If you have lower levels of a type of cholesterol nicknamed ‘bad’ cholesterol in your blood, you may be less likely to develop dementia – and vice versa.
That’s according to a recent Korean study published in the Journal of Neurology, Neurosurgery and Psychiatry.
Experts know that low-density lipoprotein cholesterol (LDL-C) levels are linked to heart health, but its relationship to brain health and dementia is less certain.
To investigate this, scientists analysed data collected from 11 university hospitals in South Korea, on 571,000 adults without dementia.
They put these adults into two groups according to cholesterol tests at the start of the study. One group had high LDL-C, defined as more than 3.4 mmol/L or 130mg/dL, and the other had low LDL-C, defined as less than 1.8 mmol/L or 70mg/dL.
After six months or more, people with low levels LDL-C were found to be 26 per cent less likely to be diagnosed with any type of dementia, and 28 per cent less likely to be diagnosed with Alzheimer’s disease, compared to those in the high LDL-C group.
But this wasn’t a case of ‘the lower the better.’ Adults with very low LDL-C levels (below 1.4 mmol/L or 55mg/dL) were only 18 per cent less likely to develop dementia compared to those in the high cholesterol group. And people with extremely low LDL-C levels (below 0.8 mmol/L or 30mg/dL) had the same level of dementia risk as those in the high LDL-C group.
The scientists also found that statins – medication used to lower LDL-C levels – seemed to have a protective effect among people who already had low LDL-C levels.
Those in the low LDL-C group who were taking statins had a 13 per cent lower risk of dementia, and 12 per cent lower risk of Alzheimer’s, compared to adults not taking statins.
The study concluded that low LDL-C levels were significantly associated with a reduced risk of dementia, and that statins could provide additional protection against the disease.
But Dr Petra Proitsi – a genetic epidemiologist at the Centre for Preventive Neurology at Queen Mary University of London, who was not involved in this research – told BBC Science Focus that there were several limitations to the study.
For instance, this was a retrospective study, which means there were several factors that the authors didn’t measure that might have affected their results, such as age, sex, genetic risk of dementia and lifestyle factors.
This study can't tell us whether more LDL-C actually caused higher dementia risk, or how this might happen.
Proitsi added: “The study measured LDL-C levels at a single time-point. Other studies have reported non-linear relationships, and the lack of longitudinal data limits the ability to properly model these relationships.” In other words, the relationship between LDL-C and dementia might be more complicated than this study allowed for.
However, she continued: "Large-scale studies using real-world data are certainly welcome – especially those that include insights from diverse ethnic groups. The relationship between cholesterol and dementia remains complex and requires careful, in-depth investigation."
Read more:
- Here's how your cholesterol level shapes your dementia risk
- Scientists (and taxi drivers) may have discovered the secret to beating dementia
- Dementia breakthrough: Science can now measure your brain’s true ‘biological age’
About our expert:
Dr Petra Proitsi is a Reader in Genetic Epidemiology at Queen Mary University of London's Centre for Preventive Neurology. She is also Deputy Lead for the Digital and Health Data Science Theme at the Wolfson Institute of Population Health. She has a PhD in neuroscience from King's College London.
