Rural-urban differences in diagnostic incidence and prevalence of Alzheimer's disease and related dementias

Abstract

Introduction: Understanding rural-urban variation in the diagnostic incidence and prevalence of Alzheimer's disease and related dementias (ADRD) will inform policies to improve timely diagnosis and access to supportive services for older adults in rural communities.

Methods: Using 2008 to 2015 national claims data for fee-for-service Medicare beneficiaries (roughly 170 million person-years), we computed unadjusted and adjusted diagnostic incidence and prevalence estimates for ADRD in metropolitan, micropolitan, and rural counties, and examined differences in survival rates.

Results: Risk-adjusted ADRD diagnostic incidence was higher in rural versus metropolitan counties despite lower prevalence. Among beneficiaries diagnosed with ADRD in 2008, metropolitan county residents experienced longer survival compared to residents in rural and micropolitan counties.

Discussion: These data suggest that older adults in rural communities may be underdiagnosed with ADRD, and/or diagnosed at later stages of dementia. Further work is needed to develop strategies to reduce this disparity.

Keywords: ADRD; diagnostic incidence; diagnostic prevalence; rural-urban disparity.

FIGURE A1

Alzheimer’s disease and related dimentias (ADRD) incidence ratios among Medicare fee-for-service (FFS) beneficiaries

FIGURE A2

Alzheimer’s disease and related dimentias (ADRD) prevalence ratios among Medicare fee-for-service (FFS) beneficiaries

FIGURE A3

Diagnostic incidence and prevalence of Alzheimer’s disease and related dimentias (ADRD) among Medicare fee-for-service (FFS) beneficiaries in urban and rural counties in 2015 across different regions of the US. (A) Percent of Medicare FFS beneficiaries newly diagnosed with ADRD in 2015. (B) Percent of Medicare FFS beneficiaries that started 2015 with an ADRD diagnosis

FIGURE A4

Alzheimer’s disease and related dimentias (ADRD) prevalence ratios among deceased Medicare fee-for-service (FFS) beneficiaries

FIGURE A5

Diagnostic incidence and prevalence of Alzheimer’s disease and related dimentias (ADRD) among Medicare fee-for-service (FFS) beneficiaries in 2015 with different levels of risk adjustment. (A) Percent of Medicare FFS beneficiaries newly diagnosed with ADRD in 2015. (B) Percent of Medicare FFS beneficiaries that started 2015 with an ADRD diagnosis

FIGURE 1

Diagnostic incidence and prevalence of Alzheimer’s disease and related dementias (ADRD) in urban and rural counties in the US from 2008 to 2015. (A) ADRD diagnostic incidence. (B) ADRD diagnostic prevalence. Adjusted measures and the 95% confidence intervals are estimated separately for each year using two steps. First, we estimate a multinomial logit regression of ADRD diagnosis onto rurality of beneficiary’s residential county, beneficiary’s demographic, clinical and residential zip code characteristics (listed in Table 1). Second, we estimate the marginal effects of rurality. Abbreviations: Metro, metropolitan counties; Micro, micropolitan counties; Rural, rural counties

FIGURE 2

Proportion of deceased Medicare beneficiaries with Alzheimer’s disease and related dementias (ADRD), 2008 to 2015. Adjusted measures and the 95% confidence intervals are estimated separately for each year using two steps. First, we estimate a logit regression of ADRD diagnosis onto rurality of beneficiary’s residential county, beneficiary’s demographic, clinical and residential zip code characteristics (listed in Table 2). Second, we estimate the marginal effects of rurality. Abbreviations: Metro, metropolitan counties; Micro, micropolitan counties; Rural, rural counties

FIGURE 3

Adjusted survival functions among beneficiaries newly diagnosed with Alzheimer’s disease and related dementias (ADRD) in 2008. Survival functions are plotted based on Cox regression onto rurality of beneficiary’s residential county, beneficiary’s demographic, clinical and residential zip code characteristics (listed in Table 1). Detailed results of the Cox regression are presented in Appendix Table 5. Second, we estimate the marginal effects of rurality. Lines for rural (green) and micropolitan (red) counties are almost identical and overlapping in this figure. Abbreviations: Metro, metropolitan counties; Micro, micropolitan counties; Rural, rural counties