Prevalence and incidence of dementia
Links between life experience and disease are identi-ed by means of observational, analytic and experimental approaches. Observational studies entail large-scale surveys to measure the frequency of dementia and to note correlations with sociodemographic, biometric and lifestyle variables. Surveys, while costly and time-consuming, are essential in conditions like dementia. Many cases go unrecognized by primary and specialist health services, even in high-income countries, and clinical registers are therefore not reliable sources of data (Ilie and Robinson, 2009; Knopman et al., 2011).