The wife of 65-year-old Ian Collett, missing since Saturday, has made a public plea for people to watch out for him as he enters his fourth night alone.

The grandfather has dementia, but is very fit and has covered a lot of ground since he left his Canning Vale home on Saturday, with sightings confirmed in Armadale, Byford and Jarrahdale.

Deborah Collett, wife of missing man Ian Collett. Credit:9 News Perth.

It is believed he might be headed towards Albany, where he has family, or Mount Barker, where he once lived.

His wife, Deborah Collett, told 9 News Perth her husband was wearing a medic alert bracelet with his name, the word ‘dementia’ and her mobile number.