Lower IQ in children is a possible risk factor for vascular dementia later in life, according to a new study.
Vascular dementia is the most common kind of dementia after Alzheimer's and occurs when blood flow to the brain is impaired.
The study, by researchers at the University of Edinburgh, examined 173 people who took a test of their mental ability in 1932 when they were about 11 years old and later developed dementia.
This group was compared to one set of control participants of the same age and gender. For another group of controls, the researchers made sure that the cases and controls came from families where the fathers had similar types of occupations.
People with vascular dementia were 40 percent more likely to have low-test scores when they were children than the people who did not develop dementia. This difference was not true for those with Alzheimer's disease.
"These results point to the importance of reducing the vascular risk factors that can lead to strokes and dementia," said the study's author John M. Starr. "Risk factors include high blood pressure, high cholesterol and smoking."
Starr said the findings support the hypothesis that low childhood IQ acts as a risk factor for dementia through vascular risks rather than the "cognitive reserve" theory.
This theory speculates that greater IQ and education create a buffer against the effects of dementia in the brain, allowing people to stay free of signs of dementia longer even though the disease has started affecting their brains.
The findings of the study have been published in the online issue of the journal Neurology.