Can be, Mary, but can be due to many other things too. It could be due to vitamin deficiency (especially vitamin B12), thyroid underaction, stress, tiredness and TBH, its something that I have done all my life and, as far as I know I dont have dementia!
If it is dementia there will be other symptoms too. The best thing is to go and see the GP who can do blood tests to see if its something like a vitamin deficiency. If its not, he might do a referral to the memory clinic.