Jessica Faul Health and Retirement Study

1. Approaches to Assessing and Correcting for Bias in Distributions of Cognitive Ability due to Biased Non-Response – Part 2Using Medicare Claims March 23, 2009 Jessica Faul Health and Retirement Study

2. Medicare Claims • Medicare claims can supplement survey data by providing an external source of disease diagnosis • Strengths: • Virtually all persons age 65 over are covered • Linkage provides information both before / after interview period • Data on non-responders

3. Medicare Claims • Insidious nature of AD/dementia may affect agreement • Highly imperfect as passive case ascertainment • Claims are for billing (up coding / over-diagnosis for charging purposes) • Managed care (HMO) claims not included • Under-diagnosis of those not seeking care

4. Medicare Claims & ADAMS • To use to correct for selection bias, need good correlation not substitute for direct observation of person • Paper by Taylor et al. evaluated the accuracy of using Medicare claims to identify AD & dementia • Compared Medicare claims (1993-2005) to clinical dementia assessments (2001-2003) for the ADAMS study (n=758)

5. Accuracy of Medicare claims-based dementia diagnosis comparison to ADAMS (weighted) • D. Taylor, T. Ostbye, K. Langa, D. Weir, B. Plassman The accuracy of Medicare claims as an epidemiological tool: the case of dementia”, forthcoming, Journal of Alzheimer Disease

6. Medicare Claims & HRS • Claims for all available years (1991-2005) • ICD-9 diagnosis codes for AD and other dementias (331, 290 ,294, 797) • Dementia diagnosis by response category in 2006 • interviewed (self/proxy), non-response, dead

7. Medicare Linkage • Combination of permission and matching process • Higher % consent among older cohorts

8. Medicare Managed Care • Utilization files contain mostly fee-for-service (FFS) claims • Hospice services excepted • Enrollment peaked in 1999 with 17.9% • Remove persons or person-months from cohort • Identified using denominator file • ~15% in HMO in HRS, higher among older cohorts

9. Percent with claims-based dementia diagnosis, by HRS 2006 response type and birth cohort

10. Percent with claims-based dementia diagnosis, by HRS 2006 response type and birth cohort – Proxy

11. Does it matter? • HRS 2006 Respondents • 86% of Rs 70+ gave consent for Medicare linkage and matched denominator file • Of these, 70% continually FFS • N=5092 • 7.8% with dementia Dx (unweighted)

12. Does it matter? • Loss of non-responders • Add 20% to the sample of respondents • 13.1% with dementia Dx → Prevalence of 8.8% (1 pt increase) • Omission of proxy cases • 7.6% of the sample IW by proxy in 2006 • 44.2% with dementia Dx → Prevalence of 4.8% (3 pt decrease)

13. Bias from Medicare Consent? • Potential bias if sample giving consent to link to Medicare records not representative • Weights would have to account for differential consent among groups • However, no differences between 2006 sample 70+ and Rs with Medicare linkage on age, education, self-rated health, health conditions, ADLs / IADLs • African -Americans and Hispanics less likely to consent

14. Claims can be used to correct what is observed in the survey • Modest differences in claims Dx between respondents and non-respondents when proxies are included • Higher % proxy and higher prevalence of dementia among older cohorts • High response rates in HRS (over 80% of survivors) → very modest correction

15. Conclusions • Surveys have their work cut out for them but there are solutions to the problem of representing the cognitively impaired • Neurologists and epidemiologists also have their work to do reaching consensus on what to measure, how to measure it, and how to measure it with reasonable accuracy on a survey

16. THANK YOU http://hrsonline.isr.umich.edu/