Causes And Risk Factors
Pneumonia is caused primarily by infectious organisms. Pathogens can reach the lungs through inhalation of atmospheric air or can originate in secretions of the upper airways, which travel to the lungs. Rarely, microbes from other parts of the body move to the lungs via the bloodstream (Musher 2012). Although the lungs are constantly exposed to microbes, immune defenses usually prevent infection. However, if immune defenses are impaired (as occurs with age-related immune senescence), then pathogens are more likely to establish an infection (Brandenberger 2016; Simonetti 2014; Krone 2014).
Many infectious organisms can cause pneumonia, but the majority of community-acquired outpatient cases are attributable to the bacteria Streptococcus pneumoniae, Haemophilus influenzae, Legionella pneumophila, Staphylococcus aureus, and Mycoplasma pneumoniae and the influenza, parainfluenza, and respiratory syncytial viruses (Restrepo 2008; Marrie 2005; Cilloniz 2011; Torres 2013).
Pneumonia is categorized based on where it is contracted:
- Community-acquired pneumonia is contracted outside of a hospital or other healthcare facility (ie, in the “community”), and often follows a viral respiratory infection such as a cold or the flu (Musher 2012; UMMC 2012).
- Hospital-acquired pneumonia is contracted during hospitalization. It tends to be more dangerous than community-acquired pneumonia because hospitalized patients generally have weakened immune systems and infectious bacteria found in hospitals have a greater tendency to be antibiotic resistant (UMMC 2012). Mechanical ventilation is a major risk factor for a type of hospital-acquired pneumonia called ventilator-associated pneumonia.
- Healthcare-associated pneumonia affects patients in long-term healthcare facilities or those being treated in healthcare clinics such as kidney dialysis centers. As with hospital-acquired pneumonia, healthcare-associated pneumonia tends to be more serious and involve more dangerous pathogens than community-acquired pneumonia (Mayo Clinic 2015). Some doctors may use the term hospital-acquired pneumonia to encompass all pneumonia contracted via contact with any healthcare facility.
A weakened immune response, such as caused by age-related immune senescence, immunosuppressive medications, or HIV infection, increases pneumonia risk (UMMC 2012; Murray 2015; Krone 2014). People over age 65 are at increased risk of pneumonia (Musher 2012; Mayo Clinic 2015; Loeb 2003). Other pneumonia risk factors include (Musher 2012; Torres 2013; Mayo Clinic 2015; UMMC 2012; Paju 2007; Sura 2012; Lambert 2015):
- Acute infections, such as colds or the flu (For more information on the treatment and prevention of colds and the flu, see the Common Cold and Influenza protocols.)
- Chronic diseases such as:
- Chronic obstructive pulmonary disease (includes chronic bronchitis and emphysema)
- Cardiovascular disease
- Liver disease
- Chronic kidney disease
- Periodontal disease
- Immune deficiency diseases
- Drug or alcohol abuse
- Neurological conditions that interrupt the gag reflex or impair swallowing, such as dementia and stroke
- Use of certain medications, including corticosteroids, immunosuppressants, and proton-pump inhibitors, and overuse of antibiotics resulting in antimicrobial resistance. Proton-pump inhibitors, which are normally used to suppress stomach acidity for relief of gastroesophageal reflux, may be a particularly problematic risk factor for pneumonia because their use is widespread and those who take them may be unaware that they are associated with significantly increased pneumonia risk.