Cathryn Holdsworth was last seen at Calderdale Royal Hospital on Friday, September 8, and is believed to have travelled by bus back towards Mixenden that evening.
But there have been no further confirmed sightings since then and searches by specialist teams have failed to track her down.
West Yorkshire Police today made a renewed plea for information, saying she may have travelled anywhere across the UK since she vanished.
Inspector Toby Facey, who is leading the investigation said: “We have issued numerous appeals over the last weeks in our efforts to find Cathryn, however we have not been able to locate her.
“We have been using a number of specialist resources to try and understand where Cathryn may be, including specialist police search teams, Calder Valley Search and Rescue, and other partnership resources.
“I would once again appeal to anyone who may have any information about Cathryn, or who may have seen her in the last six weeks to come forward.
“Whilst we know Cathryn has previous links to Blackpool in Lancashire and Cornwall, we now believe it is possible she may have travelled anywhere across the UK.
"I would also directly appeal to any hotels or guest houses to think back to if someone matching Cathryn’s description has stayed there in these past six weeks."
Cathryn was reported missing by her neighbours on Tuesday, September 16.
She is around 5ft 2in and of medium build, with very short speckled grey hair and dark glasses.
Cathryn is known to use a walking frame to assist her, but does not use it all the time.
Officers are very concerned for Cathryn’s welfare as she is considered to be vulnerable.
Insp Facey said: “Our priority is Cathryn’s welfare, and making sure she is OK.
"Anyone who has any information that can assist us should feel confident in coming forward to the police, no matter how small or insignificant the information may seem in isolation.
"If you have seen Cathryn, make that call.”
Anyone with information on her recent or current whereabouts is urged to call West Yorkshire Police via 101, quoting 13170435010.