The Comprehensive Process Model of Group Engagement posits that personal factors (e.g., cognitive function), stimulus factors (e.g., group activity content, group size) and environmental factors (e.g., light, noise) impact the response to group activities. This paper reports the impact of environmental and group characteristics on engagement, mood, and sleepiness of persons with dementia attending group activities.. To read the full article, log in using your MPFT NHS OpenAthens details.