If you're in your 40's and feeling like your mind is just not as sharp as it was when you were younger, it may not be your imagination.
A new study shows that mental decline can begin at the age of 45.
Researchers studied more than 7,000 British men and women between the ages of 45 and 70, for 10 years.
They were tested on memory, vocabulary and hearing and comprehension.
Researchers found a 3.6% decline in mental reasoning in both sexes between the ages of 45 and 49.
They concluded that cognitive decline can begin as early as age 45.
Between the ages of 65 and 70, the men in the study showed a 9.6% decline in mental reasoning.
The figure was 7.4% for women.
Previously researchers have said cognitive decline is rare before age 60.
This research is important because mental decline in some cases can be stopped with certain medications or behavior changes.
But researchers add that medical interventions are more likely to work at the first signs of mental impairment.
While some memory loss is inevitable, doctors say a healthy physical and mental lifestyle will help.
Eating foods that are good for the heart, such as fruits, vegetables and whole grains is also important, because it could protect brain cells from age-related decline.
The study is published in the journal BMJ.