14 Inhalant Allergies and Asthma in the Geriatric Population
Introduction
Tradition says that older adults are less likely to suffer from allergies, but recent studies show that many elderly people do suffer from allergic diseases and/or asthma.1 Because there is a general lack of awareness that geriatric atopy occurs, it is often excluded from the differential diagnosis in older patients presenting with nasal congestion, postnasal drip, rhinorrhea, cough, wheezing, or shortness of breath.
In the geriatric patient, there are numerous causes other than atopy that may present with nasal congestion or cough. Some of these include vasomotor or gustatory rhinitis, chronic obstructive pulmonary disease (COPD), and bronchitis, all of which are common in the geriatric population. Add to this the multiple comorbidities often present, and the general lack of knowledge that allergies occur in elderly patients, and it is no surprise that clinicians often fail to consider geriatric atopy. Overlooking this important entity deprives the elderly of appropriate treatment, symptom relief, and, ultimately, improvement in quality of life.2
Why Assume Allergies Are Uncommon in the Elderly?
Immunosenescence is defined as aging of the immune system. This affects both the innate and the adaptive immune systems, with a general decrease in immunocompetence. Consequent to this decreased immunocompetence is an increase in chronic and infectious diseases among the elderly.3,4 There is decreased function of B and T cells, with a reduction in diversity among both populations.1 With aging, the response to many vaccines is less robust. For example, administering a flu vaccine in young adults causes a response in 70 to 90% of people, whereas a similar vaccination in older patients results in a response of only 17 to 35%.1,5
The lower vitamin D levels found in many older patients also hinder a vigorous immune response.1 Vitamin D promotes the function of antigen-presenting cells (APCs) and T cells. A lack of vitamin D can hinder the induction of T-regulatory (Treg) cells and the development of tolerance, which is a crucial part of the allergy immunotherapy response.
Collective consideration of these facts may help explain why many clinicians assume allergy and asthma are rare in the elderly.
Incidence of Allergies in the Elderly
Allergies affect ~ 20% of the population worldwide. The general assumption is that this is proportionally higher in younger patients, with a slow steady decline as patients age.
Several studies have shown an age-related decrease in total and specific immunoglobulin E (IgE).1,6 Skin prick testing (SPT) was positive in 28.4% of patients referred to an Italian allergy unit, but this was a selected population of elderly people who had allergy symptoms.7 Karablut et al looked at geriatric patients with symptoms of allergic rhinosinusitis (AR) compared with a young control group. The rate of SPT positivity was ~ 50% in the older group and ~ 75% in the younger control group.8
There are, however, also data suggesting that allergies do not decrease substantially with aging. DiLorenzo et al found no changes in serum IgE or T-helper cell type 2 (Th2) cytokines with aging.9 A survey of 109 geriatric nursing home patients (mean age 77) tested by interview, SPT, and serum total and specific IgE (sIgE) reported a positive SPT and/or sIgE in ~ 40% of those tested.10 A large Swiss study using in vitro testing showed the incidence of atopy in men under versus over 60 to be ~ 36% versus 26%, and in women 31% versus 18%.11 Another researcher noted that severe allergies are worse as the nasal mucociliary clearance time lengthens, which typically happens with aging.12
We can accurately conclude that allergies do exist among those over the age of 65 in numbers that are clinically meaningful. If there is, in fact, a lower incidence of inhalant allergies in the elderly compared with the young, this may mean that allergies occur in a greater percentage of the young population and decrease in that same population over time. When today’s 70-year-old was age 10, however, the overall incidence of allergies was substantially lower than it is in today’s 10-year-olds. Perhaps today’s lowered measured incidence of allergy in the older patient represents the constant rate of allergy in an aging cohort, rather than a diminution of allergy over that person’s lifetime. Only future longitudinal studies will distinguish between these two possibilities.
