This 2010 document details real research into the subject and has come up with a series of design recommendations that include
the importance of relating activity to space, the need for safe spaces to reduce anxiety and the role of transitional spaces. A very inciteful document that explains how this complex disability relates to design.
This 2013 document was published to raise awareness, explain why particular design features are needed, and to give basic guidance on the most important ones. If housing is designed well it can extend the amount of time a person with dementia can remain at home. It can also reduce the sort of adverse incidents that lead to hospital admissions.
The links below offer practical guidance on how to improve home and learning environments to be more accessible to Autistic people. The guidance offered is concise and informative and offers some real insight into the perception of environments by Autistic people at various levels on the Autistic spectrum and how Autism effects behaviour and interaction.