In developed countries, the prevalence of bronchial asthma in the elderly (referred to as geriatric asthma) is as high as 6%, and there are still many undiagnosed asthma in this elderly population [1, 2]. There is a female predominance in the 64-75 age group, with no significant gender differences above 75 years of age. Two-thirds of deaths due to asthma are composed of patients over 65 years of age, which may be related to risk factors such as advanced age, psychiatric factors (depression/anxiety), smoking, and underlying cardiovascular, pulmonary, and renal diseases. Health care resources for outpatient, inpatient, health care, and co-morbidity management are significantly higher in elderly asthma than in young asthma [3, 4]. Therefore, geriatric asthma has become a growing concern worldwide [5, 6]. I. Definition of asthma in the elderly The definition of asthma includes pathophysiological and clinical features, and the clinical symptoms mainly include nocturnal paroxysmal shortness of breath with coughing and wheezing, airway obstruction in the expiratory phase, and pathological features manifesting as airway inflammation and airway remodeling. Old age refers to adults older than 64 years of age, of which those aged 64-75 years are called early old age and those aged 75 years or older are called late old age. Chronological, physiological and sociocultural staging is useful for health-care management of asthma in the elderly. In most countries, the retirement age is 60 or 64 years, which better defines the age group served by health care management agencies, while the late old age is defined at 75 years based on changes in social mobility, reduced social activity, and preference for residential settings, which contribute to the priority of health care service delivery. In addition, geriatric asthma can be classified as longstanding asthma (LSA) or early-onset asthma (EOA) and late-onset asthma (LOA) (age at first visit >65 years). 40-50% of geriatric asthma is first diagnosed at around 40 years of age [7, 8]. II. Difficulties in the diagnosis of asthma in the elderly Diagnosis of asthma requires clinical symptoms and assessment of objective variable airflow obstruction, but almost 50% of elderly asthma is underdiagnosed and undertreated [2]. The decrease in FEV1 in asthma patients leads to a decrease in FVC due to an increase in functional residual air volume, while decreased thoracic elasticity and decreased respiratory muscle function both lead to a decrease in lung function and an increase in residual air volume, and this age-related decrease in respiratory function is difficult to distinguish from the effects of disease. Decreased cognitive ability, poor cooperation, and reduced physical strength in older adults make it difficult for them to complete pulmonary function tests, and even if they do, this increases respiratory fatigue in older adults, making the diagnosis of asthma in the elderly difficult. Respiratory symptoms such as dyspnea, wheezing, coughing and nocturnal symptoms all suggest the possibility of asthma. In fact, these symptoms are quite common in older adults >75 years of age, for example, wheezing or whistling sounds can be heard on chest auscultation in about 14% of the elderly population [9] and about 2/3 of the elderly complain of dyspnea [11]. A significant number of elderly patients, consider symptoms such as wheezing and dyspnea as signs of aging or as other diseases and underestimate the severity of symptoms. Symptoms of asthma in the elderly are easily confused with other diseases (COPD, congestive heart failure, pulmonary embolism, GERD, acute bronchitis, bronchiectasis, tumors, etc.), so this requires a systematic and comprehensive consultation. Asthma in the elderly often coexists with other diseases, making it difficult to determine the specificity of asthma-like symptoms, especially in late old age when the non-specificity of asthma-like symptoms becomes more pronounced, further increasing the difficulty of asthma diagnosis. A more typical co-morbidity, the asthma/COPD overlap syndrome [12, 13], is very common in clinical practice, although there is no uniform definition of this syndrome (Table 1). Asthma often has its first onset in young adults, with atopic, eosinophilic infiltration and reversible airway obstruction. In contrast, COPD is of middle-age onset, associated with smoking, neutrophil infiltration, and incompletely reversible airway obstruction. The characteristics of elderly asthma are very similar to COPD in that symptoms may appear in midlife, some airways are reversible, and neutrophil-infiltrating inflammation is present. The ease of treatment failure in elderly asthma is not only due to the overlap of asthma and COPD symptoms, which makes disease identification more difficult, but also because this group of patients is often excluded from clinical trials, resulting in non-coverage of diagnostic and treatment guidelines and leaving clinicians with little knowledge of the treatment of elderly asthma patients with a history of smoking combined with COPD. In the elderly population, 43% of patients hospitalized with a first diagnosis of COPD were diagnosed with asthma 3 years later, while 48% of patients with a first diagnosis of asthma were diagnosed with COPD 3 years later.Price et al. established a clinical symptom-based questionnaire in an attempt to separate COPD from elderly asthmatic patients, but the sensitivity and specificity of this diagnostic tool for clinical application were only 78% and 75%, respectively [ 13]. Other factors such as self-limitation of activities, social isolation, depression, self-denial and misunderstanding of rare late-onset asthma can also lead to delayed or misdiagnosis of asthma. For example, most older adults are reluctant to admit symptoms