Despite years of research, science still doesn’t really know why we suffer cognitive decline—such as losing our memory or being unable to solve simple problems—as we get older.
The usual suspects of obesity, smoking and sedentary living account for less than 6 percent of cases of cognitive decline in people aged between 54 and 85, say researchers at Ohio State University.
And factors such as socio-economic status, level of education and race explained just 38 percent of the difference in cognitive functioning in people who were tested when they were 54 years old.
“There’s still a lot we don’t know about why cognitive functioning varies so much between older adults,” said Hui Zheng, one of the researchers.
They analysed data from 7068 participants who were born between 1931 and 1941, and assessed their cognitive function when they were 54 and any decline until they reached the age of 85.
The level of education was the single biggest predictor of cognitive decline, and this explained around 25 percent of the difference between people, and this was followed by race, household income, occupation and depression.
But chronic disease, healthy habits, gender and religious faith—often put forward as major influences—were responsible for just 5 percent of the differences as the group got older.
And cognitive decline shouldn’t be confused with dementia and Alzheimer’s: together, they account for just 41 percent of cases. Instead, non-dementia cognitive decline seems to be very common in older people—and still we don’t know why.