Are older adults using ChatGPT for medical advice? Results from a cross-sectional survey study

General-purpose large language models (LLMs) like ChatGPT are increasingly used for medical advice despite lacking medical training and frequently producing incorrect or unsafe output. Older adults' health information-seeking behaviors using LLMs remain poorly characterized. We conducted a cross-sectional survey of 574 US adults aged 50+ recruited via Prolific, balanced by sex and race. Participants reported health information sources, ChatGPT and PubMed use, demographics, and health literacy. Most participants (92%) searched online for health information. All had heard of ChatGPT, and 63% used it for medical information, compared to 44% who had heard of PubMed and 39% who used it. Those with inadequate health literacy had higher odds of ChatGPT use for medical advice (AOR 2.36, 95% CI 1.30-4.52) versus those with adequate health literacy. In conclusion, with more than half of older adults using LLMs for medical advice, the development of safer, purpose-trained medical LLMs is warranted.