A Suffolk Police spokesperson said: “The man is currently being questioned at Martlesham police investigation centre, where he remains.
“Specialist officers are supporting Anita’s family and keeping them updated on the investigation.
“Anyone with any information that may assist with this inquiry is asked to contact the major investigation team.”
Ms Rose had left her home at about 05:00 BST on 24 July and was discovered unconscious by a member of the public at 06:25 BST near the Anglian Water sewage works and railway line off Rectory Lane in Brantham.
Villagers reported seeing an increased police presence in the area on Thursday, including a helicopter and dog units.
