Researchers are investigating a potential link between infections and Alzheimer’s, yet no conclusive evidence confirms a direct causal relationship (Illustrative Image Infobae)
According to the World Health Organization (WHO), the number of people worldwide living with dementia could reach 153 million by 2050, nearly triple the current figure. This surge is closely tied to the ageing of the global population and represents a growing challenge for public health. Currently, over 55 million people have the condition across the globe, and nearly ten million new cases appear each year, based on the WHO’s data.
Alzheimer’s disease is a form of dementia that affects memory, thinking, and behaviour. Over time, symptoms progress enough to disrupt day-to-day tasks.
A range of risk factors may contribute to the onset of Alzheimer’s, including age, genetic predisposition, head injuries, lifestyle habits, and potentially infections.
Risk Factors and Variations of Alzheimer’s
One classification distinguishes familial, hereditary Alzheimer’s from a sporadic type. Familial cases (autosomal dominant) comprise under 1% of total cases and stem from specific genetic alterations. The remaining 99% are described as sporadic, without a known definitive cause. Within this sporadic category, various elements have been linked to a higher likelihood of disease development, such as reduced educational attainment, physical inactivity, social isolation, hearing or vision loss, depression, and vascular risk factors. These vascular elements include high blood pressure, diabetes, dyslipidaemia, and obesity.
Recent research published in The Lancet Healthy Longevity underscores that preventive measures taken during youth can provide a robust first line of defence against cognitive decline and dementia later in life. Addressing factors like education, social engagement, and lifestyle early on might significantly affect long-term brain health.
Considering Infections and Inflammation
Some studies suggest that infections might influence Alzheimer’s risk. Although no direct causation has been established, certain reports link infections to the possible triggering of amyloid deposition in animal models. The real-world implications for humans remain unclear. Nonetheless, there are broader hypotheses about inflammation playing a role in Alzheimer’s—either as a trigger or an aggravating factor. One theory points to the central nervous system’s immune response, in which cells called microglia can become activated by inflammatory processes. While microglia primarily protect the brain from external threats, persistent inflammation might cause harm if it continues over an extended period.
Another idea examines the so-called gut–brain axis, which looks at how intestinal microbes and potential infections could spark inflammatory responses and possibly affect processes in the brain. Though investigations are ongoing, strong evidence of a direct infection-driven cause for Alzheimer’s does not currently exist. Instead, researchers focus on understanding inflammation’s broader contribution, including how it might be set off by various stressors, infections, or other triggers.
Common Risk Factors
Data from the Alzheimer’s Association indicate that most Alzheimer’s and other dementia cases result from a mix of influences, such as age, family history, genetics, and modifiable risk factors. Here are some key points:
- Age. Growing older remains the most recognised risk factor for Alzheimer’s and other dementias, but these conditions are not an inevitable part of ageing.
- Family History. Having a parent, sibling, or multiple relatives with Alzheimer’s can heighten one’s susceptibility to the disease. Modifiable factors—like sleep habits, tobacco use, hypertension, and diabetes—can further elevate that risk.
- Genetic Components. Two main types of genes are relevant: risk genes and deterministic genes. A small fraction of Alzheimer’s cases (fewer than 1%) stem directly from deterministic genes, which cause the disease outright. The rest arise from a more complex interplay of risk genes and environmental or lifestyle factors.
- Head Trauma. Past head injuries have been associated with an increased likelihood of cognitive disorders later in life.
- Medical Conditions Affecting Heart and Blood Vessels. Research increasingly supports the link between vascular health and the brain’s well-being. A compromised cardiovascular system—through illnesses like hypertension or diabetes—appears to heighten the risk of dementia.
How Alzheimer’s Develops
Alzheimer’s damages neurons in the brain, ultimately leading to their loss of function and eventual death. These neurons handle message transmission within the brain and between the brain and other body systems. Neurodegeneration, the process by which the disease attacks neurons, also affects synapses, where cells communicate with each other, further hampering cognitive abilities.
