A new study published in the journal Alzheimer's and Dementia links high cholesterol with a lower risk of cognitive decline for people over 85 years old. But that might not necessarily mean that having high cholesterol prevents dementia.
The study authors compared the cognitive function of people in different age groups. By analyzing existing data from the Framingham Heart Study, they evaluated the cholesterol levels of Framingham subjects at different ages. "Midlife" cholesterol was recorded at around 40 years old while "late-life" cholesterol was recorded at around 75.
They were surprised to find that for people aged 85 to 94 years old, having higher late-life than midlife cholesterol was correlated with a 32 percent lower risk of cognitive decline. In other words, higher cholesterol among the very old was associated with a reduced chance for dementia.
The results for people 10 years younger, however, looked much different. Study participants aged 75 to 84 years old with higher late-life cholesterol texperienced a 50 percent higher risk of cognitive decline.
What do scientists make of these seemingly contradictory results?
Jeremy Silverman, lead author of the study, posits that the correlations are a result of the "protected survivor model." This model suggests that those who are protected, perhaps genetically (though scientists aren't sure), against the potentially harmful effects of high cholesterol on cognition are more likely to live into very old age - past 85 years old - and are disproportionately represented in that oldest population.
"Most people prior to late old age are vulnerable to the deleterious effects of total cholesterol," Silverman explained to The Daily Meal. "There is a group of people that, up through early old age, are only a small minority, [but] who, perhaps owing to their genes, are protected against these bad effects."
So there may be some other influence at play - and Silverman warns that "we don't think increased cholesterol becomes a good thing for cognition, or [is] protective, for the oldest-old."
Conversely, he noted, the study suggests that "having high cholesterol need not be a serious source of concern" for dementia prevention.
This wouldn't be the first time science has muddied the waters on what does and does not preserve brain health.
In fact, studies often butt heads when it comes to dementia prevention. Wine, for instance, has been controversial in this arena. While some studies indicate that moderate consumption of wine could help stave off dementia, others are hesitant to make the connection. (Some studies also imply that no matter what type of alcohol you're drinking, a little booze could help keep your brain sharp.)
Some diets, such as the Mediterranean diet, have been shown to potentially help with dementia prevention, but other studies suggest that lifestyle changes, not diet, are the most influential method of protection from the condition.
Science does suggest, though, that adding certain foods to your diet could help stave off Alzheimer's and other forms of cognitive decline.