‘Inflamm-aging’ by Seniors May Impact Pneumonia Susceptibility

Antibiotic treatment alone may not be sufficient to treat pneumonia in older adults, says a study by researchers of the Michael G. DeGroote Institute for Infectious Disease Research at McMaster University. In fact, it appears as though the inflammation that comes naturally with age actually increases the risk of developing pneumonia.

“It sounds counterintuitive to limit inflammatory responses during a bacterial infection, but clinical observations and our research indicates anti-bacterial strategies need to be tailored to the age of the patient,” said Dawn Bowdish, lead author of the paper published in the journal PLOS Pathogens today. She is an associate professor for pathology and molecular medicine, and a scientist of the institute.

Aging is accompanied by a chronic state of low-level inflammation — sometimes called ‘inflamm-aging’ — which is associated with diseases such as cardiovascular disease, dementia and infections, particularly pneumonia. During an infection a little bit of inflammation is required to fight the infection; however, in older adults the inflammation, which is already heightened, increases during infection but doesn’t necessarily go away afterward. Exposure to these high levels of inflammation appears to impair the ability of white blood cells to fight infection.

In the study, the researchers determined that the higher levels of inflammation found in the blood of old mice caused some types of white blood cells to enter the bloodstream before they were fully mature and produce even more inflammation.

Although small amounts of inflammation are required to fight infection, the old mice produced so much that their white blood cells were less effective. Reducing levels of inflammation in the young mice had no effect but reducing levels in the old mice helped them to clear the infection and get better.

The research follows a 2015 McMaster study that showed that older adults with pneumonia do better when given drugs, such as corticosteroids, to reduce inflammation in addition to antibiotics.

“Our study in mice is consistent with clinical studies that recommend using anti-inflammatories as part of treatment to improve older adults’ defence against pneumonia, and that points to the development of better care,” said Bowdish.

The study was funded by the Canadian Institutes for Health Research (CIHR), an Ontario Early Researcher Award and a Pfizer-Aspire Research Award.