The research points out that smoking may cause the risk of ablepsia, brain injury in old age, Alzheimer's disease and other kinds of dementia among old people.
Ms Martin's dementia interferes with her insight and it may be considered acceptable to override her autonomy by reference to the principle of non-maleficence - the requirement to prevent harm.
A study in the current issue of the journal Neurology examined 911 nonagenarian Americans and found that 45 percent of the women had dementia, compared with 25 percent of the men.