Double compression: a vision for compressing morbidity and caregiving in dementia.

The anticipated rise of dementia prevalence due to global aging may be tackled by morbidity compression through lifestyle changes (i.e., consistent participation in physical and intellectual activities) that promote cognitive reserve. A hypothetical model of cognitive decline due to Alzheimer's disease (AD) and modulation of the clinical trajectory by cognitive reserve is presented. People with higher cognitive reserve are expected to show delay of the mild cognitive impairment phase but faster conversion to AD thereafter. Once conversion to AD is evident, there would be even faster deterioration, resulting in compression of morbidity. When morbidity is compressed, not only is prevalence reduced but the caregiving load is also compressed; this is referred to as "double compression." Research and policy directions are discussed.