Time trends in incidence and survival rate for developing dementia of people presenting with reported memory concern and cognitive decline in UK primary care

Problem

Dementia is the leading cause of death, having recently exceeded Ischaemic heart disease. People with subjective memory complaints affects approximately 25-50% of people aged 65 and over and are twice as likely to develop dementia within 5 years, compared to cognitively healthy older adults. People with mild cognitive impairment affects approximately 5-20% and are also at increased risk of developing dementia. While there is some understanding of the incidence of people with memory complaints and cognitive decline (not dementia) in the community, there has been limited research in relation to those who present to primary care. The study will report the time trends of people with reported memory concern and cognitive decline in UK primary care between 2009-2018. Secondly, the study will examine the survival time to dementia.

Approach

Individuals who contributed to data within IQVIA medical research database from 1st January 2009 to 31st December 2018 and aged 65-99 years will be included for a retrospective cohort study. IQVIA medical research database collects longitudinal data on over 18 million anonymised patient records across 790 UK general practices. A panel of 4 professionals consulted on suitable Read codes to form case definitions of memory concern, cognitive decline and Dementia. Crude incidence was calculated and differences of incidence rate ratios between groups was examined with a Negative Binomial regression. Survival analysis of time to incident dementia from recorded memory concern and cognitive decline was calculated using a Fine and Grey model, with competing risk of death.

Findings

Incidence rate of recorded memory concern remained stable but with a slight decline from 2009 (HR 8.47, 95% CI 8.26 to 8.69) to 2018 (HR 7.63, 95% CI 7.36 to 7.92). In contrast, the incidence rate of recorded cognitive decline increased with each passing year from 2009 (HR 1.32, 95% CI 1.24 to 1.41) to 2018 (HR 3.50, 95% CI 3.32 to 3.69). Between ages 65- 79, people with cognitive decline are at a increased risk of incident dementia compared to people with memory concern. However, by ages 80-99, people with cognitive decline became a lower risk of incident dementia compared to memory concern.

Consequences

Incidence rates of memory concern and cognitive decline are lower than community-based studies suggesting that either not enough people are presenting to primary care with memory problems or are not being recorded in GP notes. There is still a need to increase the identification of memory concern and cognitive decline and improve the use of Read codes in primary care for this high-risk group in order to deliver earlier dementia prevention advice.