Good news, bad news

The good news is that the prevalence of dementia among those over 65 has gone done by about 24% according to a study A Comparison of the Prevalence of Dementia in the United States in 2000 and 2012 published in January 2017.

Dementia decreased from 11.6% to 8.8% between 2000 and 2012, representing an absolute decrease of 2.8 percentage points, and a relative decrease of about 24%. This study supports the notion that “cognitive reserve” resulting from early-life and lifelong education and cognitive stimulation may be a potent strategy for the primary prevention of dementia in both high- and low-income countries around the world. 

Educational attainment increased significantly, with those 65 years or older in 2012 having nearly 1 additional year of education compared with the 2000 cohort. 

Higher levels of educational attainment are also associated with health behaviours (eg, physical activity, diet, and smoking), more cognitively-complex occupations, and better access to health care, all of which may play a role in decreasing lifetime dementia risk.

The bad news is that the prevalence of obesity and diabetes among those 65 years or older increased significantly between 2000 and 2012, and diabetes was associated with 39% higher odds of dementia, after controlling for all other factors. As in prior studies among older adults, we found that obesity was associated with a decreased risk of dementia, consistent with the hypothesis that, while obesity in mid-life may increase the risk for late-life cognitive decline and dementia, obesity at older ages may be associated with cognitive and other health advantages.

The declining risk for dementia in the face of a large increase in the prevalence of diabetes suggests that improvements in treatments between 2000 and 2012 may have decreased dementia risk, along with the documented declines in the incidence of common diabetes-related complications, such as heart attack, stroke, and amputations.

The finding of a significant decline between 2000 and 2012 of the heart disease-related OR for dementia would also be consistent with improved cardiovascular treatments leading to a decline in dementia risk. 

The findings are consistent with those of a number of recent studies that also found declines in dementia incidence or prevalence in high-income countries around the world.