Science

Rosebud O. Roberts, MB, ChB, MS
Ruth H. Cha, MS
Michelle M. Mielke, PhD
Yonas E. Geda, MD, MSc
Bradley F. Boeve, MD
Mary M. Machulda, PhD,LP
David S. Knopman, MD
Ronald C. Petersen, MD,PhD

Individuals aged 85 years and older are the most rapidly growing group in the United States and worldwide. Studies of the oldest old are difficult to conduct and to interpret. Persons aged 90 years and older typically have sensory losses, difficulty providing valid and reliable information, high comorbidity, and a high prevalence of dementia; most are typically women. Often, factors asso-ciated with risk of cognitive impairment at younger ages are no longer predictive, raising the possibility that multiple coexisting diseases might be more predictive than solitary diseases. Because many individuals aged 90 years and older already have early stages of mild cognitive impairment (MCI), studies are often cross-sectional and can only assess risk of dementia or Alzheimer disease (AD). Furthermore, potential interventions at these ages may have limited long-term benefit. The goal of this study was to identify risk and protective factors for incident MCI among cognitively normal persons aged 85–89 years at enrollment to the Mayo Clinic Study of Aging (MCSA).