Spurious Inferences about Long-Term Outcomes

Abstract

Rationale: Survivors of critical illness suffer significant limitations and disabilities. Objectives: Ascertain whether severe sepsis is associated with increased risk of so-called geriatric conditions (injurious falls, low body mass index [BMI], incontinence, vision loss, hearing loss, and chronic pain) and whether this association is measured consistently across three different study designs. Methods: Patients with severe sepsis were identified in the Health and Retirement Study, a nationally representative cohort interviewed every 2 years, 1998 to 2006, and in linked Medicare claims. Three comparators were used to assess an association of severe sepsis with geriatric conditions in survivors: the prevalence in the United States population aged 65 years and older, survivors' own pre-sepsis levels assessed before hospitalization, or survivors' own pre-sepsis trajectory. Measurements and Main Results: Six hundred twenty-three severe sepsis hospitalizations were followed a median of 0.92 years. When compared with the 65 years and older population, surviving severe sepsis was associated with increased rates of low BMI, injurious falls, incontinence, and vision loss. Results were similar when comparing survivors to their own pre-sepsis levels. The association of low BMI and severe sepsis persisted when controlling for patients' pre-sepsis trajectories, but there was no association of severe sepsis with injurious falls, incontinence, vision loss, hearing loss, and chronic pain after such controls. Conclusions: Geriatric conditions are common after severe sepsis. However, severe sepsis is associated with increased rates of only a subset of geriatric conditions, not all. In studying outcomes after acute illness, failing to measure and control for both preillness levels and trajectories may result in erroneous conclusions.Keywords: severe sepsis; long-term outcomes; geriatric conditions; cohort studies; trajectory bias A substantial body of research has demonstrated that survivors of critical illness face extensive physical, psychological, cognitive, and social deficits in the aftermath of their critical illness (1). For example, survivors of acute respiratory distress syndrome (ARDS) have prolonged 6-minute walk times, executive dysfunction, other neuropsychiatric deficits, and diminished ability to return to work (2-13). Numerous studies have found quality of life among survivors of critical illness (14, 15), severe sepsis (16,17), and ARDS (4-8, 13, 18) to be abnormally low.Patients surviving critical illness have limitations and disabilities somewhat characteristic of an older adult population. Rubenfeld recently postulated a "progeric hypothesis" that the sequelae of critical illness mirror accelerated aging (19). This hypothesis suggests that severe sepsis may be associated with the development of so-called geriatric conditions (15,20,21). These are conditions common among older adults, multifactorial in etiology, and associated with disability, often contributing to decreased quality of life (20-23). The followin...

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