In Australia, it has beens estimated that 9% of people aged over 65, and 30% of those aged over 85 have dementia. However, these estimates are largely based on older data from other countries, or small local samples.
A new technique based on an ecological method for estimating species population size has been used to estimate dementia rates in the Australian population. The study used 16 years of data from 12,432 Australian women born between 1921 and 1926 who participated in the Women's Health Australia study. Survey data was linked to aged care assessments, the National Death Index, the Pharmaceutical Benefits Scheme, and hospital admissions data to find any instance where the women participating in the study were diagnosed with dementia. This additional data helped overcome the problem of such studies, where participants often just drop out, and the cause isn’t known.
Applying the ecological technique to all this data led to the conclusion that an additional 728 women with dementia had not been identified, increasing the 16 year prevalence from 20.4 to 26.0%. Breaking this down by age, we have:
- 70-74: 0.3%
- 75-79: 3.7%
- 80-84: 16.6%
- 85+: 31%
 . Estimating the prevalence of dementia using multiple linked administrative health records and capture–recapture methodology. Emerging Themes in Epidemiology [Internet]. 2017 ;14:3. Available from: http://dx.doi.org/10.1186/s12982-017-0057-3