BETHESDA, MD. — Current knowledge about the epidemiology of Alzheimer's disease and cognitive decline has not provided enough evidence to recommend specific, preventive interventions, according to a draft “state-of-the-science” report issued by a panel of experts assembled by the National Institutes of Health.
The 15-member panel found that there is not enough clinical evidence to support the use of pharmaceutical agents or dietary supplements to prevent cognitive decline or Alzheimer's disease, but ongoing additional studies of antihypertensive medications, omega-3 fatty acids, physical activity, and cognitive engagement “may provide new insight into the prevention of delay of cognitive decline or Alzheimer's disease.”
“We're hoping that our report is going to supply physicians with accurate information that they can give to their patients” to clarify what interventions may be worth continuing or pursuing and which should be discontinued, panelist Dr. Carl C. Bell, director of the Institute for Juvenile Research in the department of psychiatry at the University of Illinois at Chicago, said at a press telebriefing.
A wide range of modifiable factors has been reported to be associated with risk for Alzheimer's disease, such as diabetes, elevated blood cholesterol in midlife, and depression, but also relatively benign changes in diet, medication, or lifestyle.
However, the overall quality of evidence from these studies is low, the panel said, and they did not find enough evidence to draw firm conclusions about the association of modifiable risk factors with cognitive decline or Alzheimer's disease.
In light of the fact that there are no proven interventions that prevent cognitive decline or Alzheimer's disease, panel member Arnold L. Potosky, Ph.D., of Georgetown University in Washington said that it is important for physicians to discuss participation in clinical studies with their patients.
The panel recommended that further research should include:
▸ The development and use of rigorous, consensus-based diagnostic criteria for Alzheimer's disease and mild cognitive impairment.
▸ The development and use of a standardized, well-validated, and culturally sensitive battery of outcome measures across research studies.
▸ The collection of data from caregivers of people with mild cognitive impairment or early Alzheimer's disease in a systematic manner in observational studies and randomized, controlled trials.
▸ The conduct of large-scale, long-term population-based studies with well-validated exposure and outcome measures in people followed from middle to old age. Existing cohorts from ongoing studies of this type also could be explored for timely, cost-effective identification of individuals at high risk of cognitive decline or Alzheimer's disease.
▸ The leveraging of alternative research resources and platforms that facilitate long-term longitudinal assessments, such as a multicenter Alzheimer's disease registry or observational studies within large health care delivery systems with defined populations and well-developed electronic health records.
▸ The creation of a simple, inexpensive, quantitative instrument that can be administered by a trained nonexpert to assess change in cognitive status over time.
The scope of the statement was restricted to studies of people aged 50 years or older that were conducted in developed countries. The minimum sample size in these studied was at least 50 patients in randomized, controlled trials and at least 300 patients in observational studies.
The duration between exposure to a preventive intervention and study outcomes had to be at least 1 year for studies of mild cognitive impairment and at least 2 years for studies of Alzheimer's disease.
The panel based their draft statement on an evidence report from the Evidence-Based Practice Center at Duke University's Clinical Research Institute, which was commissioned by the Agency for Healthcare Research and Quality.
The evidence report is available at www.ahrq.gov/clinic/tp/alzcogtp.htmconsensus.nih.gov
The report should clarify what interventions may be worth continuing and which should be discontinued.
Source DR. BELL