Purpose Research about the prevalence of dementia among older adults in the incarceration system is currently lacking, and further investigation is warranted. Considering the high level of healthcare needs, unique behavioural issues and difficulty to rehabilitate within the system due to its punitive approach and lack of effective rehabilitation programs, further investigation is warranted to characterize and determine the number of incarcerated older adults with dementia. The purpose of this study is to estimate the prevalence of individuals with dementia in the prison system while also describing the incarceration, demographic and offence-related characteristics of this unique population. Design/methodology/approach South Carolina (SC) Alzheimer’s Disease and Related Dementias Registry (1992–2016) and South Carolina Department of Corrections (SCDC) data (Fiscal years 1992–2019) were cross-referenced. The prevalence of Alzheimer’s disease and related dementias (ADRD) cases in the corrections system was calculated using South Carolina Alzheimer's Disease (SC AD) SC ADRD Registry and SCDC data. Pearson’s correlation coefficients were calculated to determine strength and direction of relationships between year of incarceration and frequency of ADRD cases both prior to and after incarcerations, respectively. Significant differences by age group, race, gender and dementia type were determined using a two-tailed pooled t-test and Bonferroni approach where appropriate. Count data for types of crimes committed are also presented. Findings The linkage showed that there were 2,171 individuals within the SC AD Registry who have been in the corrections system, about 1% of those in the Registry. Of these individuals, 1,930 cases were diagnosed with ADRD after incarceration and 241 prior to incarceration. In 2016, 317 individuals with ADRD were incarcerated. For ages 55 and above in South Carolina, the prevalence of ADRD is 6.7% in the general, non-incarcerated population compared to 14.4% in the incarcerated population. Additional results showed that those diagnosed with ADRD between 55 and 65 years of age had a significantly lower mean age at first incarceration (34.6 years of age) than those diagnosed between 66 and 74 years of age (55.9 years of age), indicating that those incarcerated earlier in life had an earlier dementia diagnosis. Additionally, African Americans had a significantly lower mean age at first incarceration (43.4 years of age) than Whites (46.2 years of age) and females had significantly lower mean age at first incarceration (42.9 years of age) than males (45 years of age). When investigating trends, results showed a significant positive linear association between year and frequency of ADRD diagnoses (p-value < 0.05) for those with ADRD diagnosis prior to incarceration and a significant decreasing linear association (p-value < 0.0001) in the number of individuals with an ADRD diagnosis after corrections. Findings also showed that a large percentage of older adults with ADRD in prison did not commit a violence offence. Originality/value This study links a population-based Alzheimer’s disease registry and state-wide corrections data to estimate the prevalence of individuals with dementia in the prison system. This linkage presents an opportunity to fill in significant gaps and contribute to the body of literature on dementia among people in prison in the USA.

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