Prevention of Tuberculosis in Older Adults in the United States: Obstacles and Opportunities

An estimated 32% of the world's population, or 1.86 billion people, is infected with Mycobacterium tuberculosis, and >8 million new cases of tuberculosis disease occur annually [1]. Older adults (persons ≥65 years of age) comprise the fastest-growing sector of the global population, and represent 12% of the current US population, a proportion that is expected to increase to 20% by the year 2050 [2]. Molecular studies of tuberculosis patients in Florida found that compared to younger persons, older adults were significantly less likely to be part of a case cluster; this suggests that their tuberculosis disease was due to reactivation of latent tuberculosis infection [3]. Some researchers have theorized that waning immunity in older adults predisposes to an increased rate of progression from latent tuberculosis infection to reactivation tuberculosis disease [4], but such declines in immunocompetence with age have not been convincingly demonstrated [5]. Older adults living in long-term care facilities have historically had higher rates of tuberculosis disease than those living in the community [4, 6]. In 1984–1985 in 29 US states, the incidence rate was 39.2 per 100 000 persons for older adults in long-term care facilities and 21.5 per 100 000 for older adults in the community, compared with 9.2 per 100 000 for all age groups in 1984 [7, 8]. In Arkansas at that time, 20% of the tuberculosis disease cases in older adults occurred in the 5% of older adults in long-term care facilities [5]. In the United States, approximately 5% of older adults reside in long-term care facilities [7, 9]. Because the resident population of older adults in such facilities is at increased risk of reactivation tuberculosis disease, other residents in this setting are therefore at risk for outbreaks of primary tuberculosis disease that is the consequence of transmission from a source case with reactivation tuberculosis disease [4, 10]. Tuberculosis disease in older adults is of particular concern given the high tuberculosis mortality rates in this group. In Hong Kong, reported mortality rates ranged from 4.8% in those aged 60–69 years (compared with 0.2% in those 20–39 years of age) up to 19.9% in those ≥80 years; others report rates of 50% in those ≥80 years [11, 12]. In the United States in 1979 and 1998 alike, death rates from tuberculosis disease for persons aged ≥85 years were 10 times higher than for the population as a whole [13]. Between 1993 and 2008, 7% of younger persons and 21% of older persons (including 42% of older persons in long-term care facilities) died while receiving tuberculosis disease therapy [10]. This increased mortality underscores the importance of preventing tuberculosis disease in older adults. The population of older adults in need of long-term care is predicted to rise from 8 million in 2000 to 19 million in 2050 [14]. Although there is a decreasing risk of latent tuberculosis infection in successive birth cohorts, the need to prevent tuberculosis disease in older adults and in older adults living in long-term care facilities in particular, will remain important over the coming decades [15]. In this report, we calculate rates and ratios of tuberculosis disease in subgroups of older adults in the United States and examine trends over time to gain a clearer understanding of risk factors for tuberculosis disease in this population and to elucidate potential intervention strategies.