Time to keep an eye on your cholesterol! A new Lancet Commission report highlights high cholesterol and untreated vision loss as major new risks for dementia, which affects memory and thinking skills. Alzheimer’s Disease, the most common type of dementia, makes up 60-70% of cases. The report shows that these issues account for nine percent of all dementia cases. Seven percent of dementia cases are linked to high levels of bad cholesterol (LDL) that often rise around age 40, while untreated vision problems contribute to two percent of cases. So, keep those cholesterol levels in check and get those eyes examined.

Understanding the Link Between Cholesterol and Dementia

The report, written by 27 top dementia experts, underscores the importance of managing cholesterol and addressing vision issues to lower the risk of developing dementia. With dementia listed as the seventh leading cause of death worldwide by the World Health Organization (WHO), this new research is particularly relevant for India.

Suvarna Alladi, a professor of neurology at NIMHANS in Bengaluru and a key author of the report, points out that dementia affects 7.4% of people over 60 in India, with around 8.8 million individuals living with the condition. “Age remains the strongest risk factor for dementia, but this new evidence highlights why we need to prioritise screening and treating vision loss and managing cholesterol levels in older adults to help reduce dementia cases,” she says.

In 2020, the Lancet Commission identified 12 key risk factors for dementia, including low levels of education, hearing impairment, high blood pressure, smoking, obesity, depression, physical inactivity, diabetes, excessive alcohol consumption, traumatic brain injury (TBI), air pollution, and social isolation.

Role of Vision Loss and Cholesterol in Cognitive Decline

A meta-analysis of three UK studies involving over 1.1 million people under 65 found that every 1 mmol/L increase in LDL cholesterol raised dementia risk by eight percent. Another study with 1.2 million participants showed that LDL cholesterol levels over 3 mmol/L increased the risk of dementia by 33 percent. Additionally, a large UK study of 1.8 million people tracked for 7.4 years confirmed that higher LDL cholesterol levels are linked to a greater risk of dementia. Researchers say this connection arises because excess cholesterol raises stroke risk and leads to the buildup of amyloid β and tau proteins, which disrupt brain cell function.

High levels of LDL cholesterol are linked to increased amyloid buildup in the brain. “Several factors explain the connection between high LDL cholesterol (levels above 100 mg/dL) and brain amyloid accumulation,” says Dr. Faheem Arshad, assistant professor of neurology at NIMHANS. These include heightened activity of amyloid-producing enzymes like secretases, reduced clearance of amyloid from the brain, negative impacts on neuron cells, and damage to the blood-brain barrier due to inflammatory processes.

Researchers highlight that “individual counselling on diet and exercise has limited effects on lowering LDL cholesterol. Statins, which are being studied for their potential benefits in Alzheimer’s Disease, show promise due to their anti-inflammatory and antioxidant properties, in addition to reducing cholesterol levels.” So, what’s the connection between dementia and untreated vision loss? The study suggests that vision loss might be linked to conditions like diabetes, which is a known dementia risk factor. There could also be an underlying issue affecting both the retina and the brain.

Dr. Arshad notes that correcting vision problems, such as refractive errors, might slow cognitive decline by enhancing sensory input. “This is a bidirectional relationship since cognitive factors also impact visual processing. Areas of the brain involved in memory and language influence how we perceive and interpret visual information. Thus, sensory deprivation can speed up cognitive decline. Age-related sensory impairments are influenced by both biological and environmental factors,” he explains.

Dr Arshad adds that both cognitive and sensory dysfunctions are triggered by ageing, external factors (like alcohol and smoking), neurodegenerative disorders, and biological factors. “Sensory and cognitive impairments are interconnected, with each affecting the other in various ways. Addressing these issues requires a comprehensive approach that takes their complex interplay into account,” he concludes.

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