Today’s projections of the scale of the incoming dementia epidemic assume that the age and sex related variables will remain constant over time, with the aging population alone driving the projected increase. Drawing from recent studies, there is moderately consistent evidence that dementia incidence is declining in high-income countries. Consistent with worsening cardiovascular risk factor profiles in East Asia, there is some evidence that suggest increasing prevalence of dementia in that region. Let’s expand the current trends in prevalence in incidence of dementia, and the survival with this illness.

Background

The basis for assumption that age- and sex- specific prevalence of dementia will remain unchanged over time comes from studies, including those published by Alzheimer’s Disease International (ADI) that compare gradual decrease or increase in prevalence over long time periods. The prevalence of dementia, or the proportion of the population affected at a point of time, is a product of its incidence and the average duration of the disease episode, from incidence to death. A decline in age-specific incidence is possible, if we tackle the exposure to suspected elements such as low education in early life, hypertension in midlife and smoking and diabetes.

Dementia prevalence

In the Medical Research Council Cognitive Function and Ageing Study (MRC CFAS) study, a statistical decline in the prevalence of dementia was noticed between 1993 and 2011, which was consistent with a larger but statistically insignificant decline in prevalence in Zaragoza, Spain and a decline in the prevalence of moderate-to-severe cognitive impairment seen in the Health and Retirement Study (HRS) in the United States. Contrasting this, three studies from Sweden and the U.S. indicate a stable prevalence of dementia, while a Japanese study of secular trends found an increase in dementia prevalence of 23% between 1980 and 2000.

Dementia incidence

Two U.S. population-based studies, one of African American population in Indianapolis, IN, and the other derived from the Framingham Heart Study, provided a statistically significant basis for reduction in the incidence of dementia. A similar annual rate of decline in dementia incidence (-3.0%) was reported in an analysis od German insurance claims data. Repeated surveys in Stockholm, Sweden, are also provide data consistent with a decline in dementia incidence. On the other hand, population-based studies in Ibadan, Nigeria and Chicago, IL, USA, indicated a stout incidence of dementia over 11-year periods.

Dementia care programs

Care programs for people with dementia are focused on individual needs, high quality environments, leading staff to resident ratios, as well as deep resident knowledge and connection. A prerequisite for an effective contemporary program, as the one conducted at Mark Moran Vaucluse aged care centre, is highly trained staff who offer 24-hr clinical support, providing stability and peace of mind of the residents and their families. The environment for such a high-standard facility is conceived on light-filled spaces, a calming palette of blues and greens, that work together to an uplifting backdrop, while private gardens offer a relaxing space where residents can enjoy spending time in nature.

Potential for prevention

The future course of the global dementia epidemic up to 2050 is greatly dependent on the continuing effort to improve public health. People who’ll be reaching their senior years in 2050 were born in the 1970s and have received good education. Now being in the fourth and fifth decade of life, which is a critical ‘sensitive period’ in which evidence suggests that efforts to detect, prevent and control obesity, hypertension, and diabetes are likely to have the strongest positive impact upon dementia risk in later life.

A desirable outcome for public health

One of the indications for successful dementia risk reduction might be that the incidence of dementia is being delayed to older ages. In this way, the average age of onset may increase over time. Although age-specific and age-standardised mortality for people with dementia might remain unchanged, for all people with dementia, mortality may be higher and survival shorter, as the onset is occurring closer to the natural end of life. In his article published at the Journal of Alzheimer Association, Kenneth M. Langa describes this phenomenon as ‘the compression of cognitive morbidity’ which is a desirable outcome for public health, with fewer years spent in reduced independence.

The available evidence suggests that the age-specific prevalence of dementia is very unlikely to change significantly in coming years, even if the incidence of dementia can be traced to the response of secular improvements in public health in high-income countries. Future projections for low- and middle-income countries might turn conservative, unless effective public health action is taken.