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Fluctuating cholesterol, measured annually, may be a new biomarker for identifying people at risk of dementia, according to a study of 9,846 people aged 65 years and older.

At baseline, patients (median age 73.9 years) did not have dementia or other memory problems. Researchers measured total cholesterol levels and at three annual visits.

Patients were followed for an average of 5.5 years after the third visit and undertook memory tests annually. Those prescribed statins during the study could take part but the researchers could not assess statin adherence or dose changes.

Participants were divided into four groups based on the change between their first and fourth total cholesterol measurements. The average difference between consecutive yearly measurements was 22 and 91mg/dL in the groups with the smallest and largest total cholesterol change respectively.

During the study, 509 people developed dementia: 7.1 and 11.3 per 1,000 person-years in those with the least and greatest variability in total cholesterol respectively. 

After adjusting for other factors that affect dementia risk, such as age, smoking and hypertension, people with the greatest total cholesterol variability were 60 per cent more likely to develop dementia than those with the most stable concentrations. 

People with the greatest variability in low-density lipoprotein cholesterol (LDL-C) were 48 per cent more likely to develop dementia than those with the least variation, according to the research.

People who showed the greatest variability in total cholesterol and LDL-C were 23 and 27 per cent more likely to develop cognitive impairment or memory problems that did not meet the criteria for dementia than those with the most stable levels. 

The study does not prove that variable total cholesterol levels cause dementia.