EDITOR—Doll et al's finding that “persistent smoking does not substantially reduce the age specific onset rate of Alzheimer's disease or of dementia in general” is not surprising.1 The authors didn't compare smokers with non-smokers.

By combining lifelong non-smokers and ex-smokers in the non-continuing group they effectively stopped comparing smokers with non-smokers. To complicate the issue further they then note, “As questionnaires were sent out only every six to 12 years, the mean time before death that the relevant smoking habits had been recorded was not 10 but 15 years.” In the end this study compares a group including non-smokers and ex-smokers who may have started smoking in the previous 15 years with a group of smokers who may have stopped in the previous 15 years.

Has the BMJ fallen prey to the concerted and unrelenting efforts of health organisations determined to dictate an antismoking social policy rather than provide the honest and unbiased facts that people need to make informed personal choices? Or is the BMJ part of the team?