Prescription Drugs Tied to Lower Dementia Risk

There's currently no cure for dementia. Although some recently developed drugs show promise in slowing the progress of the disease, these are both costly and may have limited benefit for many patients.

However, a recent Cambridge-led study has found a link between commonly used prescription drugs - including antibiotics, antivirals and vaccines - and a lower risk of dementia.

Given these drugs are already licensed and their safety profiles well established, this could enable faster and more cost-effective clinical trials in the search for a cure.

The study analysed health data from 130 million people, including one million people who had been diagnosed with dementia. Having identified possible links with prescription drugs and dementia risk, the researchers conducted a systematic review of 14 studies to explore these links further and understand which prescription drugs might affect dementia outcomes.

This led them to the conclusion that antibiotics, antivirals and anti-inflammatory drugs were all associated with reduced dementia risk. The researchers also found a link between the hepatitis A, typhoid and diphtheria vaccines and lower dementia risk.

It's unknown how long participants had been taking any of these prescription drugs or how many times they'd been prescribed them during their lifetime, so it will be important for future studies to investigate these factors.

Immune reponse and brain health

Based on their findings, the researchers suggest that the protective effects that these prescription drugs appear to have may be because they reduce inflammation, control infections and improve overall brain health.

This supports the theory that common types of dementia could be triggered by viral or bacterial infections . We know that infections that last a few days to several weeks, whether bacterial or viral, can cause great damage to the brain . This is because infections cause an enhanced immune response from the body, which can damage brain cells - disrupting brain connections and accelerating memory decline .

Antivirals and antibiotics help combat infections, which in turn may dampen this excessive immune response. Meanwhile, vaccines can prevent these infections from occurring in the first place. In both cases, this can significantly reduce the risk of prolonged infections and their potentially devastating consequences for brain health .

It's also worth noting that other studies have also shown an association between the BCG vaccine, which protects against tuberculosis, and a decreased risk of Alzheimer's (a type of dementia).

Inflammation and dementia risk

Regarding the new study's finding of a link between the use of anti-inflammatory medications and a reduced risk of dementia, notably non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen were identified as potentially protecting against memory decline.

Again, this is another piece of evidence suggesting that inflammation plays a central role in dementia . Inflammation is the body's natural way of defending itself against injury or infection. But when inflammation lasts too long, it can cause harm - particularly to the brain. Long-lasting inflammation releases chemicals that can damage healthy tissue . These chemicals can damage brain cells and disrupt communication between them, which leads to memory loss.

Anti-inflammatory drugs work by blocking the production of certain molecules that cause inflammation . By doing this, they might help protect brain cells from damage caused by long-term inflammation.

Next steps

The evidence for the benefits of other types of drugs on dementia risk was less consistent. The study found that certain blood-pressure drugs, antidepressants and diabetes drugs were linked to both a lower and higher risk of dementia.

One possible reason is that these prescription drugs affect different biological processes. Even drugs designed to treat the same condition may target different biological mechanisms, which might explain the varying results.

For example, some blood pressure medications - such as ACE inhibitors and angiotensin II receptor blockers (ARBs) - improve brain health by enhancing blood flow and reducing inflammation. On the other hand, beta-blockers primarily lower heart rate and may not provide the same neuroprotective benefits.

Diabetes drugs also had mixed associations with dementia risk. But as people with diabetes are already at a higher risk of developing dementia, this makes it difficult to determine whether this association was due to the effects of the drugs themselves, or if diabetes is the main factor at play.

Overall, more research is needed to confirm this study's findings and better understand how all these drugs appear to influence dementia risk. Randomised controlled trials will be crucial to see if these prescription drugs really can be repurposed to prevent dementia effectively. At the same time, looking into the biological mechanisms that are potentially affected by these drugs could shed light on the causes of dementia.

This research highlights the importance of addressing inflammation and infections as part of a broader strategy for maintaining brain health. And by finding new uses for existing drugs, scientists could deliver treatments to patients more quickly - offering hope in the fight against dementia.

Rahul Sidhu does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.