It Is important to refute Susan Greenfield's statement that "Parkinson's disease is a disorder of the elderly like Alzheimer's..." ("When the brain goes down the drain", Review, 24 November). My wife was diagnosed with Parkinson's when she was 42 and research shows that as many as one in 20 "sufferers" reveals evidence of the disease before the age of 40. There are several diagnosed teenagers and a child of six is thought to have it. Sadly, the misconception that this disease is confined to the elderly has a negative effect on fundraising. Brilliant medical research is under way (with a breakthrough possible in the foreseeable future), but it is in grave danger of failing through lack of finance.