The rapid deterioration of our mental abilities as we age begins far earlier than scientists had suspected, Swedish researchers said on Wednesday.
Simple tests of perceptual speed, spatial ability and verbal function showed that some cognitive skills begin rapidly fading nearly 15 years before death, said Valgeir Thorvaldsson, who worked on the study.
“Previous studies have showed that the steep decline begins around five years before death,” said Thorvaldsson, a psychologist at Gothenburg University in Sweden. “What we could see in our data is that these changes occur much earlier than thought.”
Most people reach their mental peak between the ages of 35 and 40, then begin a steady decline that speeds up in the years before death, he said. The Swedish team wanted to test when that acceleration starts, in order to better understand the loss of mental ability.
In a 30-year study, the researchers tracked 288 men and women from age 70 until death, measuring their mental skills at regular intervals.
They found perceptual speed, a measure of how quickly people can compare figures, deteriorated rapidly from about 15 years before death. Spatial ability began to decline fast about eight years pre-death, and verbal skills nearly seven years before.
“There is substantial acceleration in cognitive decline many years prior to death among individuals without dementia,” Thorvaldsson and colleagues wrote in the journal Neurology.
Lack of exercise and mental stimulation in old age, and increasing health problems, may help explain what triggers that final decline, Thorvaldsson added in a telephone interview.
Tracking when the rapid change begins could help doctors identify people likely to encounter severe health problems in the near future, he said.
“A change in verbal ability might therefore be considered a critical marker for degeneration in health in older people,” Thorvaldsson said.