due to fear of illness and death, and under-reporting of symptoms can affect the diagnosis and treatment of asthma. In addition, the sedentary lifestyle of older patients leads to decreased sensitivity to post-exertional tightness [14] and incomplete response to bronchodilators, which can lead to asthma-like clinical symptoms in older adults without asthma. The specificity of asthma diagnosis in young people can be as high as 99% by asking family history, allergy history, clinical symptoms, asthma history, and bronchial excitation test, but routine airway hyperresponsiveness test is not ideal for diagnosing asthma in the elderly, and its specificity is only about 50%. The application of objective tests for the diagnosis of asthma in the elderly is not commonly used in primary care settings. Instead, patients with asthma-like symptoms are often given inhalation therapy and asked if the inhalation therapy reduces asthma-like symptoms during the follow-up period. This empirical approach is effective in most cases in young people with mild asthma, but in the elderly population it is likely to be misdiagnosed, ineffective or over-treated, and to increase the risk of adverse drug reactions for the patient. Wheezing, shortness of breath and cough are common symptoms that require attention in older adults. Because all wheezing symptoms do not necessarily stem from asthma, objective examination is particularly important in older patients with atypical symptoms. With increasing age, older adults are less able to perceive dyspnea after exertion, and in those with chronic untreated severe airway obstruction due to asthma, dyspnea is avoided by reducing activity, and older patients deny the reduction in activity. Some barriers to performing pulmonary function tests do exist in the elderly population, mainly related to physical and cognitive impairments in older adults, but the fact is that 80-90% of older adults can successfully complete pulmonary function tests with the guidance of a skilled respiratory technician and only about 15% have difficulty completing them correctly [15, 16]. Maximum respiratory flow is difficult to achieve in elderly patients, and failure to achieve maximum respiratory flow can lead to misdiagnosis, and a successful pulmonary function test takes 20-30 minutes longer in the elderly than in young adults [17]. Five to eight measurements are usually required to obtain reliable FVC data [17]. If the obstruction is severe or if the obstruction is not fully reversible, additional pulmonary function test data, such as spirometry and CO diffusion capacity can be used to identify concomitant lung disease. The definition of the lower reference limit of normal pulmonary function in the elderly is also difficult, so more studies are needed in this population to quantify the risk associated with various criteria for airway obstruction screening. When abnormal airway obstruction is found on pulmonary function tests, a bronchodilator test is performed to confirm the diagnosis of asthma; normal pulmonary function does not exclude asthma, and a bronchial provocation test is then required to confirm the diagnosis. If incomplete reversible airway obstruction coexists with variable airflow obstruction with respiratory symptoms, it is more likely to be seen in the asthma/COPD overlap syndrome. Studies have shown that so-called “healthy” older adults have actually undergone physiological changes in airflow obstruction [18]. The GOLD recommended fixed cut-off value of FEV1/FVC <70%< span=""> would overestimate or misestimate airway obstruction in the elderly population [19]. The ERS guidelines for interpretation of lung function recommend that FEV1/FVC should be used to diagnose airway obstruction considering that the lower limit of its normal range should be based on a 95% confidence interval and be corrected for age, sex, height, and race. The use of inappropriate equations may lead to misclassification, and most of the reference equations currently used for the elderly population originate from the non-elderly population [18]. Dynamic monitoring of PEF is beneficial in the diagnosis and follow-up of young asthmatic patients, but cannot be accurately measured in some elderly patients with poor cooperation and muscle weakness. Prospective studies have not confirmed the benefit of PEF monitoring in symptomatic moderate and severe elderly asthma in comprehensive asthma treatment regimens. Sensitivity response to short-acting beta agonists is the second main feature of asthma and is known as reversible airway obstruction. The bronchodilatory effect of inhaled β agonists in the elderly is reduced due to the decrease in the number of β-adrenoceptors in bronchial smooth muscle that accompanies increasing age [20] [21], but does not affect the effect of acetylcholine. The bronchial excitation test with acetylcholine is a safe and valid method, with negative results that exclude asthma and positive results that require interpretation and the evaluation of pre-test probabilities [22]. In contrast, some studies suggest that bronchial sensitivity is increased in the elderly population and that age may be an independent factor influencing airway sensitivity [23]. There is a relationship between the degree of bronchial hyperresponsiveness and pre-excitation lung function, whereby a lower FEV1 is associated with better bronchial hyperresponsiveness. Other factors in the elderly population may also increase airway reactivity, such as atopy or smoking. Recent findings that a variety of inflammatory cells, including polymorphonuclear cells, monocytes, and eosinophils, synthesize NO suggest that NO is an important inflammatory molecule in the expiratory air. The effect of age on exhaled NO is poorly understood, and it appears that NO production