Italian researchers looked at the coffee drinking and smoking habits of 166 people with blepharospasm.
Sufferers have uncontrollable twitching of the eyelid which, in extreme cases, stops them being able to see.
It usually affects people aged between 50 and 70 and someone with blepharospasm may be unable to prevent their eyes from clamping shut, so that, at times, they are effectively “blind”.
The first symptoms may include eye irritation and discomfort, sensitivity to light and increased blinking.
Professor Giovanni Defazio and colleagues from the Department of Neurological and Psychiatric Sciences University of Bari in Italy said a previous study had suggested smoking had a protective effect on the condition.
They compared smoking and drinking habits in patients with the condition with patients with hemifacial spasm (a similar muscle spasm that usually begins in the eyelid muscles but then spreads to involve other muscles of the face) and people who were relatives of patients.
In the current study there was no significant association found with smoking but those who drank coffee were less likely to develop the condition.
The effect was proportional to the amount of coffee drunk and the age of onset of the spasm was also found to be greater in patients who drank more coffee – 1.7 years for each additional cup per day.
Can anyone name the enormous set of confounders available for this study?