By Michelle Roberts
Health reporter, BBC News
Statins are used by nearly 2m UK people to prevent heart attacks and stroke by lowering harmful blood cholesterol.
Statins are used to lower cholesterol
But US scientists are concerned after a small study found people with low cholesterol upped their risk of developing Parkinson's disease.
Now the University of North Carolina team is to study 16,000 people to see if the link is real and causal.
If it is, a surge in Parkinson's cases is imminent they say. But experts argue statins may in fact protect against it.
Indeed, Dr Xuemei Huang's group discovered themselves that people on statins were less likely to have Parkinson's disease.
Their study, published in Movement Disorders, included 124 patients with Parkinson's and 112 of the patients' partners, who acted as controls.
They found that patients with lower "bad" LDL cholesterol levels were more than three times more likely to have Parkinson's than those with higher LDL cholesterol levels.
Paradoxically, those on statins were less likely to have the condition.
Dr Huang says this could be because those who develop Parkinson's have had low LDL cholesterol all their life and so have never needed to take statins.
She told Chemistry & Industry that past studies linking Parkinson's with a gene (apoE2) associated with lower cholesterol support her theory that low LDL is the culprit.
Because statins lower LDL cholesterol, the concern is they may trigger Parkinson's.
Dr Huang said: "I'm definitely concerned which is why I'm conducting a prospective study of 16,000 people."
But Dr David Dexter, senior lecturer in neuropharmacology at Imperial College, London, said: "With the evidence we have at the moment, I would say there is not much cause for concern that statin use may cause Parkinson's disease."
He said previous studies had demonstrated that statins can increase brain dopamine concentration - the chemical transmitter deficient in Parkinson's - and that statins protect nerve cells.
"Also one of the secondary symptoms some patients with Parkinson's experience is dementia, similar to Alzheimer's disease, which may result from vascular changes in the brain. Statins would be expected to protect the brain against such vascular changes," he explained.
Professor Peter Weissberg, of the British Heart Foundation, said he was concerned that any suggestion of a link between statins and Parkinson's disease would unnecessarily scare the millions of people benefiting from statins in the UK.
"There is no evidence to suggest that statins cause Parkinson's disease. There is, however, overwhelming evidence that statins save lives by preventing heart attacks and strokes.
"Nobody should stop taking statins on the basis of this report. If they do, they will be putting themselves at increased risk of heart attack or stroke," he warned.
Dr Huang agreed that the medical value of statins far exceeded any possible additional risk of Parkinson's.
Professor Yoav Ben-Shlomo, professor of clinical epidemiology at Bristol University, said patients had a right to know the risks of any medication they were taking.
He said a prospective study - tracking the lifestyle of people before Parkinson's develops - should help provide more answers.
Dr Kieran Breen, of the Parkinson's Disease Society, said: "We hope that the proposed study will shed further light on this.
"Some people have found a relationship and others have not. The evidence is inconclusive. The jury is very much still out on this."
He stressed that the most likely cause was a mixture of genetic and environmental factors.