and vascular response to NO are low in the elderly population. Exhaled gas NO levels are elevated in infected and inflamed airways, especially in eosinophilic inflammation, and exhaled gas NO levels are elevated in atopic subjects during the allergy season, and inhaled hormones rapidly suppress exhaled gas NO, which may be associated with airway inflammation that suppresses eosinophil infiltration. Studies have shown that monitoring exhaled NO provides better control of asthma symptom exacerbations and hormone doses than guideline- or symptom-based therapy. Exhaled breath NO (FeNO) is more appropriate for elderly asthma as a noninvasive airway inflammation monitoring method, and the new ATS consensus opinion on FeNO recommends FeNO levels for predicting acute exacerbations of asthma and monitoring the control of eosinophil phenotype asthma [24, 25]. IV. Diagnosis and differential diagnosis of asthma in the elderly The clinical symptoms of asthma in the elderly are similar to those of asthma in young adults [26], and these clinical symptoms include paroxysmal wheezing, shortness of breath, and chest tightness that worsen at night or after activity. Most first asthma in >65 years of age is complicated or secondary to upper respiratory tract infection [27], and asthma in the elderly is easily triggered by environmental factors such as cold air, allergens, irritants (smoke), strong odors (perfume), and also by certain medications such as aspirin, NSAIDs, ACEIs, and β-blockers. The use of these drugs is very common in the elderly population and requires clinicians to pay attention to the overall medication use in elderly patients. There are several reasons for the current misdiagnosis and underdiagnosis of asthma in the elderly: (1) in primary care, most patients have their first asthma episode in children and adolescents, which predisposes some community or general practitioners to misinterpret asthma as a childhood disease; (2) asthma symptoms are easily confused with other diseases in elderly patients, so they need to be differentiated from heart failure, pulmonary embolism, emphysema, COPD, GERD, and bronchial tumors. In addition, concomitant co-morbidities and psychosocial aspects can have a serious impact on the diagnosis of asthma in the elderly. It is very difficult to differentiate asthma from COPD in the elderly, and even more difficult to differentiate LOA from COPD. The lung health study showed that acetylcholine-induced airway hyperresponsiveness can be seen in patients with mild to moderate COPD (63% men, 87% women), 85% of whom have smoking-related COPD. morning wheezing is an important feature of congestive heart failure and is easily confused with asthma; heartburn and acid reflux, typical symptoms of gastroesophageal reflux, are not common in the elderly population. Gastroesophageal reflux (GERD) is diagnosed by monitoring esophageal pH, and clinical symptoms manifest as chronic cough and wheezing in 57% of cases [28], but GERD can worsen asthma control. Shortness of breath is a common symptom in the elderly, commonly associated with cardiopulmonary disease, usually following exertion, whereas shortness of breath at rest is not a typical cardiopulmonary disease symptom, such as COPD or primary lung disease, removed during disease progression, and if present, asthma should be suspected first. Paroxysmal nocturnal shortness of breath is a typical feature of congestive heart failure, but it also occurs in some elderly patients with asthma, and many elderly patients avoid shortness of breath by limiting their activities. Decreased perception of airway smooth muscle contractions and denial of symptoms due to fear of illness are reasons for delayed diagnosis in older patients. Activity restriction, social isolation and depression all contribute to delayed diagnosis of asthma in the elderly. Co-morbidity between asthma and COPD is more frequent in the elderly, and studies have shown that long-term asthma leads to airway reconstruction and partial airway obstruction in about 16% of patients with asthma who eventually develop COPD to varying degrees over 20-30 years [29, 30]. History taking and physical examination should also include the upper airway, with special attention to exclude sinusitis and nasal polyps, and questioning should include adverse reactions to other medications, such as aspirin, α-blockers, and angiotensinase inhibitors. The length of asthma should be taken into account in the questioning of medical history, and if there are long-term asthma symptoms, attention should be paid to allergic factors, including occupational exposure and long-term smoking. Patients with a history of past occupational exposure generally have COPD in combination, and in addition, the amount of annual active or passive smoking should be considered. V. OUTLOOK The elderly are a special population in clinical practice. Elderly patients with asthma differ greatly in asthma severity, pathogenesis, environmental irritants, and their respective different lung diseases, and different underlying diseases such as coronary artery disease, hypertension, diabetes mellitus, and Alzheimer’s disease cause great irreversibility in elderly asthma, making the diagnosis and treatment difficult. In future studies, more adequate evidence is needed to support age-related changes in lifestyle, pathophysiology, etc., to define the different clinical phenotypes of geriatric asthma, and to evaluate age-specific health management systems. Comprehensive assessment of geriatric respiratory disease includes management skills, risk factors, and co-morbid treatment. To improve the understanding of geriatric asthma by integrating multiple factors, randomized controlled trials are needed to explore geriatric asthma management guidelines and clinical outcomes.