Prescribing of dementia drugs in Alzheimer’s disease is 50% higher than expected, a new analysis of NHS data has revealed.
The analysis of data from 2012 found prescribing rates of donepezil, galantamine, rivastigmine and memantine were 50% higher than expected when compared with prevalence rates of Alzheimer’s disease.
The analysis takes into account the recommendation by NICE in 2011 that patients with mild forms of Alzheimer’s disease be prescribed dementia drugs, lifting previous controversial restrictions on the use of drugs in patients with less severe Alzheimer’s.
Experts say that the discrepancy may be because of rising prevalence rates, and an underestimation by analysts of the number of people with Alzheimer’s disease.
The data come amid the Government’s drive to increase diagnosis rates for dementia, based on figures that show a variation in the expected rates of dementia versus those identified.
The data published this week as part of an analysis of the use of NICE-approved medicines by the Health and Social Care Information Centre (HSCIC) look at the ratio between expected use and observed use of medicines in the NHS.
The most ‘over-used’ medicines were donepezil, galantamine, rivastigmine and memantine with a ratio of 1.48.
The analysis showed the proportion of patients with mild Alzheimer’s disease taking cholinesterase inhibitors was 92.7%. The proportion treated with donepezil was 68.7%, the proportion treated with galantamine was 20.1% and the proportion treated with rivastigmine was 11.2%.
In moderate Alzheimer’s disease, the proportion of people treated with memantine was 21.6%, the proportion treated with cholinesterase inhibitors was 78.4%, the proportion treated with donepezil was 68.7%, the proportion treated with galantamine was 20.1% and the proportion treated with rivastigmine was 11.2%.
In severe Alzheimer´s disease, the proportion of people treated with memantine was 31%.
Professor Steve Iliffe, a GP and professor of primary care for older people at University College London, said the study was based on old estimates of dementia prevalence.
He said: ‘The authors of the report have used Alzheimer’s Society estimates from six years ago, and the situation is different now. My guess is that two-thirds to three-quarters of people with Alzheimer’s disease are known, and that under-diagnosis occurs more often with vascular dementia.
‘Then there is the tendency to describe some people with dementia as “mixed type” with Alzheimer’s features, and of course some individuals with apparent Lewy body dementia also receive cholinesterase inhibitors.’
The HSCIC report states there are ‘difficulties in producing robust estimates of expected numbers of patients at a sub-national level.’
It also says: ‘In interpreting these figures it is important to note that predicted and observed use may differ for a variety of reasons and they should not be assumed to definitely indicate either ‘under’ or ‘over’ prescribing. Clinical judgement, changes in prevalence or incidence, the time taken for the population to present to services to enable changes in prescribing, and demographic differences across healthcare economies are potential explanations for variations in results.’
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