Cognitive assessment is not improved by lifestyle interventions in diabetes. Health is.
After 10 years of intensive lifestyle intervention for overweight adults with type 2 diabetes mellitus, participants demonstrated better general and physical health than those without the intervention, but no better cognitive assessment scores, according to the latest report from the Action for Health in Diabetes (Look AHEAD) trial.
In addition to a lack of association of cognitive function with improvement in weight, fitness or glycemic control, the researchers reported a modest trend of harm to cognitive functioning among those receiving the intervention who had greater body mass index () and history of cardiovascular disease.
"The results...highlight the adverse cognitive consequences of diabetes mellitus and associated comorbidities and indicate the importance of understanding the mechanisms by which cognition is adversely affected, and of developing preventive and treatment interventions", observed Stephen Rapp, PhD, Professor, Psychiatry and Behavioral Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina and colleagues.
From over 5,000 volunteers who enrolled in Look AHEAD from 2001 to 2004, 3,751 received cognitive assessments at baseline and after 10 years randomization to either the intensive lifestyle intervention (ILI) or to customary diabetes support and education. The ILI participants were assigned dietary and physical activity goals for weight loss, with frequent follow-up in group or individual sessions.
Relative to those receiving customary support and education, the participants achieved and maintained significantly greater weight loss, better fitness, better glycemic control or a remission of diabetes, and attenuation of known cardiovascular risk factors.
The researchers noted that the lack of difference in cognitive measures between the groups was consistent with their earlier report of a subset of 978 participants assessed eight to nine years after randomization and two to three years after both treatments were stopped. It was also consistent with cited studies of lifestyle intervention in patients with pre-diabetes. In the Finnish Diabetes Prevention Study, a similar intervention program was not associated with better cognition 12 years after randomization, although poorer glycemic control was related to worse cognition.
Rapp and colleagues point to other evidence, however, that would suggest that the ILI could have improved cognitive functioning, including associations of midlife obesity with long-term risk of dementia and cognitive decline in later life. In addition, the population studied here, obese and over-weight individuals with type 2 diabetes, have been identified as being at high risk of cerebrovascular disease, brain atrophy, and declining brain function with corresponding cognitive deficits and dementia.
The researchers offer one possibility of finding future cognitive benefit from the ILI intervention, in the "legacy effect", referring to the lag time that can occur between an intervention affecting metabolic processes and realization of clinical benefits. They point out that in the U.K. Prospective Diabetes Study comparison of intensive glycemic control with treatment as usual, improvement in microvascular but not macrovascular outcomes was observed at completion of treatment, while macrovascular improvements emerged only after 10 years of follow-up.
The study was published on-line January 9 in the Journal of the American Geriatrics Society. Effect of a Long-Term Intensive Lifestyle Intervention on Cognitive Function: Action for Health in Diabetes Study