Aging increases susceptibility to disease

What makes it so dangerous?

Both the incidence and mortality of infections increase with age. The reason for this is the age-related impairment of the immune system. Infectious diseases often take an atypical course in old age, which makes early diagnosis and therapy difficult. Due to the age-associated weakness of the immune system, septic courses are common. The elderly are just as susceptible to infection as therapeutically or immunosuppressed patients due to their underlying disease.

The human organism is colonized and surrounded by microorganisms. The ratio of bacteria to the body's own cells is about 10: 1 (Fig. 1). Our physiological bacterial flora, especially the intestinal flora, is essential for the development of our immune system and protects us from being colonized by pathogenic microorganisms [5]. However, some physiological residents can become pathogenic when the immune system is weakened.

With age, the immune system loses its efficiency both with regard to the control of invading pathogens and with regard to the elimination of malignantly transformed endogenous cells. The immune system is also increasingly losing the ability to differentiate between "self" and "foreign". For this reason, the prevalence not only of infections and malignancies but also of autoimmune diseases increases with age.

In addition, in old age the decline in various body functions (e.g. reduced coughing), concomitant diseases (e.g. impaired swallowing function after a cerebral infarction, polyneuropathy in diabetes mellitus) and drug side effects contribute to the increased susceptibility to infections (Table 1).

Diagnostic problems

Infections are often atypical in old age: the infection manifests itself in a non-specific functional disorder, the urinary tract infection manifests itself e.g. B. as incontinence, pneumonia as confusion. In elderly patients with an unexplained rapid loss of function (motor or cognitive), the attending physician must consider the possibility of a serious infection (see also Table 2). Infections in old age often have a silent course: the infection remains asymptomatic / few symptoms for a long time, is diagnosed late and is difficult and complex. A classic example of this is appendicitis in old age, the mortality of which is 15 to 20 times higher than that of adolescents and young adults. In addition, the "pseudo-silent" course must also be considered in old age: in particular in the case of lamenting and / or multimorbid old patients, symptoms are incorrectly attributed to the normal aging process and not to an infection ("the disease screams, only the doctor is deaf for it") [10].

The diagnosis of an infection in old age is made even more difficult because fever occurs less often in old age or older patients develop a less pronounced increase in temperature than young adults. Even with sepsis, fever may be absent [10]. Leukocytosis and a shift to the left in the peripheral blood are not infrequently absent as an expression of the low bone marrow reserve. In contrast, the C-reactive protein is a sensitive indicator for a systemic infection with bacteria and fungi. However, since the C-reactive protein also increases in autoimmune processes, it is not very specific. However, a normal C-reactive protein largely rules out systemic infection (exception: in the first 12-24 hours). An elevated procalcitonin is more specific than the C-reactive protein in the diagnosis of systemic infections by bacteria and fungi and rises somewhat earlier.

In addition to taking body fluid and secretions from the affected organ for microbiological diagnostics (Fig. 2), blood should be taken to create cultures in order to identify bacteremic (septic) processes. The cultivation of a pathogen from lege artis blood cultures is of high diagnostic specificity.

The most common infections in general practice

The most common infections in old age are urinary tract infections, followed by respiratory infections and skin, soft tissue and wound infections. The most common life-threatening infections are pneumonia, while urinary tract infections including urosepsis, on average, have a better prognosis. The mortality of almost all infections increases with age. In addition to a possible delay in diagnosis and the tendency to develop septic disease, the reasons for this are the reduced functional reserves of numerous body functions, especially breathing and kidney excretion, the high number of multi-resistant pathogens, the multimorbidity in old age and the side effects of treatment, including the occurrence of C. difficile Infections.


The incidence of out-of-hospital acquired pneumonia is approximately 50 times higher in those over 75 years of age than in young adults. It is slightly higher in men than in women [3].

While fever, chills, chest pain, limb pain and headache are less common in old people than in young people, tachypnea occurs earlier and more frequently in old people due to the restricted functional reserve of the lungs [9].

The prevention of pneumonia in old age includes the annual flu vaccination, the one-time vaccination against pneumococci after the age of 60 (both vaccinations are recommended by the Standing Vaccination Commission of the Robert Koch Institute), the early diagnosis and treatment of swallowing disorders, an adequate, Food intake to avoid undernourishment and malnutrition as well as physical measures (e.g. breathing exercises, consistent mobilization, inhalations, vibration massage).

