From the article:
The research, carried out by Dr Karolina Wartolowska, a clinical research fellow at the Centre for Prevention of Stroke and Dementia, University of Oxford, UK, looked for damage in the brain called “white matter hyperintensities” (WMH). These show up on MRI brain scans as brighter regions and they indicate damage to the small blood vessels in the brain that increases with age and blood pressure. WMH are associated with an increased risk of stroke, dementia, physical disabilities, depression and a decline in thinking abilities.
Dr Wartolowska said: “Not all people develop these changes as they age, but they are present in more than 50% of patients over the age of 65 and most people over the age of 80 even without high blood pressure, but it is more likely to develop with higher blood pressure and more likely to become severe.”
[…]
The researchers found that a higher load of WMH was strongly associated with current systolic blood pressure, but the strongest association was for past diastolic blood pressure, particularly when under the age of 50. Any increase in blood pressure, even below the usual treatment threshold of 140 mmHg for systolic and below 90 mmHg for diastolic, was linked to increased WMH, especially when people were taking medication to treat high blood pressure.*