Burden of Alzheimer's disease: population-based estimates and projections for New Zealand, 2006-2031

OBJECTIVE: To estimate the burden of Alzheimer's disease (AD, including 'mixed' dementia) in New Zealand in 2006, and project this burden out to 2031. METHOD: An incidence to prevalence methodology was utilized, the foundation of which is a discrete time Markov model allowing for multiple stages of disease (early vs late). Population estimates and projections, and all-cause mortality rates, were obtained from Statistics New Zealand. In the absence of usable New Zealand data, data on disease incidence and progression were obtained from systematic reviews of the international (mainly European, Australian and North American) literature. Projection scenarios included a demographic scenario in which change resulted only from increases in population size and ageing; a prevention scenario in which incidence rates were reduced by 25% from 2011; a treatment scenario in which disease progression rates were likewise reduced by 25% from 2011; and a combined scenario capturing both interventions. RESULTS: The model estimated that approximately 28000 people are currently living with AD (whether formally diagnosed or not), approximately 55% in the early and 45% in the late stage of the disease; approximately 6600 people newly develop AD each year; and approximately 2300 people die from (as opposed to with) this condition. The model projected that the prevalence of AD will increase approximately 2.5-fold (to approx. 70000 people) by 2031, if demographic drivers are unopposed. Plausible improvements in prevention and treatment, however, acting together, could reduce this growth by up to 50%, so that the prevalence of AD only doubles. CONCLUSION: Even this more optimistic projection has profound implications for the funding and provision of dementia care services, as well as for patients, their families, informal carers and the psychogeriatric workforce. New service configurations and models of care will be necessary. Access, quality and coordination standards for home care, day care, respite care, residential care and specialist services (including memory clinics) will need to respond accordingly.