Older Adults with Gastrointestinal Infections Display Fewer Symptoms

Enteric infections, or those affecting the gastrointestinal tract, can present differently in older people compared with younger individuals. Symptoms such as pain, vomiting, fever, and bloody diarrhea tend to appear most often in children and young adults, with occurrences declining as patient age increases. This relative dearth of symptoms in the elderly can make it difficult to quickly and correctly diagnose enteric infections. However, it’s crucial that these infections be discovered as soon as possible because the oldest victims have the greatest likelihood of complications and hospitalization.

A team of investigators at the Colorado School of Public Health in Aurora, along with colleagues in Canada, Australia, and the US Centers for Disease Control and Prevention (CDC), analyzed more than 3700 cases of culture-confirmed Campylobacter infection, more than 2700 cases of culture-confirmed nontyphoidal Salmonella infection, and nearly 6900 cases of acute gastroenteritis.

The infections were reported in the US, Canada, and Australia. In all 3 countries, a negative correlation existed between all symptoms reported and older age, with the younger cohorts having the most symptoms and the older cohorts the fewest. The older the patients, though, the greater the chance that they were hospitalized due to infection.

In nonhospitalized patients afflicted with Campylobacter, 85% overall reported experiencing cramps. However, that percentage ranged from a high of 92% among patients aged 5 to 24 years to just 46% of those aged 85 years and up. A full 59% of patients under age 5 experienced bloody diarrhea, while 36% of those between ages 25 and 64 did; in the 75- to 84-year-old cohort, just 18% reported this symptom.

For nonhospitalized patients with Salmonella, the story was similar: 82% of the youngest patients had a history of fever compared with 75% of those between ages 25 and 64, 49% of those between ages 75 and 84, and 39% of those aged 85 years and over.

Hospitalized patients with these infections largely followed the same pattern. For instance, all 9 of those under age 5 who were hospitalized with Campylobacter had cramps, but just 1 out of the 4 people aged 85 and over experienced stomach pains. Significantly higher percentages of young patients hospitalized with Salmonella had bloody diarrhea, cramps, fever, and vomiting compared with older patients.

There was a similar linear negative correlation between symptoms and age in patients with acute gastroenteritis with the exception of bloody diarrhea, which was experienced by just 1% of the subjects under the age of 5 but 5% of the subjects aged 85 and over.

However, the raw number of subjects experiencing bloody diarrhea in those age groups was low to begin with, with just 6 patients in the youngest age group and 2 in the oldest afflicted.

Hospitalization rates for all infections rose in lockstep with patients’ ages. Just 7% of patients under age 5 with Campylobacter needed to be admitted, while 48% of the oldest cohort did. Fewer than 1 in 5 (17%) of the youngest patients with Salmonella were hospitalized, with 49% of those over 85 being admitted. Acute gastroenteritis resulted in fewer hospitalizations overall than Campylobacter or Salmonella, but still 17% of the oldest cohort was admitted versus 1% of the youngest.

How, then, can clinicians discern the severity of gastrointestinal illness in an older adults in the absence of certain symptoms? Because these infections have a higher likelihood of causing complications in elderly people, arriving at a timely diagnosis and avoiding misdiagnosis is key. Fortunately, advances in testing for enteric illnesses may make it easier to arrive at the correct conclusion, although there are caveats.

“Diagnostic testing for gastrointestinal infections has undergone a radical change in the recent years, moving from conventional culture-based to culture-independent testing,” Vaneet Arora, MD, MPH, associate director of clinical microbiology at the University of Kentucky in Lexington, who was not affiliated with the study, told Contagion®. “A vast majority of clinical microbiology laboratories have stopped performing stool cultures and incorporated molecular testing for individual analytes, for example C. difficile or norovirus, or multiplex testing for a panel of varying numbers of analytes that include bacteria, viruses, and parasites.”

This molecular testing offers rapid results and improved sensitivity and specificity; however, the presence of DNA or RNA is not conclusive proof of infection but possibly an indication of colonization, Dr. Arora said.

“Therefore, interpretation of the results should take into account the patient setting and employ clinical judgment.”

Dr. Arora’s recommendation is for a lower threshold for diagnostic testing in elderly patients who are suspected of harboring enteric infections. “What still needs to be done is to have better predictive values for these tests, such that we can say with better confidence that the positive test result is an indication of disease and negative an indication of absence of disease,” he said.

Ms. Saloman is a health writer with more than 20 years of experience working for both consumer-and physician-focused publications. She is a graduate of Brandeis University and the Medill School of Journalism at Northwestern University. She lives in New Jersey with her family.