Severe Sepsis and Cognitive Impairment and Functional Disability

Cognitive and physical impairment have a major impact on caregiving needs and on healthcare costs to society; the onset of disability is associated with worsened mortality and increases in medical costs for years. The costs put a disproportionate strain on both Medicare and Medicaid.

According to researchers, it is thought that of the patients with severe sepsis in the United States, “many are discharged with a new—but poorly defined—constellation of cognitive and functional impairment.” Although severe sepsis is a common noncardiac cause of critical illness, the long-term impact of severe sepsis on cognitive and physical impairment is not well documented. The researchers recently conducted a prospective cohort study to determine the change in cognitive impairment and physical functioning in survivors of severe sepsis, controlling for their presepsis functional levels. They reported results of the study in the Journal of the American Medical Association [2010;304(16):1787-1794]. Data were drawn from the Health and Retirement Study, a nationally representative survey of US residents (1998-2006).

From a cohort of 9223, respondents had a baseline cognitive and functional assessment and had linked Medicare claims. Of those, 516 survived severe sepsis and 4517 survived a nonsepsis hospitalization to at least 1 follow-up survey. The 516 survivors of severe sepsis were the primary cohort for the current analysis. The patients were followed up for as many as 4 surveys (7.8 years) of data prior to severe sepsis and as many as 4 surveys (8.3 years) following severe sepsis. The primary outcome measures were the presence of cognitive impairment and the number of activities of daily living (ADLs) and instrumental activities of daily living (IADLs) for which patients required assistance.

Using validated surveys, personal interviews were conducted with the respondents or proxies for assessment of the end points. Ninety-day mortality after severe sepsis was 41.3% (95% confidence interval [CI], 38.8%-43.8%); 5-year mortality was 81.9% (95% CI, 79.8%-84.0%). Among survivors of severe sepsis, there was a clinically and statistically significant association between incident severe sepsis and moderate-to-severe cognitive impairment: 6.1% (95% CI, 4.2%-8.0%) of eventual survivors had moderate-to-severe cognitive impairment just prior to the sepsis compared with 16.7% (95% CI, 13.8%-19.7%) at the first survey following the sepsis (P<.001). The incidence of severe sepsis remained highly associated with progression to moderate-to-severe cognitive impairment in fixed-effects regression.

There was a high rate of new functional limitations seen after sepsis: in patients with no limits prior to sepsis, there was a mean 1.57 new IADL and ADL limitations following sepsis (95% CI, 0.99-2.15) and a mean 1.50 new IADL and ADL limitations (95% CI, 0.87-2.12) for those with mild-to-moderate limitations before sepsis. There was no change in moderate-to-severe cognitive impairment in general hospitalizations with no sepsis. For patients who had an acute increase in the number of functional limitations, sepsis was also associated with an increased rapid rate of developing additional limitations thereafter, at 0.51 new limitations per year (P=.007 for difference vs baseline). Patients with already poor functioning did not experience a statistically significant change in functioning. In conclusion, the researchers noted that “severe sepsis in this older population was independently associated with substantial and persistent new cognitive impairment and functional disability among survivors. The magnitude of these new deficits was large, likely resulting in a pivotal downturn in patients’ ability to live independently.”