Temporal trends in cognitive function of older US adults associated with population changes in demographic and cardiovascular profiles

• Type of Material: Article
• Authors: Michael Bancks, Wake Forest University; Alvaro Alonso, Emory University; Norrina Allen, Northwestern University; Kristine Yaffe, University of California San Francisco; Mercedes Carnethon, Northwestern University
• Language: English
• Date: 2019-07-01
• Publisher: BMJ Publishing Group
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © Author(s) (or their employer(s)) 2019.
• License: Creative Commons Attribution-NonCommercial 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1136/jech-2018-211985
• Title of Journal or Parent Work: Journal of Epidemiology & Community Health
• Volume: 73
• Issue: 7
• Start Page: 612
• End Page: 618
• Grant/Funding Information: MB was supported by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health under Award Number T32HL069771 to conduct the current work while at Northwestern University in Chicago, Illinois, USA.; AA was supported by the NHLBI of the National Institutes of Health under Award Number U01HL096902.
• Keywords: Life Sciences & Biomedicine; Prevalence; Public, Environmental & Occupational Health; Risk; Science & Technology; Impairment; Health; Dementia; United States; School quality; Alzheimer's disease
• Research Categories: Health Sciences, Epidemiology; Biology, Neuroscience; Biology, Biostatistics

Abstract

Background: Recent estimates suggest that dementia incidence is decreasing in the US possibly due to better management of cardiovascular disease (CVD) risk factors, but these studies lack repeated cross-sectional assessment among a representative US sample. Our objective was to assess temporal trends in cognitive performance in relation to CVD risk factors among older National Health and Nutrition Examination Survey (NHANES) participants. Methods: We used repeated cross-sectional assessment of 5711 participants ≥60 years of age from four NHANES cycles: 1999-2000, 2001-2002, 2011-2012 and 2013-2014. Cognitive function was assessed during each cycle with the Digit Symbol Substitution Test (DSST). We estimated mean DSST score at each cycle and annual trend in DSST before and after adjustment for age, sex, race/ethnicity, education, smoking status, blood pressure, glucose status and body mass index. Results: DSST scores was significantly higher for 2011-2012 (difference: 6.7, 95% CI 4.4 to 9.0) and 2013-2014 (difference: 6.2, 95% CI 4.0 to 8.5), but not 2001-2002 (difference: 2.3, 95% CI -0.01 to 4.6) as compared with 1999-2000 before adjustment. We observed a linear trend for higher annual DSST score before adjustment (DSST/year: 0.44, 95% CI 0.31 to 0.57) and after adjustment for age, sex, race/ethnicity, educational attainment and CVD risk factors (DSST/year: 0.17, 95% CI 0.08 to 0.26). Educational attainment was most strongly associated with the attenuation in the trend in cognitive function (77% of trend attenuation and 20% of variance in DSST). Conclusion: Cognitive function is improving over time for US adults aged ≥60 years. These improvements are strongly associated with greater educational attainment and irrespective of the changing US demographic and cardiovascular health profiles.