ≥2 types of bias body constitutions showed 2-fold to 5-fold higher rates of swallowing-related cough [Figure 1A].Figure 1: (A) Prevalence of swallowing-related cough. (B) Association between swallowing-related cough and odds of health deterioration after adjusting for age, sex, smoking, drinking, BMI, multimorbidity, and needing assistance for meals. (C) Association between oropharyngeal factors and the odds of swallowing-related cough after adjusting for age, sex, smoking, drinking, BMI, and multimorbidity. ADL: Activities of daily life; BMI: Body mass index; CI: Confidence interval; Q: Quartile; OR: Odds ratio; Ref.: Reference; RRR: Relative risk ratio; SF-36: Short Form 36.Swallowing-related cough was significantly associated with the higher odds of deterioration of quality of life (scores of SF-36), independence of daily life (Instrumental ADL, Barthel Index of ADL), physiological reservation (frailty), and general health (Constitution of Chinese Medicine) [Figure 1B]. The sub-group analyses on adults having meals independently showed similar results with the overall population [Supplementary Figure 2, https://links.lww.com/CM9/C134]. Tooth problem showed the strongest association with swallowing-related cough, followed by difficult breathing and coughing or snoring influencing sleep, dry mouth or throat, thick tongue coat, halitosis, and frequent allergy [Figure 1C]. The increased risk of dry mouth or throat and thick tongue coat on the swallowing-related cough disappeared among participants having meals independently, while remained among those needing assistance for meals [Supplementary Table 2, https://links.lww.com/CM9/C134]. Adults with mental disease or sensory disorder were with 3-fold odds of swallowing-related cough, followed by cerebrovascular disease, respiratory disease, musculoskeletal disease, hypertension, and dyslipidemia. The risk association between neurocognitive disorder and swallowing-related cough reported by previous studies was found only among those needing assistance for meals, but not in the overall population or among those having meals independently [Supplementary Table 3, https://links.lww.com/CM9/C134]. Sensitivity analyses showed similar results to the main analyses [Supplementary Tables 4 and 5, https://links.lww.com/CM9/C134]. According to the results, swallowing-related cough was capable to signal the deterioration of physical function, mental health, and general health like body constitution of old adults. Considering the importance of swallowing-related cough in oropharyngeal dysphagia, aspiration pneumonia, and choking, it is reasonable to transfer old adults with frequent swallowing-related cough to formal caregiver and specialist to screen dysphagia and aspiration pneumonia, and to initiate CGA and swallowing rehabilitation. The present study provides evidence on the identification of high-risk population and prevention of swallowing-related cough in daily life. In addition to stroke and dementia, which is reported as risk contributor of swallowing disorders in previous studies,[1,2] we found that adults with sensory disorder or mental disease should be identified as the high-risk population of swallowing-related cough and receive specific monitor and intervention, and intervention of tooth problem should be the prior task. In addition to the significance on oral hygiene, traditional Chinese medicine defined persistently thick tongue coat as an indicator of indigestion and over-nutrition, and defined halitosis as the signal of indigestion and stomach disease. Dry mouth/throat is the typical symptom of Sjögren syndrome, but more commonly, it indicates dehydration. Taking together, it suggests the feasibility to moisturize food and modify food quantity in accordance with the feature of mouth and tongue coat, especially for those who need assistance for meals and unable to describe the food necessity properly. For adults having signs of reduced airway patency, treatment of the primary cause should be the basis to prevent swallowing-related cough. As to the limitations of our study, first, it is a cross-sectionally observational study and cannot make causal conclusion. Second, 6 of 12 types of chronic disease were defined by self-reported data, which might generate report-bias. Third, oropharyngeal factors were evaluated by self-reported questions extracted from standard questionnaires, rather than physical tests. In conclusion, swallowing-related cough is a prevalent problem among old adults and could be an indicator of health status. More attention should be paid on oropharyngeal alteration, which intensively associate with the swallowing-related cough. Funding This work was supported by the National Key R&D Program of China (Nos. 2020YFC2003100 and 2020YFC2003103), the Beijing University of Chinese Medicine Basic Research Operating Funds (No. 2023-JYB-JBZD-023), the National Natural Science Foundation of China (Nos. 82100741 and T2341006), the Natural Science Foundation of Beijing (No. L232118), and the High Level Key Discipline of National Administration of Traditional Chinese Medicine-Traditional Chinese Constitutional Medicine (No. zyyzdxk-2023251). Conflicts of interest None.