Half of women will develop dementia, Parkinson's disease or have a stroke in their lifetime, new research suggests.
About a third of men aged 45 and one in two women of the same age are likely to go on to be diagnosed with one of the conditions, according to a study of more than 12,000 people.
The researchers, from the University Medical Centre Rotterdam, in the Netherlands, said preventative measures could "substantially" reduce the burden of the illnesses.
The findings have been published in the Journal of Neurology, Neurosurgery, and Psychiatry.
The health of 12,102 people was monitored between 1990 and 2016, with all participants initially under the age of 45.
During this period 1,489 were diagnosed with dementia and 263 with parkinsonism, while 1,285 had a stroke.
The overall risk of a 45-year-old later developing one of the three conditions was 48 per cent for women and 36 per cent for men, the researchers said.
Dementia was of greatest concern for women, who at 45 years old had a 25.9 per cent risk of going on to develop the condition, compared with 13.7 per cent for men.
Dr Carol Routledge, director of research at Alzheimer's Research UK, said: "This large study underscores the enormous impact that neurological illnesses have across society and how women are disproportionately affected, particularly when it comes to dementia."
Those diagnosed with one of the three conditions were found to have a higher prevalence of high blood pressure, abnormal heart rhythm, high cholesterol and Type 2 diabetes at the start of the monitoring period.
"These findings strengthen the call for prioritising the focus on preventative interventions at population level which could substantially reduce the burden of common neurological diseases in the ageing population," the authors said.
They estimate that if onset of dementia, parkinsonism and stroke was delayed by one to three years, the remaining risk of developing the conditions could be cut by 20 per cent among 45 year olds and more than 50 per cent in those older than 85.
Dr Routledge said it was "crucial" that efforts to find a drug which can delay the onset of dementia symptoms were increased.
