The search for missing Auckland woman Patricia Wearn continues this morning, almost a week after she was last seen, as police say she is unlikely to have survived this long.

The 73-year-old, who has Alzheimer's, hasn't been seen since she left her home on Caversham Dr, Torbay, for a walk on Monday.

Searchers are this morning scouring several bush areas in Torbary reserves, in further attempts to locate her, as well as searching homes and houses in the area.

Hundreds of people from Police, LandSAR, Navy, Airforce and the Fire Service have been involved in a large-scale operation to find her, but no sign has been found.

Police have consulted extensively with medical experts who are trained in survival.

"Sadly we have now well passed the survivability expectations for Mrs Wearn, and though we are continuing the search today, tomorrow we will be reviewing our search options," Inspector Sunny Patel said in a statement this morning.

"We are asking anyone who has been away on holiday and lives in the Torbay area to please search your property."

Anyone who has not been able to search their properties themselves is asked to contact the North Shore Police on 09 477 5000.