The Elderly Epidemiology

Despite the fact that the incidence of infective endocarditis has not changed, recent studies have shown remarkable changes in the epidemiology and clinical features of the disease. In the 1950s, when rheumatic fever was prevalent, particularly during World War II and before the wide use of penicillin, the incidence of endocarditis was highest in patients aged 20-30 years old and only 5% of patients with endocarditis were over 60 years of age. More recent publications show that the incidence of infective endocarditis has increased in patients older than 50 years, reaching a peak at 70-74 years of age. Currently, more than 50% of patients are older than 50 years [4-7]. Data from the International Collaboration on Endocarditis (ICE) which encompassed in 2003 over 2,200 well-characterized patients from seven countries with definite infective endocarditis by the Duke criteria, demonstrated that the median age of these patients was 58 years [8]. Hoen et al. [9] performed a population-based survey during 1999 in all hospitals in six French regions representing 26% of the French population (16 million inhabitants). Three hundred ninety adult inpa-tients diagnosed with infective endocarditis according to the Duke criteria were identified. The annual age- and sex-standardized incidence was 31 (95% confidence interval [CI] 28-35) cases per million, not including the region of New Caledonia, which had 161 (95% CI 117-216) cases per million. Incidence increased

Figure 3.1. Incidence of infective endocarditis by age and sex in the study population [9].

15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 90-94

Age (years)

Figure 3.1. Incidence of infective endocarditis by age and sex in the study population [9].

in patients older than 50 years and peaked at 145 cases per million in males between 70 and 80 years (see Figure 3.1). Fefer et al. [10] collected 108 episodes of infective endocarditis during the years 1990-1999 admitted to a community hospital. The annual admission rate was stable at around 0.4 patients with endocarditis per 1,000 admissions. Sixty episodes (56%) involved males and 48 (44%) females, a ratio of 1.3:1. The mean age was 57 (SD 22) years. Thirty-three patients (31%) had prosthetic valve endocarditis and 75 (69%) patients had native valve endocarditis. Patients with prosthetic valve endocarditis were significantly older than those with native valve endocarditis [66 years (standard deviation [SD] 12) versus 54 years (SD 24), P < 0.05].

Selton-Suty et al. [11] studied the characteristics of infective endocarditis in the elderly in a university hospital that is both a referral and a primary care centre. They identified 114 consecutive patients treated for infective endocarditis from 1990 to 1993. Of the 114 patients, 25 (22%) were older than 70 years [mean age 76 (SD 6) years, range 70-91] and 89 were younger than 70 years [mean age 51 (SD 15), range 19-69]. In both groups there was a predominance of males in a ration of 2:1. According to the Duke criteria, the distribution of diagnostic categories was significantly different in the two groups, with a lower percentage of definite infective endocarditis in the older patients. The distribution of underlying heart disease was significantly different between the two groups. Infective endocarditis complicating intracardiac prosthetic devices (valve prostheses or pacemakers) was more common in the older compared to the younger patients. The location of infective endo carditis, when vegetations were seen, was similar in the two groups with most cases involving the mitral valve. There were no significant differences between the two groups with respect to clinical signs, auscultatory findings changes or extracardiac manifestations. Emboli were three times less common in the older patients [2 (8%) vs. 25 (28.1%), P < 0.04]. Echocardiographic findings were also similar between the two groups. Younger patients underwent more surgery operated but this may reflect the reluctance to operate on elderly individuals rather than a true difference related to the actual disease process. To conclude, this detailed investigation demonstrates the clinical significance of infective endocarditis in the elderly. These findings are in accord with other publications demonstrating the increasing prevalence of infective endocarditis in the elderly [8-10].

Why are the elderly more prone nowadays than previously to have infective endocarditis? There are several possible explanations. On the one hand, the wide and early use of antibiotics in proven or suspected infections prevents many cases of endocarditis that were common in the past—when antibiotics were prescribed sparingly. In addition, antibiotic treatment decreased the prevalence of rheumatic heart disease, once the most common predisposing factor for infective endocarditis in younger patients. These factors among others, have contributed to the decline in endocarditis— particularly in the young, but at the same time life expectancy has substantially increased so that the total time a person is at risk for infective endocarditis has increased. Also, as people age, the prevalence of degenerative heart disease increases. The aortic valve undergoes degenerative calcification and such a valve becomes functionally stenotic because of the restricted mobility of the cusps. The resulting turbulence predisposes to endocarditis. As people live now much longer than before, various minor cardiac lesions can become hemodynam-ically important creating turbulent flow and allowing for a fibrin-thrombus clot, the basic mechanism of endocarditis, to form. In addition, in the elderly, hypertension, atherosclerosis and kidney disease are more common allowing for turbulent flow in diseased vessels to develop. Mouth sanitation of the elderly tends to decline with age increasing the risk of local oral infections and subsequent bacteremia, thus increasing the risk of developing infectious endocarditis [12]. The decline in rheumatic infective endocarditis is counterbalanced by the increased prevalence of infective endocarditis due to degenerative valve disease. In addition, prosthetic heart valves are more common in the elderly and the eligible age for cardiac surgery (excluding bypass surgery) is constantly being pushed up [13]. Other medical devices, such as implantable pacemakers, defibrillators and stents, have become more common, increasing the risk of these groups of patients to infectious endocarditis [14,15]. Current data suggest that the prevalence of endocarditis in patients with foreign objects is between that of valvular infective endocarditis in the general population and prosthetic valve infective endocarditis in the range of 550 cases/million patients per year ~100 times more common than non-foreign-body-associated endocarditis [14]. Finally there are some neoplastic diseases that are more common in the aged that may be associated with infectious endocarditis. Among them ulcerating skin cancers (like basal cell carcinoma, melanoma, etc.), polyps and cancers of the large bowel (associated with S. bovis endocarditis). Other factors, such as increasing incidence of nosocomial bacteremia in the elderly and an impaired host immune system, may also contribute to the increase prevalence in the elder. As the world's population is becoming older it is to be expected that in the future more endocarditis cases will be encountered in the very old. In the year 2030, there will be >1 billion individuals > 65 years of age; 19.6% of the North American population, 23.0% of the European population, 11.5% of the Latin American and Asian population and 4.6% of the African population will be elderly; and thus this population will become the prime population segment from which endocarditis cases originate [16]. It is thus expected that the shift in patients with endocarditis belonging to the older age will continue and even increase in the coming decades.

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