Tuberculosis in the elderly

During the past 25 years, the age distribution of tuberculosis (TB) in the United States has shifted remarkably from younger age to the later decades, ie, in persons over 70 years of age. Elderly persons, although infected many years ago, exhibit a positive tuberculin reaction in only 20% to 25% upon entry into nursing homes. Among members of this infected elderly population, case rates as high as 500 to 1,000 per 100,000 population are found. Endogenous breakdown of older lesions is the common mechanism for the development of the disease. Of the remaining 70% to 80% tuberculin-negative population, 10% are immunoincompetent and die soon upon entry into the nursing home. The remaining 90% of the nonreactors who survive are again susceptible to new infection. The point prevalence of positive tuberculin reactors approximately doubles after more than a 6 months stay at the nursing home. This inadvertent exposure usually occurs in the nursing home due to reactivation of old lesions among old reactors. Although 5% of persons over 65 years of age live in nursing homes, they account for 20% of TB cases. This gives a rate four times greater than the rate among the elderly living at home, or twelve times greater than in persons 40 to 60 years of age. In Arkansas, more than 53% of active cases occurred in persons over 65 years of age, who account for only 14% of the population. Diagnosis of TB in the elderly may be considerably delayed or even totally missed.(ABSTRACT TRUNCATED AT 250 WORDS)