according to an update of the Lancet Commission on Dementia Prevention, Intervention, and Care.
The original report, published in 2017, identified nine modifiable risk factors that were estimated to be responsible for one-third of dementia cases. The commission has now added three new modifiable risk factors to the list.
“We reconvened the 2017 Lancet Commission on Dementia Prevention, Intervention, and Care to identify the evidence for advances likely to have the greatest impact since our 2017 paper,” the authors wrote.
The 2020 report was presented at the virtual annual meeting of the Alzheimer’s Association International Conference (AAIC) 2020 and also was published online July 30 in the Lancet.
Alcohol, TBI, air pollution
The three new risk factors that have been added in the latest update are excessive alcohol intake, traumatic brain injury (TBI), and air pollution. The original nine risk factors were not completing secondary education; hypertension; obesity; hearing loss; smoking; depression; physical inactivity; social isolation; and diabetes. Together, these 12 risk factors are estimated to account for 40% of the world’s dementia cases.
“We knew in 2017 when we published our first report with the nine risk factors that they would only be part of the story and that several other factors would likely be involved,” said lead author, professor, University College London (England). “We now have more published data giving enough evidence” to justify adding the three new factors to the list, she said.
The report includes the following nine recommendations for policymakers and individuals to prevent risk for dementia in the general population:
- Aim to maintain systolic blood pressure of 130 mm Hg or less in midlife from around age 40 years.
- Encourage use of hearing aids for hearing loss, and reduce hearing loss by protecting ears from high noise levels.
- Reduce exposure to air pollution and second-hand tobacco smoke.
- Prevent , particularly by targeting high-risk occupations and transport.
- Prevent alcohol misuse and limit drinking to less than 21 units per week.
- Stop smoking and support individuals to stop smoking, which the authors stress is beneficial at any age.
- Provide all children with primary and secondary education.
- Lead an active life into midlife and possibly later life.
- Reduce obesity and diabetes.
The report also summarizes the evidence supporting the three new risk factors for dementia.
TBI is usually caused by car, motorcycle, and bicycle injuries; military exposures; boxing, horse riding, and other recreational sports; firearms; and falls. The report notes that a single severe TBI is associated in humans and in mouse models with widespread hyperphosphorylated tau pathology. It also cites several nationwide studies that show that TBI is linked with a significantly increased risk for long-term dementia.
“We are not advising against partaking in sports, as playing sports is healthy. But we are urging people to take precautions to protect themselves properly,” Dr. Livingston said.
For excessive alcohol consumption, the report states that an “increasing body of evidence is emerging on alcohol’s complex relationship with cognition and dementia outcomes from a variety of sources including detailed cohorts and large-scale record-based studies.” One French study, which included more than 31 million individuals admitted to the hospital, showed that alcohol use disorders were associated with a threefold increased dementia risk. However, other studies have suggested that moderate drinking may be protective.
“We are not saying it is bad to drink, but we are saying it is bad to drink more than 21 units a week,” Dr. Livingston noted.
On air pollution, the report notes that in animal studies, airborne particulate pollutants have been found to accelerate neurodegenerative processes. Also, high nitrogen dioxide concentrations, fine ambient particulate matter from traffic exhaust, and residential wood burning have been shown in past research to be associated with increased dementia incidence.
“While we need international policy on reducing air pollution, individuals can take some action to reduce their risk,” Dr. Livingston said. For example, she suggested avoiding walking right next to busy roads and instead walking “a few streets back if possible.”