A recent article published in Immunity & Ageing reviews the various mechanisms involved in allergic diseases in the elderly.
Our immune system plays an important role in protecting us against foreign substances and pathogens. Throughout our lives, our immune cells can become primed to react to unwanted entities, but an over-reaction by the immune system to benign substances is what we consider allergic reactions. One common type of allergic reaction is called immediate hypersensitivity, which include anaphylaxis, asthma, and eczema. These reactions affect around 25% of the population in industrialized nations and a host of factors play into this complex disease: climate, diet, pollution, and compositions of gut bacteria.
Hypersensitivity in the Elderly Population
Most of the research into immediate hypersensitivity, however, has focused on younger populations. As life expectancy increases and the elderly make up a larger part of the population, especially in industrialized nations, it is an increasingly important condition to study in the aged. A group from Italy summarizes the current literature on immunological and non-immunological mechanisms behind allergic diseases in elderly patients in a review article recently published in Immunity & Ageing.
As we age, many aspects of our immune system decline, leading to impaired function. There are many characteristics of an aging immune system, most notably an imbalance in immune cell subtypes and decreased new T cell generation. T cells are an important and prominent type of immune cell involved in cell-mediated immunity. Almost all types of immune cells have alterations and impaired function due to age. In particular, the accumulation of these changes establishes a state of chronic inflammation and heightened allergic immune responses. One noticeable consequence of reduced immune cell function is the greatly hampered efficacy of vaccinations. For example, the influenza vaccine protects significantly fewer in older populations.
Allergic Rhinitis May be Related to Bacteria Composition in the Nose
Allergic rhinitis, or hay fever, is an allergic condition that affects the nasal area. It is prevalent in older populations, but there exists limited research on physiological changes in the nose as we age. There is evidence, however, that some types of rhinitis can occur after infections that more likely occur after intensive therapies such as surgery and radiation therapy. Generally, the increasing risk of allergic rhinitis in the elderly is believed to be attributed to changes in the bacterial composition in the nasal cavity, which have significant effects on the immune system.
Asthma in the Elderly is Often Overlooked
Asthma is another common disease in the elderly that contributes to their morbidity and mortality. Older patients are often categorized into two groups: those who have had the disease since childhood, and late-onset disease. It remains difficult to correctly diagnose asthma in the latter group, as there are many symptoms that overlap with certain heart conditions and chronic obstructive pulmonary disease. It is also common for older patients to attribute their symptoms to a normal process of aging rather than correctly identifying the disease. Moreover, there is a close link between viral infections and the exacerbation of asthma symptoms and as such, older patients are at high risk of complications as their immune systems deteriorate.
Skin Allergies are Troublesome for an Ageing Population
Skin allergies also affect older patients, since the structural integrity and the functions of skin decline due to aging. Hormonal changes in older adults, especially in females can contribute to the aging of skin. Skin aging leads to various conditions such as dryness, itching, melanoma, and other skin diseases. This is a result of fewer cells in the skin, slower turnover of new skin cells, less lipids, and more permeability.
The aforementioned allergic diseases and conditions afflict older adults and lead to significant morbidities and in some cases, mortality. The process of aging in the context of immune functions is detailed in this review, while presenting multiple allergic diseases that are prevalent in the elderly. Allergic diseases affect between 5 and 10% of the elderly population, and this level seems to be increasing. This concise article summarizes important characteristics and factors for various allergic diseases, all the while providing an important reminder that aging of the immune system is a serious and pervasive problem and will continue, unless we make advancements in the treatment of allergic diseases in the elderly.
Written by Branson Chen, BHSc
Reference: Di Lorenzo G, Di Bona D, Belluzzo F, Macchia L. Immunological and non-immunological mechanisms of allergic diseases in the elderly: biological and clinical characteristics. Immunity & Ageing. 2017 Dec;14(1):23.