The association of anxiety and depression with future dementia diagnosis: a case-control study in primary care

BACKGROUND Depression is identified as a risk factor for dementia. Little research has been carried out on the importance of anxiety, despite strong evidence of co-morbidity with depression. OBJECTIVE To examine the association of anxiety and depression with future dementia diagnosis. METHODS This case-control study was set in the Consultations in Primary Care Archive. Cases (n = 400), were patients aged >65 years old. About 1353 controls were matched to cases by gender, practice, age group and year of case diagnosis. Read codes of risk factors for dementia were searched in patient records. The associations of prior consultations for anxiety and depression, with future diagnosis of dementia were determined using multivariable logistic regression. RESULTS A past anxiety diagnosis was associated with a future dementia diagnosis [odds ratio 2.76 (95% confidence interval 2.11-3.62)]. The association of depression with dementia was attenuated by the high prevalence of anxiety within those who have depression. Including an interaction of depression and anxiety showed that having only depression was associated with future dementia diagnosis but a diagnosis of depression alongside anxiety did not increase the likelihood of a dementia diagnosis compared to having just an anxiety diagnosis. CONCLUSION Prior diagnosis of anxiety was strongly associated with dementia diagnosis after adjustment for other risk factors. The independent effect of depression was weaker compared to anxiety. Given the higher prevalence of anxiety primary care physicians should consider anxiety as well as depression as premorbid risk factors of dementia to improve early recognition and facilitate greater access to services.