Incidence of Asthma
The overall incidence of asthma in individuals over the age of 65 is often quoted as being 6 to 10%.1 One study in Texas of the elderly reported a 6.3% incidence of asthma, with another 9% having “probable asthma.”13 A Korean study of over 2,000 people noted an incidence of asthma (based on a questionnaire and methacholine challenge) ranging from 2% in those under 40, to 12.7% in those 65 or older.14 In the aforementioned large Swiss study, a little over 8% of those under 60 had asthma, compared with ~ 7% for those over 60.11
Older patients are more likely to have wheezing, shortness of breath (SOB), and cough than younger age groups. These presenting symptoms may be presumed to indicate conditions known to be more common in the older age group (COPD, bronchitis, congestive heart failure) without investigating the possibility of a reversible component. This can lead to major clinical difficulties. It is noteworthy that asthma deaths in younger patients are decreasing, whereas asthma mortality is increasing in older patients. Part of this problem may stem from an inaccurate diagnosis in the elderly to begin with. Hospens et al noted that, among geriatric patients with respiratory problems, the presence of airway hyperreactivity was associated with a more rapid decrease in pulmonary function and significantly worse exacerbations.15 Spirometry is accurate in the elderly11 and can be used in the office setting to reliably distinguish reversible from irreversible obstructive pulmonary disease. This useful tool helps prevent the misdiagnosis and consequent inappropriate treatment of a respiratory problem such as COPD when it is actually asthma.
A large significant percentage of asthma in the elderly has allergic triggers.16 King et al described significantly more inhalant allergies in elderly patients with asthma compared with those without asthma (odds ratio 13).16 In Baltimore, Huss et al noted that, of 80 asthmatic patients over age 65, 75% had at least one positive SPT.17 Ariano et al documented that, among patients with asthma, 72% had at least one positive SPT.18Jackola et al demonstrated no age-related difference in the incidence of ragweed allergy among asthma patients.19 Parameswaran et al reported that a history of atopy was a very strong predictor of asthma among the elderly.20
How Are Allergy and Asthma Best Diagnosed in the Geriatric Population?
As with most things in medicine, diagnosis begins with a thorough history and physical examination. The history may contain clues such as seasonality (worse symptoms in spring suggests tree pollen allergies), location (symptoms occurring in a musty basement may be due to mold), or proximity (visiting a friend who has a cat always results in wheezing). Daily symptom scores and records of medication use can be used to estimate the severity of allergic disease. On physical examination, there may be “allergic shiners” (dark circles under the eyes due to venous congestion) or an allergic crease on the nose (horizontal wrinkle just above the lower lateral cartilages due to habitual rubbing of the hand upward under the nose), or even frank wheezing. Speculum examination of the nose or endoscopy often reveals edematous mucosa, which is typically pale or faintly bluish in color.
Diagnosis is confirmed with allergy testing, in vitro testing (measuring levels of antigen-specific IgE in the serum), or skin testing (applying small amounts of potential allergen into the skin looking for stimulation of histamine release). Skin testing can be either epicutaneous (SPT) or intradermal dilutional testing (IDT).
SPT is performed with concentrated antigen, usually 1:20 weight to volume (w:v) or equivalent. Because the IDT inserts antigen deeper into the skin where there are more reactive cells, more dilute solutions of antigen are used. Classic IDT uses serial injections of each antigen, ranging from very dilute (dilution no. 6, or 1:312,550) to more concentrated (dilution no. 2, or 1:500). Positive histamine and negative saline controls are used in both types of testing, with a negative glycerine control sometimes also used. There are also methods of combining these two techniques, as in modified quantitative testing.21
Other testing used mainly in research includes nasal provocation (insufflation of allergen into the nose while measuring the nasal airway before and after using acoustic rhinometry) and conjunctival challenge (applying allergen directly to the conjunctiva).
A final confounder in the diagnosis of inhalant allergies is local allergic rhinitis (LAR).22,23 This is a condition where allergic symptoms are present, perhaps even a response to antihistamines, but skin and blood testing are negative. In some of these patients, sIgE is present in nasal secretions, brush biopsy, washings, or tissue biopsy. Rondón et al reported the presence of local nasal sIgE in ~ 40% of patients who had previously been assigned a nonallergic diagnosis.24,25
How Does Aging Affect Allergy Testing?
