http://www.bbc.com/news/uk-scotland-glasgow-west-35342607
They said he was "a keen and active walker and enjoys country and forestry trails", adding it may be "possible that he may have tried to walk home to Balfron".
Police said that the last confirmed sighting of Mr Miller had been at the BP Garage in Main Street, Jamestown, Alexandria, at about 00:20 hours on Thursday 7 January.
He had spent most of the evening in Fenton's Bar, which is located on the same road.
Earlier on 6 January, Mr Miller was spotted on CCTV within Tesco in Milngavie at about 13:15.
During the new conference, Ch Insp Graeme MacDiarmid revealed that officers had received two further unconfirmed sightings of Mr Miller in the Bonhill and Balloch areas.
The Balloch sighting was on the evening of 8 January in the Balloch Road area.