Association of Race and Ethnicity With Incidence of Dementia Among Older Adults

Abstract

Importance: The racial and ethnic diversity of the US, including among patients receiving their care at the Veterans Health Administration (VHA), is increasing. Dementia is a significant public health challenge and may have greater incidence among older adults from underrepresented racial and ethnic minority groups.

Objective: To determine dementia incidence across 5 racial and ethnic groups and by US geographical region within a large, diverse, national cohort of older veterans who received care in the largest integrated health care system in the US.

Design, setting, and participants: Retrospective cohort study within the VHA of a random sample (5% sample selected for each fiscal year) of 1 869 090 participants aged 55 years or older evaluated from October 1, 1999, to September 30, 2019 (the date of final follow-up).

Exposures: Self-reported racial and ethnic data were obtained from the National Patient Care Database. US region was determined using Centers for Disease Control and Prevention (CDC) regions from residential zip codes.

Main outcomes and measures: Incident diagnosis of dementia (9th and 10th editions of the International Classification of Diseases). Fine-Gray proportional hazards models were used to examine time to diagnosis, with age as the time scale and accounting for competing risk of death.

Results: Among the 1 869 090 study participants (mean age, 69.4 [SD, 7.9] years; 42 870 women [2%]; 6865 American Indian or Alaska Native [0.4%], 9391 Asian [0.5%], 176 795 Black [9.5%], 20 663 Hispanic [1.0%], and 1 655 376 White [88.6%]), 13% received a diagnosis of dementia over a mean follow-up of 10.1 years. Age-adjusted incidence of dementia per 1000 person-years was 14.2 (95% CI, 13.3-15.1) for American Indian or Alaska Native participants, 12.4 (95% CI, 11.7-13.1) for Asian participants, 19.4 (95% CI, 19.2-19.6) for Black participants, 20.7 (95% CI, 20.1-21.3) for Hispanic participants, and 11.5 (95% CI, 11.4-11.6) for White participants. Compared with White participants, the fully adjusted hazard ratios were 1.05 (95% CI, 0.98-1.13) for American Indian or Alaska Native participants, 1.20 (95% CI, 1.13-1.28) for Asian participants, 1.54 (95% CI, 1.51-1.57) for Black participants, and 1.92 (95% CI, 1.82-2.02) for Hispanic participants. Across most US regions, age-adjusted dementia incidence rates were highest for Black and Hispanic participants, with rates similar among American Indian or Alaska Native, Asian, and White participants.

Conclusions and relevance: Among older adults who received care at VHA medical centers, there were significant differences in dementia incidence based on race and ethnicity. Further research is needed to understand the mechanisms responsible for these differences.

Figure 1.. Cohort Development in a Study of the Association of Race and Ethnicity With Incidence of Dementia

Patients were required to have at least 1 visit during the 2-year period before their random selection date (baseline) and at least 1 follow-up visit.

Figure 2.. Cumulative Incidence of Dementia by Racial and Ethnic Group^a

^aAge is used as the timescale to indicate age at dementia diagnosis, and death is treated as a competing risk. Participants contributed follow-up data either until the age they died or developed dementia (whichever came first); patients who did not develop dementia or die continued to contribute to follow-up data until the age of their last medical encounter date. Dementia is defined using a comprehensive list of International Classification of Diseases, Ninth Revision (ICD-9) and ICD-10 codes recommended by the Veterans Health Administration Dementia Steering Committee. ^bThe table shows participant numbers at 0, 5, 10, and 15 years. The curves as plotted with competing risk models do not permit the creation of a more typical table of participants at risk. See eTable 1 in the Supplement for cumulative incidence of dementia with associated 95% CIs.

Figure 3.. Dementia Incidence Rate by Race and Ethnicity and Region

The area of the circles corresponds to the actual value of the rate presented in the circle for each racial and ethnic group. Dementia is defined using a comprehensive list of International Classification of Diseases, Ninth Revision (ICD-9) and ICD-10 codes recommended by the Veterans Health Administration Dementia Steering Committee. Of the more than 1.8 million Veterans Health Administration patients, who were a mean (SD) age of 69.4 (7.9) years and were followed up for a mean of 10.1 years (median, 10.3; range 0.7-17.9 years), 13% developed dementia. See eTable 2 in the Supplement for within-region statistical comparisons in age-adjusted dementia incidence rate per 1000 person-years by race and ethnicity, and interaction of race and ethnicity and region. Region A: Connecticut, Maine, Massachusetts, New Hampshire, New York, Rhode Island, Vermont Region B: Delaware, District of Columbia, Maryland, New Jersey, Pennsylvania, Virginia, West Virginia Region C: Georgia, Florida, North Carolina, South Carolina Region D: Alabama, Kentucky, Mississippi, Tennessee Region E: Illinois, Indiana, Michigan, Minnesota, Ohio, Wisconsin Region F: Arkansas, Louisiana, New Mexico, Oklahoma, Texas Region G: Iowa, Kansas, Missouri, Nebraska Region H: Colorado, Montana, North Dakota, South Dakota, Utah, Wyoming Region I: Arizona, California, Hawaii, Nevada Region J: Alaska, Idaho, Oregon, Washington