Occupational Attainment as Risk Factor for Progression from Mild Cognitive Impairment to Alzheimer’s Disease: A CREDOS Study

Article type: Research Article

Authors: Myung, Woojae^{a; 1} | Lee, Chunsoo^{a; 1} | Park, Jin Hong^a | Woo, Sook-young^b | Kim, Seonwoo^b | Kim, Sangha^a | Chung, Jae Won^a | Kang, Hyo Shin^c | Lim, Shinn-Won^{a; c} | Choi, Junbae^a | Na, Duk L.^d | Kim, Seong Yoon^e | Lee, Jae-Hong^f | Han, Seol-Heui^g | Choi, Seong Hye^h | Kim, Sang Yunⁱ | Carroll, Bernard J.^j | Kim, Doh Kwan^{a; *}

Affiliations: [a] Department of Psychiatry, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea | [b] Biostatistical Team, Samsung Biomedical Research Institute, Seoul, Korea | [c] Center for Clinical Research, Samsung Biomedical Research Institute, Seoul, Korea | [d] Department of Neurology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea | [e] Department of Psychiatry, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea | [f] Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea | [g] Department of Neurology, Konkuk University School of Medicine, Seoul, Korea | [h] Department of Neurology, Inha University School of Medicine, Incheon, Korea | [i] Department of Neurology, Seoul National University College of Medicine, Seoul, Korea | [j] Pacific Behavioral Research Foundation, Carmel, CA, USA

Correspondence: [*] Correspondence to: Doh Kwan Kim, MD, PhD, 50 Irwon-dong, Kangnam-gu, Seoul 135-710, Korea. Tel.: +82 2 3410 3582; Fax: +82 2 3410 0941; E-mail: paulkim@skku.edu.

Note: [1] These authors contributed equally to this work.

Abstract: High occupational attainment has been known as a marker of cognitive reserve. Previous studies in the general population have shown that high occupational attainment is associated with reduced risk of Alzheimer’s disease (AD). However, few studies have assessed the effect of occupational attainment on the clinical course of mild cognitive impairment (MCI). In this study, we evaluated whether individuals with high occupational attainment show more frequent progression from MCI to AD. Participants (n = 961) with MCI were recruited from a nationwide, hospital-based multi-center cohort, and were followed for up to 60 months (median: 17.64, interquartile range [12.36, 29.28]). We used Cox regression for competing risks to analyze the effect of occupational attainment on development of AD, treating dementia other than AD as a competing risk. Among the 961 individuals with MCI, a total of 280 (29.1%) converted to dementia during the follow-up period. The risk of progression to AD was higher in the individuals with high occupational attainment after controlling for potential confounders (hazard ratio = 1.83, 95% confidence interval = 1.25–2.69, p = 0.002). High occupational attainment in individuals with MCI is an independent risk factor for higher progression rate of MCI to AD. This result suggests that the protective effect of high occupational attainment against cognitive decline disappears in the MCI stage, and that careful assessment of occupational history can yield important clinical information for prognosis in individuals with MCI.

Keywords: Alzheimer’s disease, mild cognitive impairment, occupational attainment, progression

DOI: 10.3233/JAD-160257

Journal: Journal of Alzheimer's Disease, vol. 55, no. 1, pp. 283-292, 2017