Aug 22, 2009
Smoking, high blood pressure, and diabetes may lead to dementia
August 20, 2009 | Allison Gandey
Adapted from Medscape Medical News—a professional news service of WebMD
London, UK - Middle-aged people who smoke or have high blood pressure or diabetes are more likely to develop dementia later in life, according to a new study . In an article published online August 19, 2009 in the Journal of Neurology, Neurosurgery and Psychiatry, researchers suggest that controlling cardiovascular risk factors in midlife may prevent dementia later on.
"Our study population included both whites and African Americans," said lead author Dr Alvaro Alonso (University of Minnesota, Minneapolis). "We were able, for the first time, to show that cardiovascular risk factors in midlife are associated with dementia later in life in both racial and ethnic groups."
Overall, blacks had a 2.5 times higher rate of hospitalization for dementia than whites. Black women 75 years and older had the highest rates of all.
Predictors more predictive at younger ages
Current smokers were 70% more likely than those who had never smoked to develop dementia. People with high blood pressure were 60% more likely than those without high blood pressure to develop dementia, and people with diabetes were more than twice as likely as those without diabetes to experience cognitive impairment.
The researchers also demonstrated that cardiovascular risk factors measured earlier in life are better predictors of dementia than risk factors measured in older age. "These results, again, support the need for paying special attention to cardiovascular risk factors in midlife," Alonso said.
Investigators studied more than 11 000 people who were part of the Atherosclerosis Risk in Communities (ARIC) study. Participants were aged 46 to 70 years and underwent a physical examination and cognitive testing. Patients were followed up for more than a decade to see how many would later develop dementia.
Researchers identified 203 patients hospitalized with dementia. Smoking, high blood pressure, and diabetes were all strongly associated with this diagnosis.
In analyses including updated information on risk factors during follow-up, the hazard ratio of dementia in hypertensive vs nonhypertensive participants was 1.8 at age <55 compared with 1.0 at age 70 or older. Researchers observed similar results for diabetes, with a hazard ratio of 3.4 at age <55 and 2.0 in those older than 70. For smoking, the hazard ratio was 4.8 at age <55 and 0.5 in patients aged 70 or older.
"We were able to identify only individuals with dementia who were attended in a hospital," Alonso pointed out. "Therefore, it is very likely that we missed some people with dementia. Still, we did a number of additional analyses to determine whether this could bias our results. Overall, we are confident that this limitation is not having a major impact in our overall conclusions."
The authors point to another criticism that could explain the study results. "An unmeasured factor in our population could be associated with the presence of cardiovascular risk factors and also increase the risk of dementia," Alonso added. For example, a genetic marker that increases both the risk for hypertension and dementia could be at play. "This is a possibility," he said, "but in our analysis, we adjusted for the most important variables associated with cardiovascular risk factors and dementia, including some genetic factors such as apolipoprotein E."
Bad for the heart, bad for the brain
In the August 2009 issue of Dementia and Geriatric Cognitive Disorders, researchers came to a similar conclusion and reported that elevated cholesterol in midlife may increase dementia risk .
The authors, led by Dr Alina Solomon (University of Kuopio, Finland), followed 9844 patients over more than 40 years using data from the Kaiser Permanente Northern California Medical Group. During that time, 469 patients developed Alzheimer's disease and 127 developed vascular dementia.
The hazard ratio (HR) associated with total cholesterol of at least 240 mg/dL (compared with <200 mg/dL) for development of Alzheimer's was a significant 1.57 (95% CI 1.23-2.01) but for vascular dementia was a nonsignificant 1.26 (0.82-1.96). The vascular-disease HR was 1.50 (1.01-2.23) for total cholesterol 200 to 239 mg/dl.
In an analysis by total-cholesterol quartiles, the risk of developing Alzheimer's disease increased significantly when levels exceeded 220 mg/dL. "Both physicians and patients need to know that elevated cholesterol increases the risk not only for heart disease, but also for dementia," Solomon said.
Dr Robert Stewart (King's College London, UK), who isn't connected with the study, said in an interview that the data are convincing and consistent with those from other studies that have screened community populations for this disorder.
"In general," Stewart said, "there is now a large body of evidence that indicates that what is bad for the heart is bad for the brain—that is, that the well-known risk factors for coronary heart disease and stroke are also risk factors for dementia."