Introduction: Estimates of US adults with dementia differ widely and don't distinguish adults living in the community. Methods: Behavioral Risk Factor Surveillance System data from 120485 households in 21 states that used a cognitive decline module in 2011 were used. Data for both respondents and other adults with subjective cognitive decline (SCD) were included through proxy responses. Using responses to questions about the receipt of informal care for their SCD and diagnosed dementia, estimates were made for each state. Results: Overall, 2.9% (range: 1.5% in Tennessee to 5.3% in Arkansas) of all noninstitutionalized adults in these states received informal care for their SCD and 0.9% (range: 0.5% in Tennessee to 2.0% in Arkansas) were estimated to have dementia. Limiting results to respondents reduced estimates significantly. Discussion: Combined results for respondents and nonrespondents from a representative telephone survey provide varying estimates of SCD-related measures across states, highlighting the need for state-specific estimates.