ALLERGIC DISEASE IN AN AGING POPULATION

Abstract

As we approach the twenty-first century the demographics of our patient population are changing. Life expectancy has increased by 4 to 5 years over the previous two decades. As a result, over the previous decade the population over the age of 65 has been the fastest growing group. 15 In fact, those more than 85 years of age grew at a rate of 41% compared with the overall US growth rate of 11%. In 1994 those individuals more than 65 years of age made up 12.6% of the total population of the United States and numbered more than 30 million. Furthermore, as the baby boomers enter their fifth decade and continue to age in the early twenty-first century, they will add to this growing number. It is estimated that between 2010 and 2030 the population more than 65 years of age will increase by 75%. 8,15,22 As the population ages clinicians must be prepared to meet the elderly's health care needs. To meet these patients' needs their specific and unique circumstances must be considered. Many of the unique health care needs of the elderly are considered in this article as well as in subsequent articles in this issue. Although atopic diseases most commonly present in the first three decades of life, many of these diseases may persist. Additionally, because many common illnesses masquerade as atopic disease, the differential diagnosis of suspected allergic diseases becomes more expanded in an aging population. Perhaps the most important allergic disease to consider in the elderly is asthma. Although not all asthmatic patients have definable allergic triggers to their asthma, many if not most do. Frequently the allergic nature of asthma in the elderly is ignored. Asthma is a chronic inflammatory disease that can affect individuals of any age. There appears to be a bimodal distribution of asthma prevalence in the elderly. 2,3,4,5,6 Whereas the prevalence of asthma drops from 10% to 5% from childhood to early adulthood, it rises to 7% to 9% in the elderly. In fact, approximately one third of adults with a history of childhood asthma remission will have a recurrence after 45 years of age. The diagnostic challenge of new-onset asthma in the elderly may be a distinct disorder and is discussed in a subsequent article. It has become increasingly clear that allergen exposure early in life can be associated with sensitization to inhalant allergens. Although chronic inflammation triggered by environmental allergens appears to play a major pathogenic role in childhood asthma, these exposures have a less important role in the elderly. 3 Although skin testing to inhalant allergens may remain positive, their significance should be cautiously interpreted. One must keep in mind that many elderly asthmatics may have chronic irreversible obstructive changes that exceed the predicted normal declines in pulmonary function that occur with age. Coexistent chronic obstructive pulmonary disease and cigarette smoking may be confounding factors in many patients. Furthermore, there appears to be an age-related decline in β receptor and steroid receptor activity, which can alter the clinical expression of asthma in the elderly. Response to β 2 -agonist bronchodilator appears to be lessened in the elderly and may further impair the ability to establish a definitive diagnosis. 7 Performing pulmonary function studies with and without bronchodilators and possible use of methacholine challenge can distinguish underlying bronchial hyperresponsiveness from normal aging changes or fixed obstruction as a result of chronic asthma. 8 Despite the ready availability of diagnostic testing, it has been suggested that asthma is in fact underdiagnosed in the elderly. Clinicians and patients who regard allergy as a condition of childhood and young adulthood may miss important environmental triggers to respiratory disease while focusing on pharmacologic symptomatic treatment. Coexisting illnesses or treatments such as congestive heart failure, gastroesophageal reflux, and use of angiotensin converting enzyme inhibitors frequently mask the characteristic presentation of asthma in the elderly. These concepts and individual conditions are discussed in detail in this issue. Allergic rhinitis is the most common allergic disease, affecting approximately 17% of the general population. Although allergic rhinitis has its peak prevalence during young adulthood, rhinitis remains an important health problem in the elderly. As the aging process ensues, normal physiologic changes may result in rhinitic symptoms, which may further aggravate underlying allergic disease. 22 Paranasal sinus disease may be a primary condition or occur as a secondary complication of allergic rhinitis. Changes in the mucosal, cellular, and humoral immune system that occur in aging may predispose the elderly to chronic indolent infections. The differential diagnosis of allergic nasal disease is further highlighted in Slavin's article on sinusitis in the elderly.