A new study by French and UK researchers published in a leading journal this week suggests that should no cure be found for dementia, then the biggest impact on reducing rates of this progressive brain destroying disease is likely to come from eliminating diabetes and depression and boosting education, as well as encouraging people to eat more fruit and vegetables.

These findings coinicide with those of another paper that suggests GPs in the UK need to get better at detecting dementia earlier.

You can read about both studies, and an accompanying editorial, online in the 5 August issue of the BMJ.

Dementia is the largest cause of disability in industrialized societies: it is progressive and people gradually lose the ability to take care of themselves and carry out every day tasks of living.

Although we don’t know what causes dementia, scientists have identified several modifiable risk factors aside from the APOE gene. These include a history of depression, alcohol, education, diet, and a cluster called vascular risk factors because they affect the blood supply in the brain, such as stroke, heart disease, high blood pressure, high cholesterol, diabetes and obesity.

Taking this as the starting point, researchers from public research body INSERM and the University of Montpellier in France and from Imperial College in London, estimated the impact eliminating these risk factors (they included the genetic one for reference) might make on reducing rates of dementia, should no effective treatment be found.

For their investigation, they analyzed data on 1,433 healthy individuals living in Montpellier in the south of France, who were aged 65 years and over and whose average age was 72.5 years when recruited between 1999 and 2001.

The participants underwent cognitive tests at the start of the study and then two, four and seven years later. They also took a reading test that yielded a Neale score as a measure of lifetime intelligence and a test that assessed their genetic risk, which the researchers used as a benchmark.

The researchers also had information on each participant’s medical history, height, weight, level of education, income, mobility, diet, alcohol and smoking habits.

From their analysis they estimated that over the next seven years, among the general population:

  • Eliminating depression and diabetes and eating more fruit and vegetables would reduce new cases of dementia by 21 per cent.
  • The greatest impact would be from eliminating depression (just over 10 per cent reduction, although there is no evidence that it actually causes dementia, they noted).
  • Increasing education would lead to an 18 per cent reduction in new cases of dementia.
  • In contrast to these modifiable risk factors, eliminating the genetic risk would only reduce new cases by 7 per cent.

The researchers concluded that education and fruit and vegetable consumption and eliminating depression and diabetes are likely to have the biggest impact on reducing new cases of dementia.

While these are only crude estimates, they make a strong statement about public health priorities, and the potential they have to make a difference that surpasses the effect of removing the known genetic risk.

The researchers suggest public health initiatives should concentrate on increasing literacy of people at all stages of life, irrespective of ability, earlier diagnosis and treatment of depression, and screening for early signs of diabetes.

They also recommend that further studies be done to test the impact of interventions, and these should also include younger adults.

In the second paper, researchers from the UK’s Medical Research Council (MRC) and University College London (UCL), suggest that earlier and better detection of dementia in primary care is needed.

They found that “median survival was much lower than in screened populations”, and death rates in the first year after diagnosis were more than three times higher in people with dementia and that this was probably because diagnosis did not happen until a crisis occured in the late stages of the disease.

“Late recording of diagnoses of dementia in primary care may result in missed opportunities for potential early interventions,” they concluded.

In an accompanying editorial, Dr Elizabeth England, an NIHR clinical research fellow in the Department of Primary Care Clinical Sciences at the University of Birmingham in the UK, said that public health should focus on better education and training of GPs and other primary care practitioners, develop more integrated care, and make sure primary care policies and services put more emphasis on dementia.

“Designing prevention programmes to reduce incidence of dementia: prospective cohort study of modifiable risk factors.”
K Ritchie, I Carrière, C W Ritchie, C Berr, S Artero, M-L Ancelin.
BMJ 2010;341:c3885
DOI: 10.1136/bmj.c3885 (Published online 5 August 2010)

“Survival of people with clinical diagnosis of dementia in primary care: cohort study.”
Greta Rait, Kate Walters, Christian Bottomley, Irene Petersen, Steve Iliffe, Irwin Nazareth.
BMJ 2010;341:c3584
DOI: 10.1136/bmj.c3584 (Published online 5 August 2010)

Additional source: BMJ Press Release.

Written by: Catharine Paddock, PhD