That’s according to researchers from University College London (UCL) in the United Kingdom who analyzed 27 papers about dementia that had data collected over more than 70 years. They calculated what share of dementia cases were due to different risk factors. Their findings were recently published in the Lancet Public Health.
Top risk factors for dementia over the years have been hypertension, obesity, diabetes, education, and smoking, according to a news release on the findings. But the prevalence of risk factors has changed over the decades.
Researchers said smoking and education have become less important risk factors because of “population-level interventions,” such as stop-smoking campaigns and compulsory public education. On the other hand, obesity and diabetes rates have increased and become bigger risk factors.
Hypertension remains the greatest risk factor, even though doctors and public health groups are putting more emphasis on managing the condition, the study said.
“Cardiovascular risk factors may have contributed more to dementia risk over time, so these deserve more targeted action for future dementia prevention efforts,” said Naaheed Mukadam, PhD, an associate professor at UCL and the lead author of the study.
Eliminating modifiable risk factors could theoretically prevent 40% of dementia cases, the release said.
The CDC says that an estimated 5.8 million people in the United States have Alzheimer’s disease and related dementias, including 5.6 million people ages 65 and older and about 200,000 under age 65. The UCL release said an estimated 944,000 in the U.K. have dementia.
A version of this article first appeared on WebMD.com.