en مطالعات سالمندی Aging Studies پژوهشي Original Research Articles <div style="text-align: justify;"><strong>Objectives</strong>: Dementia is the fifth cause of death in older adults with the most significant financial, social, and caring burden on health systems across the world. The aim of this study was to determine the most common medical risk factors for dementia in the retired population.<br> <strong>Methods</strong>: A case-control methodology was used for this study, within which 180 patients with dementia were compared to 371 controls for medical risk factors in the National Iranian Oil Company (NIOC) in 2017. Participants in the case and control groups were matched in terms of age, educational level, and sex. The logistic regression was employed to estimate Odds Ratios (OR), using SPSS software.<br> <strong>Results</strong>: The majority of the participants were male (55%) and married (69%) with a mean age of 73.14 (SD=9.11) and high school education (38%). The results of the adjusted logistic regression showed a significant association among dementia and chronic and acute vitamin D3 deficiency (more and less than 1 year) (OR=4.73, P<0.001, OR=7.50, P<0.001, respectively), cancer history (OR=15.31, P<0.001), and chronic anemia (OR=5.95, P<0.001).<br> <strong>Discussion</strong>: The results of this study suggest vitamin D3 deficiency, cancer, and anemia history as probable risk factors for dementia. Thus, managing or controlling these risk factors may effectively delay or prevent the onset of dementia for the individuals.</div> Dementia, Risk factors, Older adults, NIOC 377 384 http://irj.uswr.ac.ir/browse.php?a_code=A-10-799-3&slc_lang=en&sid=1 Hossein Ghasemzadeh hghassem361@gmail.com @gmail.com 0000-0003-1400-4099 Yes Department of Ageing, Research Center on Ageing, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. Ahmadali Akbari Kamrani akbarikamrani@yahoo.com 0000-0003-2995-9031 No Department of Ageing, Research Center on Ageing, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. Yadollah Abolfathi Momtaz drmomtaz@gmail.com 0000-0003-1939-1470 No Department of Ageing, Research Center on Ageing, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. Mehdi Rassafiani mrassafiani@yahoo.com 0000-0003-4093-6113 No Department of Ageing, Research Center on Ageing, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. Fatemeh Nourhashemi Fnourhashemi@gmail.com 0000-0003-4029-9433 No Department of Ageing, Research Center on Ageing, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. Robab Sahaf robabsahaf@gmail.com 0000-0002-6785-3708 No Department of Occupational Therapy, Faculty of Allied Health Sciences, Kuwait University, Kuwait.