Although the mechanics of in vitro testing are unchanged by age, this investigation is widely regarded as less sensitive than skin testing. Skin changes with aging as skin histamine response declines, with atrophy of the epidermis and dermis and a decrease in collagen and cellularity. Solar damage can cause false-negative skin test results.26–28 Some suggest that these age-related skin changes generally increase the chance of false-negative testing, and even suggest that we may need different criteria for the interpretation of skin testing in geriatric patients.
One possible alternative is to follow negative SPT with IDT in the elderly patient. An older study by Nelson et al addresses the question of whether negative SPT in older patients with a positive allergic history should be followed by IDT.29 In this report, patients were divided into four groups based on history, SPT results, and IDT results. Group 1 had a positive history, negative SPT, and positive IDT. Group 2 had a positive history and positive SPT. Group 3 had a positive history and negative SPT and IDT. Group 4 had a negative allergic history and negative SPT. When they defined AR as having a positive response to nasal challenge and having current symptoms, the incidence of AR was 46% in group 2 and zero in the other three groups. In other words, in this study, finding a positive IDT after negative SPT did not identify clinical allergic rhinitis.
Who Should Be Tested and How?
Any patient, old or young, with symptomatic asthma, rhinitis, or conjunctivitis should be considered for allergy testing. In addition, patients with sinus disease severe enough to warrant endoscopic sinus surgery (ESS) should be allergy tested if there has been no such testing within the past 5 years. Allergy skin testing is more sensitive and is therefore preferred to in vitro testing when practical and safe. When performing in vitro allergy testing, it is good practice to also obtain a measurement of total serum IgE. In vitro testing is reserved for the specific situations listed in Table 14.1.
If in vitro testing is negative and total IgE is elevated, further in vitro testing may be illuminating because clinically significant atopy is likely. If in vitro testing is negative and total IgE is in the normal range, testing can either stop at that point or continue to skin testing, depending on the degree to which the potentially allergic symptoms affect the patient.
Trouble-Shooting Allergy Skin Testing
Antihistaminic medications must be stopped ~ 10 days before allergy skin testing to permit stimulation of an adequate histamine response.
For some patients who have difficulty discontinuing antihistamines, a brief oral steroid burst when the antihistamines are withdrawn may help control severe symptoms before testing. Oral steroids do not interfere with allergy skin testing. Monoamine oxidase inhibitors and tricyclic antidepressants should be stopped ~ 5 days prior to testing.
Beta-blockers are withheld for 2 to 3 days prior to testing, if permitted by the prescribing physician. For a patient on a cardioselective β-blocker that cannot be stopped for 2 to 3 days to permit skin testing, slow, cautious skin testing is generally safe. Because the risk of a systemic reaction is related to the total allergic load applied, the tests are applied slowly. If multiple large reactions occur, the remainder of the testing is spread out over one or more additional days. Multiple recent articles suggest that the risk associated with a cardioselective β-blocker is lower than that with one like propranolol, and that the overall risk of a β-blocker and allergy skin testing may have been overestimated.30
Table 14.1 Indications for in vitro allergy testing rather than skin testing
Comorbidities that put the patient at high risk for cardiovascular instability—could increase the morbidity/mortality if a systemic reaction occurred |
Patient taking a β-blocker, including β-blocker eyedrops—if epinephrine is required for a systemic reaction, the unopposed α-effect could be challenging to manage |
Poorly controlled asthma—puts the patient at higher risk for developing a systemic reaction |
Antihistamines cannot be stopped (severe urticaria, etc.)—suppresses skin wheal responses |
Dermagraphism or other widespread dermatitis—makes accurate interpretation of wheal size difficult |
Negative skin testing with high total serum immunoglobulin E (IgE)—suggests that atopy exists |
