Ultra-processed foods are typically high in added sugar, fat and salt, and lack protein and fibre.

Other examples include some packaged salty and sugary snacks, canned baked beans, packaged bread and flavoured cereals.

The researchers stressed that their study, carried out in the US, could not prove that ultra-processed foods caused the health problems, but it showed an association.

Study leader Dr William Taylor Kimberly, of Massachusetts General Hospital in Boston, said: “While a healthy diet is important in maintaining brain health among older adults, the most important dietary choices for your brain remain unclear.

“We found that increased consumption of ultra-processed foods was associated with a higher risk of both stroke and cognitive impairment, and the association between ultra-processed foods and stroke was greater among Black participants.”

Ultra-processed foods have previously been linked to greater risk of heart problems including high blood pressure, cardiovascular disease, and heart attacks.

Dr Kimberley added: “Our findings show that the degree of food processing plays an important role in overall brain health.

“More research is needed to confirm these results and to better understand which food or processing components contribute most to these effects.”

The findings were published online in Neurology, the medical journal of the American Academy of Neurology.