Lower blood pressure, BMI may precede dementia

Low blood pressure (BP) and weight loss could signal an impending diagnosis of dementia, while elevated blood glucose levels may represent a consistent risk factor for the condition, according to a 14-year study published in the October issue of JAMA Psychiatry.

“To our knowledge, no large cohort study has concurrently examined the trajectories of all main cardiovascular risk factors in the years preceding dementia diagnosis, and the optimal targets and time windows in older ages for the management of cardiometabolic health for dementia prevention have remained unclear,” wrote lead author Maude Wagner, MPH, from the University of Bordeaux, and colleagues.

To address this research gap, Wagner et al. took 785 patients who ultimately developed dementia from a French population-based cohort study and matched each of them to four non-dementia controls (3,140 people total) based on age, sex, educational attainment and the center at which they were diagnosed. Overall, the study population was 76 years old on average at baseline and 65 percent women.

The researchers then analyzed several cardiometabolic risk factors captured during a series of follow-up visits out to 14 years, noting the differences in those measurements between dementia cases and non-dementia controls. In general, cases showed a faster decline in body mass index (BMI), a slower increase in systolic BP (SBP), constantly lower diastolic BP (DBP) and consistently elevated blood glucose levels.

The average changes in each measurement from 14 years pre-diagnosis to the time of diagnosis were as follows:

  • BMI—26.1 to 24.8 in cases, 25.7 to 25.3 in controls.
  • SBP—135.2 to 142.1 in cases, 135.8 to 144.9 in controls.
  • DBP—76.5 to 74.0 in cases, 76.7 to 75.0 in controls.
  • Fasting glucose levels—89.4 to 96.4 mg/dL in cases, 87.1 to 95.3 mg/dL in controls. A statistically significant difference between cases and controls was noted from 1.6 years prediagnosis all the way to 14 years before diagnosis.
  • There were no significant differences between groups in the trajectories of blood lipid levels, including HDL cholesterol, LDL cholesterol and triglycerides.

“In this large cohort of older persons, BMI declined in prodromal dementia, possibly reflecting early preclinical changes,” the authors wrote. “Lower BP prior to dementia may reflect both a consequence and a contributing factor for the disease, whereas higher blood glucose levels may constitute a risk factor for dementia in the older age range.

“Overall, these findings suggest that elevated glycemia, low BP, and weight loss may be primary targets for the management of cardiometabolic health for primary and secondary prevention of dementia.”

Wagner and colleagues noted the decline in BMI became steeper in the dementia group up to seven years before diagnosis.

“The decline of BMI and HDL-C found with general aging in this cohort and in previous studies may reflect weight loss and malnutrition associated with the loss of muscle mass, appetite, and olfactory function in older persons,” they wrote. “Likewise, the increase of SBP and decrease of DBP may be a consequence of age-related development of large-artery stiffness and atherosclerosis.”

The researchers noted their follow-up period began in late life, so the results may not inform dementia prevention targets beginning in midlife or earlier. Also, most of the study participants were urban French residents, so the generalizability to populations from different backgrounds is unknown.