Mental Slowdown Can Begin in the 40s, Study Finds

Jan. 6, 2012— -- Call them senior moments, mental glitches or simple forgetfulness, many people have experienced the mental slowdown that can come with age.

New research finds that these cognitive slips can begin as early as age 45. But whether they are the result of dementia, cardiovascular disease or simply getting older is not clear.

Researchers studied a group of nearly 7,500 British government employees between the ages 45 and 70, periodically testing their memories, reasoning, vocabulary and comprehension skills for 10 years.

Overall, the 45- to 49-year-olds showed a decline of nearly 4 percent on average in their cognitive capabilities over 10 years.

That amount of decline is probably not enough to cause impairment in daily life, said study author Archana Singh-Manoux, research director of the Center for Research in Epidemiology and Population Health at Hopital Paul Brousse near Paris. But it could be an important red flag for future problems.

"This might well be part of the normal aging process," Singh-Manoux said. "However, other studies have shown that small differences in cognition might translate to greater differences in risk of dementia at older ages."

The study participants' cognition slipped even further as they got older. By age 65, men's cognitive performance declined by almost 10 percent, and women's dropped by 7.5 percent.

According to Singh-Manoux, this study, published today in the British Medical Journal, is the first to document cognitive declines at such a young age.

"The understanding of cognitive aging so far was of no cognitive decline until age 60," she said. "Our study shows that this is not the case. Cognitive function begins to decline earlier."

But how much that mental drop-off indicates a slide into more debilitating dementia is unclear. The current study didn't measure how many of the participants went on to develop dementia.

Dr. John Morris, director of the Alzheimer's Disease Research Center at Washington University in St. Louis, said the brains of people with and without dementia get smaller as they age, beginning as they reach middle age. He said it makes sense that the current study shows that there are cognitive declines that happen during that period as well.

"One wonders to what extent the people who are most likely experiencing this measurable cognitive decline are also the ones developing indicators for Alzheimer's disease, or who may accumulate enough brain damage to develop dementia," Morris said.

Previous research has shown that precursors to dementia can appear when people reach their late 20s or 30s. Some studies have also found characteristic traits of Alzheimer's disease, the most common form of dementia, in the brains of people in their mid-40s.

But cognitive decline may not be tied to dementia alone. Several studies have found that cardiovascular disease, such as high blood pressure and diabetes, might also take a toll on the brain or may even be linked to dementia. David Loewenstein, professor of psychiatry and behavioral sciences at the University of Miami, said lowering one's risk of cardiovascular disease may be one important way to also lower the risk of cognitive decline or dementia.

"Anything that's good for the heart is good for the brain," Loewenstein said. "This study does highlight the need for us to address health issues that may impact cognition, even at younger ages so that we set up the foundation for optimal cardiovascular and brain health."