One headline reads “Dementia’s first signs appear long before old age, study finds.” (Bloomberg) Alternatively, another headline reads that “Cognitive decline can start at age 45.” (Medscape). These differing interpretations are the leads for two “alerts” I follow to try to keep up with current topics related to memory and aging. In both cases, the actual data are the same and come from a recent article published in The British Medical Journal.

The headlines are based on a large, prospectively designed longitudinal study of more than 7,000 volunteers aged 45-70. Each participant (ranging in age from 45 – 70) underwent cognitive assessment three times during ten years. Overall scores on tests of memory and reasoning declined during the ten years. Only scores on tests of vocabulary remained stable.

On face value these findings appear to be worrisome. However, on closer inspection, the changes were small for men and women between the ages of 45-49 (3.6%). As might be expected, the decline was greater in those aged 65-70 years (a drop of 7.4% for women and 9.6% for men). These are not dramatic changes even in the older participants (some of whom may have actually been in the early stages of decline).

It’s important to realize that not all individuals declined. The percentages are based on averages which mean some declined more and some less than the average – and some improved their scores. Furthermore, there were over 7,000 enrolled in the study. That means that small changes can be statistically significant. But this begs the question of whether small changes like these are important. The risk from such large studies is that trivial effects can be over interpreted as being of practical importance.

To equate these changes – even for the older participants – with “dementia’s first signs” is clearly not justified by the findings. Dementia marks a severe decline that compromises independence. Dementia is not the same as changes that result from normal aging. It seems clear to me that we are justified in saying that tending to cognitive abilities and brain function needs to start in middle age or earlier. But to say the first signs of dementia start at 45 is needlessly alarming. We are not destined to become demented and it is not downhill for all of us after 45.