BMI, Blood Pressure, Glycemia Linked to Dementia

Keith Fargo, PhD

A 14-year case-control study of older adults reports that elevated blood glucose was the only cardiometabolic risk factor with consistently higher values among participants with future dementia up to 14 years before diagnosis. The study was presented at the Alzheimer's Association International Conference on July 24, 2018 in Chicago, Illinois.

The study noted that in cases, body mass index (BMI) declined and systolic blood pressure (BP) increased more slowly in the 14 years before diagnosis, compared to controls. Study authors, led by Maude Wagner, MPH, Bordeaux Population Health Research Center, University of Bordeaux, suggested that the lower BP in prodromal dementia could be a “consequence and a contributing factor” while higher blood glucose levels may be a risk factor for dementia among older adults.

“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 in the older age range,” said Wagner et al.

This study is nested within an ongoing, prospective cohort study of adults aged 65 and older, the Three-City (3C) study, that began in 1999. The present study matched dementia cases (n = 841) with 4 controls each and compared the trajectories for major cardiometabolic risk factors up to 14 years preceding dementia diagnoses for the cases.

Specifically, the researchers examined BMI, systolic BP, diastolic BP, HDL cholesterol, LDL cholesterol, triglycerides, and glycemia levels between 1999 and 2014. Measurements were taken at baseline (T₀) and at 5 follow up visits to participants in Dijon every 2-3 years (T₂, T₄, T₇, T₁₀, T₁₂) and 6 visits to participants in Bordeaux and Montpellier (including the additional T₁₄).

Of the 841 cases, 785 (93.3%) were successfully matched to 4 controls, leading to a nested case-control sample of 3925 participants. The authors found that cases

• Average BMI: 26.1 at 14 years prior and 24.8 at diagnosis for a case with dementia compared to 25.7 at 14 years prior and 25.3 at diagnosis for a dementia-free control.
• Systolic BP: 135.2 mm Hg at 14 years prior and 142.1 mm Hg at diagnosis for a case compared to 135.8 mm Hg at 14 years prior and 144.9 mm Hg at diagnosis for a control.

“We are learning that cardiovascular risk factors affect dementia risk substantially, and importantly that these risk factors may have implications in midlife or even before for later dementia risk,” Keith Fargo, PhD, Director of Scientific Programs at the Alzheimer’s Association, told MD Magazine®. “Close monitoring and appropriate control of these risk factors may substantially reduce a person's risk for later life cognitive impairment.”

Another study presented at the Alzheimer’s Association International Conference, the SPRINT-MIND trial, looked at the effect of targeting hypertension on mild cognitive impairment (MCI) and dementia.

In that study, participants with hypertension and increased cardiovascular risk were randomized to either an intensive strategy arm with a systolic blood pressure goal of <120 mm Hg or a standard care strategy arm with a systolic blood pressure goal of <140 mm Hg (135 to 139 mm Hg).

The SPRINT-MIND study showed that rates of MCI were 19% lower among participants in the intensive hypertension control arm and the combined outcome of MCI plus probable all-cause dementia was 15% lower for that study arm.

Fargo explained that these results are not contradictory, but that the early stages of dementia may influence certain measurements, including BMI and blood pressure.

“When a person is in the incipient stages of dementia, even a decade or more before a clinical diagnosis can be made, BMI and blood pressure may be reduced compared to people of a similar age who are not in the prodromal stages of dementia,” said Fargo. “However, BMI and high blood pressure are both also well-established risk factors for cognitive impairment later in life, and the SPRINT-MIND clinical trial showed that targeting a systolic blood pressure of 120 mmHg lowered risk of cognitive impairment by 15 to 20%.”

Looking forward, Fargo highlighted the US POINTER study, a large clinical trial of “multi-component lifestyle intervention,” which will begin enrolling participants later this year.

“The clinical trial includes exercise, diet, social and cognitive stimulation, and close monitoring and control of cardiovascular risk factors such as blood pressure and blood sugar levels,” Fargo told MD Mag.

The study, “Evaluation of the Concurrent Trajectories of Cardiometabolic Risk Factors in the 14 Years Before Dementia,” was presented at the Alzheimer's Association International Conference on July 24, 2018 in Chicago, Illinois and published in JAMA Psychiatry.