Tuberculosis in the elderly. Epidemiology and optimal management

The problem with the emergence of HIV-associated tuberculosis (which usually occurs in young adults) is that attention has been diverted away from the fact that, in the developed world, the elderly represent the biggest pool of tubercular disease and therefore the greatest pool of infection within the community. Although the incidence rate of tuberculosis continues to decline in most countries, there is evidence from parts of the developing world that rates may be beginning to increase. The presentation of the disease in the elderly is often uncharacteristic, e.g. disease tending to be more insidious in onset, pyrexia often absent and haemoptysis less common. Chest x-ray changes may also mislead the clinician in that disease is frequently present in the mid or lower zones. The elderly are probably at greater risk of extrapulmonary tuberculosis, which also presents in uncharacteristic ways. The diagnosis remains based on clinical presentation and the presence of smear and culture positivity, although some patients may be treated in the absence of microbiological proof. Standard treatment is with a combination of isoniazid, rifampicin and pyrazinamide, with or without a fourth drug such as ethambutol. The incidence of adverse effects in the elderly is much greater than that in younger patients, often resulting in the need to change the medication to drugs which are better tolerated. This may require changing to regimens which are less effective and therefore have to be taken for a longer period of time. The presence of concomitant disease such as liver or renal failure may also necessitate the administration of a suboptimal regimen. Mortality in elderly patients with tuberculosis is considerably higher than that in younger patients, even when treatment appears to have been started on time; even in the developed world mortality exceeds 30% in those patients over 70 years of age.