Dr Lawrence Whalley of the University of Aberdeen, who led the research, said the explanation could be that smoking causes oxidative stress - cumulative damage caused by molecules called "free radicals" - to organs including the brain.

BBC: NEWS | Health | Smoking 'is bad for your brain'

Olive oil is also a rich source of potent antioxidants called polyphenols, which may help slow the progression of atherosclerosis (narrowing of the arteries because of cholesterol and inflammatory cell accumulation) by decreasing the susceptibility of bad cholesterol to oxidative damage and stress.

CNN: How heart-healthy is olive oil?

Moreover, the widespread occurrence of nitrotyrosine in neurons suggests that oxidative damage is not restricted to long-lived polymers such as NFTs, but instead reflects a generalized oxidative stress that is important in disease pathogenesis.

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