Parkinson's disease is a degenerative neurological disorder, which becomes more common with older age. But its cause is still unclear.
The research team compared 106 patients with confirmed Parkinson's disease with 106 healthy people of the same age and sex. Both groups completed a validated questionnaire designed to clarify personality traits and behaviour.
Information was also collected on cigarette smoking, coffee and alcohol intake: previous research indicates that higher caffeine and nicotine consumption may protect against Parkinson's disease.
Patients with Parkinson's disease scored lower on sensation seeking/risk taking behaviour and higher on anxiety and depression than the healthy comparison group.
They were also less likely to have ever smoked, and when they had to have given up many years earlier. They also drank less coffee and alcohol than their healthy peers.
When the data were analysed further, the association between less tendency to sensation seeking/risk taking behaviour and higher rates of Parkinson's disease remained, irrespective of smoking, coffee and alcohol intake.
Furthermore, the disinclination to sensation seeking explained some of the apparent effect of caffeine and alcohol on Parkinson's disease.
The findings prompt the authors to suggest that there may be a neurobiological link between low sensation seeking behaviour, which might underpin the "parkinsonian personality," and the supposed protective effect of cigarette smoking and coffee consumption.
Patients with Parkinson's disease tend to spurn openly hedonistic activity while at the same time being scrupulous, socially withdrawn, inflexible, disinclined to take risks and relatively passive.
Dopamine systems in the brain may help explain the particular behavioural and personality traits in Parkinson's disease, which can precede the emergence of movement problems by several decades, say the authors.