The research, conducted by the University of Michigan and supported primarily by the National Institute on Aging (NIA), part of the NIH, appears in the Oct. 27, 2010, issue of the Journal of the American Medical Association.
Theodore J. Iwashyna, M.D., Ph.D., and colleagues found that an older person's risk of cognitive decline increased almost threefold following hospitalization for severe sepsis. They also found that severe sepsis was associated with greater risk for the development of at least one new limitation in performing daily activities following hospitalization.
"Sepsis is common in older people and has a high mortality rate," said NIA Director Richard J. Hodes, M.D. "This study shows that surviving sepsis may bring substantial and under-recognized problems with major implications for patients, families and the health care system."
In sepsis, immune system chemicals released into the blood to combat serious infection trigger widespread inflammation. This can lead to low blood pressure, heart weakness, and organ failure. Anyone can get sepsis, but infants, children, older people, and those with weakened immune systems are most vulnerable. People with sepsis often receive treatment in hospital intensive care units to combat the infection, support vital organs and prevent a drop in blood pressure.
"This study should help change the way we think about severe sepsis," said Iwashyna. "We usually think of severe sepsis as a medical emergency and focus our efforts on making sure the patient survives. This study shows that survivors often have severe problems for years afterwards."
Using data from the NIA-supported Health and Retirement Study (HRS), the researchers analyzed the cognitive and physical function of older people before and after hospitalization for severe sepsis. The HRS is a long-term study that collects information on the health, economic and social factors influencing the health and well-being of a nationally representative sample of Americans over age 50. Study data on participants 65 and older are linked to Medicare claims data to enable detailed analysis of medical conditions and health status.
The scientists analyzed Medicare claims data from 516 people who survived 623 hospitalizations for severe sepsis between 1998 and 2005. The average age of participants was 77 at the time of hospitalization. The researchers also examined the individuals' HRS data on cognitive function, measured through standard tests. Physical limitations were measured by the need for assistance in six activities of daily living basic self-care tasks (walking, dressing, bathing, eating, toileting and getting into and out of bed) and five instrumental activities of daily living (preparing a hot meal, shopping for groceries, making telephone calls, taking medicines and managing money), which are associated with the ability to live independently. For comparison, the researchers analyzed Medicare and HRS data on 4,517 survivors of 5,574 non-sepsis general hospitalizations during this time period.
Almost 60 percent of hospitalizations for severe sepsis were associated with worsened cognitive and/or physical function among survivors in the first survey following hospitalization. The risk of progression to moderate or severe cognitive impairment in sepsis survivors was 3.33 times higher than their risk before hospitalization. Severe sepsis was associated with the development of 1.57 new functional limitations among patients with no limitations before sepsis. In contrast, patients who did not develop sepsis and had no functional limitations before hospitalization developed an average of 0.48 new functional limitations. Non-sepsis hospital admissions were not associated with an increased risk for cognitive decline.
"This is one of more than a thousand research papers that have used Health and Retirement Study data," said Richard Suzman, Ph.D., director of the NIA's Division of Behavioral and Social Research, which supports the HRS. "The uniquely rich HRS dataset enabled the analysis of both cognitive and physical function in relation to hospitalization for a very specific medical condition. I look forward to the investigators refining their findings in the future."
The HRS, now in its 18th year, follows more than 22,000 people over the age of 50, collecting data every two years, from pre-retirement to advanced age.