Using a unique nationally-representative sample from the HRS- Medicare claims linked data, we found that approximately 40% of older adults ≥ 67 years old with HF are cognitively impaired, with 15% demonstrating moderate/severe impairment consistent with dementia. HF was independently associated with an increased risk for cognitive impairment (CI). Our prevalence estimates of CI fell within the range (25–46%) most commonly reported by prior studies, but the prevalence of moderate/severe CI consistent with dementia was lower than previously reported. We also found that HFhas a significant, independent association with dementia after adjustment for important sociodemographic and clinical predictors.
Comparing prevalence estimates across studies is difficult because of differences in patient samples (in HF type and study setting) and the large variability in cognitive tests utilized across studies. Our study’s strengths are its use of a broad case-mix of HF cases by use of an algorithm which likely captures the mild-severe stages of HF, the presence of a comparison groups within the cohort, and its use of standardized cognitive measures that are validated from clinically diagnosed cognitively impaired cases from ADAMS, an epidemiologic substudy of dementia in the HRS(26
). The TICS-m and informant assessment of cognitive performance discriminate well between demented and mild cognitively impaired cases (22
Several limitations of our study warrant mention. First, both self-report and Medicare claims data have limited validity as accurate measurements of HF. Multiple factors can influence a patient’s awareness of a heart condition such as illness severity, including socioeconomic background, race, patient health awareness gained through encounters with healthcare providers and effective self-management skills. The validity of Medicare administrative data is also highly dependent on many factors: ICD-9 coding practices, organizational culture, coder experience, and the type of administrative file utilized(28
). For these reasons, our prevalence estimates may be an over- or underestimate of HF cases in the population. Using HRS-Medicare linked data in prior work, self-report prevalence of HF at 5% is an undercount; claims-based prevalence at 16%, an over count (21
). Thus, our algorithm which combines self- and proxy-report of a heart problem with ≥ 1 Medicare diagnostic HF claim is likely more accurate than use of self- or proxy-report or claims data alone in this data source.
Second, medical records were not available to further adjudicate cases, ascertain HF severity, or determine the use of medications that might affect cognition. Third, approximately 11% of the HRS respondents did not consent to the linkage of their survey data to Medicare claims. These factors may introduce selection bias since the population enrolled in managed care programs differs from those with traditional Medicare fee-for-service plans with respect to health and socioeconomic status (29
). Fourth, the cognitive measures utilized in our study may insufficiently probe the cognitive domains most commonly affected in HF patients leading to inaccuracies in our findings. Our estimates of moderate/severe impairment are lower than prior epidemiological reports likely due to the exclusion of nursing home residents.(30
) Nonetheless, this work provides among the first estimates of global cognitive function in a nationally representative sample.
CI commonly co-occurs with HF in older adults, yet assessing cognition is not routinely incorporated into traditional HF disease management models of care. Awareness of cognitive status by healthcare providers, in particular HF care providers, is important for setting expectations for patient participation in a HF treatment plan and achieving optimal care. We found an independent association of HF with the presence of moderate/severe CI-a cognitive performance level most consistent with dementia. CI is an under-recognized comorbid condition in community-dwelling older adults with HF which will have important effects on prognosis, physical function, quality of life, healthcare utilization, and mortality.