The incidence of tuberculosis also increases significantly beyond the age of 65. These are mainly reactivations after the first infection in children and adolescents. a. during and after World War II. That is why the pathogens causing most tuberculosis diseases in old people are sensitive to the usual first-line tuberculostatics.

Urinary tract infections

Over 15% of women and around 10% of men over 70 years of age who live at home suffer from bacteriuria (> 10,000 bacteria / ml urine). These numbers are considerably higher in nursing homes (women 25-50%, men 15-40%).

Asymptomatic bacteriuria is not treated with antibiotics. About 2/3 of all old patients with a urinary catheter have a fever due to a urinary tract infection. A urinary tract infection often causes unspecific symptoms. Symptomatic urinary tract infections must be treated with antibiotics.

Endocarditis and meningitis

Bacterial endocarditis and meningitis are less common infections. Endocarditis is often associated with unspecific symptoms such as weakness, weight loss, joint problems and thrombosis. It is particularly difficult to diagnose in old age because heart murmurs from other causes, especially valve calcifications, are not uncommon in old age. Conversely, in the case of endocarditis, especially at the onset of the disease, the heart murmur may be absent. The pathogen detection in the blood culture and the transesophageal echocardiography are decisive for the diagnosis.

In bacterial meningitis, which is most commonly caused by pneumococci, fever and neck stiffness are often absent in old age. Conversely, neck stiffness is sometimes simulated by Parkinson's syndrome or degenerative changes in the cervical spine. Often unspecific symptoms such as confusion or clouding of consciousness appear at an early stage. For the definitive diagnosis (or exclusion) of meningitis, cerebrospinal fluid removal is required [7]. If the contraindications (especially blood clotting disorders) are observed, lumbar cerebrospinal fluid removal is a procedure with few complications in old age [2].

Herpes zoster

As a rule, the primary infection with the chickenpox virus (varicella-zoster virus, VZV) already takes place in childhood, and the virus persists in sensitive spinal and cranial nerve ganglia. The frequency of reactivation in the form of herpes zoster increases with age. VZV can (as a reactivation and as a primary infection) cause myelitis, encephalitis (especially cerebellitis), cerebral vasculitis (with cerebral infarction) and meningitis, which sometimes go hand in hand without VZV-typical skin changes.

The frequency of the very painful and difficult to treat post-herpetic neuralgia also increases with age [4]. To reduce the frequency of post-zoster neuralgia and to prevent other complications, herpes zoster should be treated systemically with acyclovir or another effective antiviral agent at an early stage. Intravenous treatment with acyclovir is required in immunocompromised patients with facial or central nervous system involvement.

Intestinal infections caused by Clostridium difficile

In recent years there has been a sharp increase in the number of potentially life-threatening intestinal infections caused by C. difficile. Elderly people are particularly at risk: around half of the patients with symptomatic C. difficile infection are 75 years of age or older [8]. In the vast majority of cases, the disease is preceded by therapy with antibiotics, which damage the normal intestinal flora so that C. difficile can spread in the intestine. C. difficile infections pose particular hygiene problems because the spores remain viable for several years and cannot be killed by common disinfectants.

The classic therapy consists of oral administration of vancomycin. Orally administered fidaxomicin reduces the frequency of recurrence compared to vancomycin [6]. We do not recommend oral administration of metronidazole in elderly people due to numerous drug interactions and side effects. The last resort is the transplantation of stool from healthy donors who have not been treated with antibiotics.

Conclusion: Infections in old age are common

The elderly are just as susceptible to infections as patients who are therapeutically or immunocompromised because of their underlying disease.

Bacterial infections in the elderly must be treated early with antibiotics, and depending on the location, also surgically.

Prophylactic use of antibiotics in the elderly should be rejected (selection of resistant pathogens, increased risk of C. difficile infections).

The following are necessary to prevent infections:
  • Adequate nutrition
  • Avoidance of immobility or early mobilization
  • Diagnosis and treatment of swallowing disorders
  • Early removal of urinary catheters and venous access
  • Vaccinations (influenza, pneumococci)

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Geriatric Center Evangelical Hospital Göttingen-Weende & Institute for Neuropathology, University of Göttingen

Conflicts of Interest: The author has not declared any.