New evidence on smoking and dementia

A large U.S. study of over 21,000 people has added to the considerable pile of evidence linking smoking to dementia. The study - carried out by Dr Rachel Wittmer from the U.S. health organization Kaiser Permanente - found that smoking 40 or more cigarettes a day led to a 157% increase in the risk of Alzheimer's disease and a 172% increase in the risk of vascular dementia. However, there was no increase in risk in those smoking less than ten cigarettes a day and people who gave up smoking by middle age had the same level of risk as people who had never smoked.