This study result is contrary to the mainstream view, which is that absent advances in medicine the risk of suffering dementia will continue to rise along with life span. However, it makes sense from a reliability theory point of view; if aging and dysfunction and life span are all consequences of the level of damage suffered in cells and molecular machinery, then reducing that damage should extend life by slowing aging and also reducing dysfunction.
The risk of developing dementia may have declined over the past 20 years, in direct contrast to what many previously assumed. The result is based on data from SNAC-K, an ongoing study on aging and health that started in 1987.
"We know that cardiovascular disease is an important risk factor for dementia. The suggested decrease in dementia risk coincides with the general reduction in cardiovascular disease over recent decades. Health check-ups and cardiovascular disease prevention have improved significantly in Sweden, and we now see results of this improvement reflected in the risk of developing dementia."
The result shows the prevalence of dementia was stable in both men and women across all age groups after age 75 during the entire study period (1987-1989 and 2001-2004), despite the fact that the survival of persons with dementia increased since the end of the 1980s. This means that the overall risk of developing dementia must have declined during the period, possibly thanks to prevention and better treatment of cardiovascular disease.
"The reduction of dementia risk is a positive phenomenon, but it is important to remember that the number of people with dementia will continue to rise along with the increase in life expectancy and absolute numbers of people over age 75."