Maintaining a healthy weight during middle age may delay the onset of Alzheimer's disease, a new study has found.

While obesity is known to increase the risk of developing Alzheimer's disease, until now, it has been unclear whether it also affects the age at onset of the disease.

Researchers decided to look into this further. They followed the progress of almost 1,400 people over a period of nearly 14 years, during which time, 142 developed Alzheimer's disease.

They found that obesity during midlife appeared to increase the risk of developing Alzheimer's disease at an earlier age. In fact, for each unit increase in the participants' body mass index (BMI) during middle age, the onset of Alzheimer's was found to accelerate by 6.7 months.

In other words, the more a person weighed during middle age, the earlier they went on to develop Alzheimer's disease.

Those who were obese during midlife were also found to have higher measurements of fibrillar amyloid, a sign of damage in patients with Alzheimer's.

The researchers concluded that ‘midlife overweight predicts earlier onset of Alzheimer disease and greater burden of Alzheimer neuropathology'.

"A healthy BMI at midlife may delay the onset of Alzheimer's disease. Our findings raise the possibility that inexpensive, non-invasive interventions targeting midlife obesity and overweight could substantially alter the trajectory of Alzheimer's disease, reducing its global public health and economic impact," they said.

Details of these findings are published in the journal, Molecular Psychology.

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