Scd in a population-based sample: Progression to MCI

Abstract

Subjective cognitive decline (SCD) is a popular topic for investigation in individuals who are cognitively normal (CN). A major question concerns its ability to predict subsequent cognitive decline after controlling for relevant variables in the general population. The Mayo Clinic Study of Aging is a population-based random sample of non-demented individuals aged 70 to 89 years at the time of enrollment, between 2004 and 2011, while residing in Olmsted County, Minnesota. At enrollment, five questions from the Blessed Memory Inventory were asked of each participant, and a 10-point scale was constructed, reflecting the individuals’ concerns about their cognitive function. The SCD score was dichotomized into any versus none subjective cognitive complains. Participants were re-evaluated every 15 months for clinical status. Published criteria for CN, mild cognitive impairment (MCI) and dementia were applied at each visit with the evaluators blinded to previous diagnoses and clinical data. At baseline and each follow-up visit, information was obtained from the Clinical Dementia Rating Scale, Neuropsychiatric Inventory, Functional Activities Scale, as well as cognitive function on a standard neuropsychological battery (memory, attention/concentration, language and visuospatial skills), data on medical comorbidities and APOE genotype. We assessed the relationship between any subjective memory complaints and risk of MCI using Cox proportional hazards models. There were 2,061 CN participants who had data on SCD and had at least one follow-up visit. The median follow-up was 3.9 years and 525 developed MCI. Approximately 79 percent of the sample expressed some concern about their cognition. Among those individuals with no cognitive concerns was 4.73 percent developed MCI compared to 7.32 percent in those with some cognitive concern. After controlling for age, education, sex, ApoE4 carrier status, depression/dysphoria, anxiety, attention, memory, global cognition and medical comorbidities, any cognitive complaint predicted progression to MCI (HR=1.35 (95% CI: 1.05-1.73, p = 0.018)). SCD predicts clinical progression to MCI in a population-based sample after controlling for relevant contributing factors. The construct of SCD might be useful in selecting individuals for pre-clinical intervention trials.