Using over 25 years’ worth of data from more than 12,000 subjects, a team from the Erasmus University Medical Center in Rotterdam, the Netherlands, has concluded that the lifetime risk of suffering a stroke or developing dementia or Parkinson’s disease is 48 percent in women and 36 percent in men.

Their new study, published in the Journal of Neurology, Neurosurgery & Psychiatry, was undertaken with the hope that an accurate and straightforward quantification of the alarming prevalence of neurological disorders will bolster the call for increased research into preventative treatments.

“Recent estimates indicate that the global costs-of-illness for these diseases sum up to more than 2 percent of the annual world gross domestic product," the authors wrote. "This socioeconomic burden is expected to grow steeply with the aging of populations and continuing increases in life-expectancy worldwide. 

“Yet, these common neurological diseases remain understudied in terms of prevention at the population level and underfunded compared with other common diseases such as cancer and heart disease, which likely reflects skewed societal perceptions of lifetime risk.”

Lead investigator Dr M Arfan Ikram and his colleagues note that past investigations have provided muddled estimates of prevalence because many don’t account for the fact these conditions often occur together – they share many risk factors, such as high blood pressure and cholesterol – or fail to analyze men and women separately (lifetime risk is different due to women’s longer life expectancy).

To provide a stronger portrait of disease likelihood, Ikram’s group turned to the dataset from the famous Rotterdam Study – an assessment of age-related diseases that followed nearly 15,000 residents, aged 45 and above, of a Rotterdam suburb for 26 years. Participants who had a history of any of the three diseases at the study onset were excluded, leaving 12,102 individuals.

The team’s analysis of health records from the cohort showed the risks listed above and many more jarring statistics. When assessing the diseases individually, they found that dementia was more common in women (26 percent risk) than men (14 percent risk). For stroke, men and women had a similar lifetime risk (19 percent each after 45 years of age), but men were more likely to have a stroke at younger ages. Various Parkinson's-like disorders were rare and showed similar rates across sexes.

Participants who were diagnosed with one of these diseases during the study period were more likely to have high blood pressure, irregular heartbeat, high blood cholesterol levels, and type 2 diabetes compared to those who were not.

Naturally, there are some inherent limitations to studies with this type of design. First off, the population is a fairly uniform group from one area of the world, meaning that the risk findings may not apply to people from other, non-European ethnic groups. Second, the data does not account for the severity of the conditions, and does not detail the economic and emotional burden of these diseases in the period prior to the onset of the first clinically documented symptom.

Until we know more about the early disease processes that lead to stroke, dementia, and Parkinson's – and before we can develop lifestyle or pharmacological interventions that effectively stop them – sticking to all the obvious health advice is your best bet, according to Dr Carol Routledge, director of research at Alzheimer’s Research UK.

“The best current evidence suggests that eating a balanced diet, controlling our weight, staying physically active, not smoking, only drinking within the recommended limits and keeping blood pressure and cholesterol in check are all associated with better brain health into old age,” she told The Guardian.