Further Evidence that Dementia is Preventable – Plus 3 New Dementia Risk Factors

The Alzheimer’s Association International Conference (AAIC) was held a few weeks ago online. Due to  Covid, the conference was virtual. Scientific presentations continued to reiterate that there are no pharmaceuticals that slow or impact the progression of memory loss or Alzheimer’s disease. However, the evidence continues to build for the powerful impact of addressing modifiable risk factors. A number of publications have cited that up to 50% of dementia is preventable.

A 2011 Lancet publication documented that up to 50% of Alzheimer’s cases globally and in the US potentially could be prevented by modifying just 7 dementia risk factors. In 2017,  The Lancet Commission on dementia prevention, intervention, and care modelled 9 modifiable risk factors accounting for the majority of dementia cases including less education, hypertension, hearing impairment, smoking, obesity, depression, physical inactivity, diabetes and low social contact. Recent research published in Lancet in August 2020 reviews a meta-analysis that adds 3 more risk factors for dementia that have new convincing evidence.

Three More Risk Factors for Dementia

1. Excessive Alcohol Consumption

It has been known for centuries that heavy drinking is associated with brain changes, memory loss and dementia. A 5-year longitudinal study of over 31 million people who were hospitalized found that alcohol disorders were associated with increased dementia risk. This was particularly evident in early onset dementias (dementia that starts before age 65). 57% of early onset dementia in this population had alcohol use disorder in their history.

A meta-analysis of 45 studies of light to moderate drinking showed reduced dementia risk compared to not drinking. However, drinking more than 12 units of alcohol per week (1 unit=10ml or 8 g pure alcohol) reduced reaction time. Drinking more than 21 units per week and long-term abstinence were both associated with a 17% increase in dementia compared to drinking less than 14 units. Brain imaging by MRI showed degeneration of the brain in those who drank more than 14 units per week. In conclusion, light to moderate alcohol consumption does not increase dementia risk and may even be slightly protective, whereas excessive drinking significantly increases dementia risk.

2. Head Injury

Head injury, or traumatic brain injury, can range from mild concussion to severe skull fracture, often caused by car accidents, war, athletic injuries or falls. Even one single severe head injury has been, shown to worsen memory loss pathology. A study of 3 million people over 50 years of age followed for 10 years showed a 20% increase in dementia and 20% increase in Alzheimer’s from any head injury. Dementia risk increased with the number and severity of head injuries. Those with 5 or more head injuries had 280% increase in dementia risk.

Head injury also increased risk of early onset dementia. Another study of over 3 million people over 50 years of age showed the head injury increased 1-year dementia risk 350%! And risk remained elevated over 30 years with 30% increase in dementia risk over that entire period. This study showed similar results to the previous study with multiple head injuries increasing risk 280%.

A study of 29,000 older adults with concussion showed that risk of dementia doubled in the 3.9 year follow up. Those taking statins had 13% reduced risk of dementia compared to those who never took statins. This needs further research in randomized studies, but statins may reduce the inflammation and some consequences of traumatic brain injury.

Scottish former soccer players are 510% more likely than controls to get Alzheimer’s disease.

3. Air Pollution

A systematic review of 13 longitudinal studies performed through 2018 with 1-15 years follow-up found that particulate matter in the air, nitrogen dioxide, and carbon monoxide were associated with increased dementia risk. In one large study, the particulate matter levels that were associated with increased dementia were above US guidelines. Animal models suggest particulate pollutants may accelerate cardiovascular disease, amyloid deposits, and amyloid precursor protein processing. It is still possible that the higher levels of dementia may be related to other factors such as socioeconomic status and living conditions (cause and effect have not been proven). Fine particulate matter in the air may increase risk of hypertension, atherosclerosis, inflammation and stroke, which are all risks for cognitive decline and dementia. Evidence on the impact of air pollution is smaller and less convincing than the impact of air quality on cardiovascular disease, but is growing quickly as all of the articles reviewed were
published in the last 5 years.

These new data reinforce that it is never too early and never too late for memory loss and dementia prevention. Activities in early-life, mid-life and late-life influence memory loss pathology and neurology.

Addressing risk factors is important across the life course. Now additional focus is placed on reducing exposure to air pollution and second-hand tobacco smoke, preventing traumatic brain injury and limiting alcohol use (exceeding 14 units weekly).