BMI declines 7 years before cognitive impairment, study finds

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Body mass index (BMI) is a value derived from the mass and height of a person.

The BMI is defined as the body mass divided by the square of the body height and is expressed in units of kg/m², resulting from mass in kilograms and height in meters.

In a study from Karolinska Institutet, scientists found much lower BMI occurs beginning about 7 years before a diagnosis of mild cognitive impairment (MCI).

They assessed the long-term BMI trajectories preceding incident MCI and dementia. The analysis included 1,390 adults (mean age, 78.4 years; 76.5 percent female).

The researchers found that compared with participants who remained cognitively intact, BMI tended to decline earlier and faster in those with incident MCI.

People with incident MCI had an associated much lower BMI from seven years before diagnosis than those who were cognitively intact.

However, the slopes of BMI decline did not differ strongly between those with incident MCI who did and did not develop dementia.

In a subset of 358 people with autopsy data, BMI was associated with a faster declination among participants with a high burden of global Alzheimer’s disease pathology or vascular pathology.

These findings suggest that the high levels of Alzheimer’s disease pathology or cerebral vascular disease pathology may be associated with the BMI decline preceding MCI.

Future imaging studies (e.g., using positron emission tomography) are warranted to clarify the temporal association between BMI change and brain pathologies.

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The study was conducted by Jie Guo et al and published in JAMA Psychiatry.

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