Two proteins—beta-amyloid and tau—are frequently cited in relation to Alzheimer’s:
- Beta-amyloid accumulates as plaques in the brain.
- Tau forms tangles within neurons.
Both phenomena contribute to the progressive decline in cognitive function characteristic of dementia. Additionally, ongoing research highlights the growing consensus that inflammation, or neuroinflammation, is a significant factor in Alzheimer’s progression. Beta-amyloid plaques, tau tangles, and certain microbes may all initiate or exacerbate this neuroinflammatory process.
More than 55 million people worldwide are living with Alzheimer’s or other dementias, and this figure could surpass 139 million by 2050 (Illustrative Image Infobae)
Potential Interaction with Infections
Although a definitive cause-effect relationship has yet to be established, certain infectious agents have attracted scientific interest. For instance, some studies explore whether bacteria from the gums or intestines might influence long-term cognitive health by fuelling inflammation or altering brain chemistry in ways that predispose individuals to Alzheimer’s. The precise mechanisms remain poorly understood and require further investigation.
Strategies to Reduce Alzheimer’s Risk
Managing vascular risk factors—like high blood pressure, unhealthy blood lipid levels, and excess weight—emerges as a top recommendation. Hearing or vision problems can also raise the disease’s likelihood, indicating the importance of regular check-ups and early interventions. Physical activity, social interaction, and cognitive stimulation play a crucial role in fortifying the brain. Programmes that incorporate these interventions, along with dietary guidance, have produced promising results in studies conducted in Europe, suggesting potential benefits on memory, executive function, and processing speed.
Quality sleep, generally defined as seven or more hours each night, is another pillar of prevention. During rest, the brain clears away waste products—including beta-amyloid. Issues such as sleep apnoea should be promptly addressed through medical consultation.
Stress management also supports brain health. Elevated stress levels can intensify inflammatory responses and trigger the production of harmful proteins. Techniques like meditation, mindfulness, or controlled breathing exercises can help.
A good night’s sleep is neuroprotective and helps the brain clear away waste products like beta-amyloid.
Specific Suggestions
- Prioritise Sleep: Aim for at least seven hours nightly. Rest allows the brain to remove toxins that accumulate during the day.
- Protect Your Head: Use helmets during activities where falls or collisions may occur. Seat belts in cars also reduce the risk of serious injuries.
- Manage Stress: Chronic stress can provoke cellular changes in emotionally reactive areas of the brain, promoting inflammation.
- Stay Socially Active: Social isolation has been linked to higher stress and inflammation, which, in turn, may influence cognitive impairment.
- Maintain Dental Health: Brushing and flossing regularly can help prevent gum disease, reducing harmful bacteria that may migrate and aggravate inflammation.
- Exercise Daily: Aerobic routines benefit both brain and cardiovascular health. Strength training provides additional neuroprotective effects.
- Learn Continuously: Formal education and ongoing learning appear to lower the risk of cognitive decline and dementia.
- Choose a Nutritious Diet: Limiting processed, salty, or sugary foods can reduce overall inflammatory stress on the body. Increasing consumption of vegetables, lean proteins, and whole grains offers broader health advantages.
- Keep Vaccinations Updated: Immunisations significantly cut the likelihood of severe infections, lowering potential inflammatory responses.
Good dental hygiene, including flossing, decreases the risk of gum disease, which raises levels of possibly harmful oral bacteria.
The evidence points to Alzheimer’s as a multifactorial condition, in which genetic, environmental, and lifestyle elements converge. Infections may be part of the picture, but no single factor alone appears to dictate the onset. Emphasising heart and brain care, nurturing social and intellectual engagement, and avoiding chronic stress or unmanaged health issues can all help reduce the disease’s risk. While there is still much to explore—particularly around how infections and inflammation may shape Alzheimer’s—focusing on holistic health measures remains the most effective current strategy for prevention.