Blood pressure forced too low and cognitive impairment

Blood pressure treatment should relieve hypertension without attempting to achieve 'perfect' levels which can harm by impairing brain perfusion resulting in cognitive impairment. A study just published JAMA Internal Medicine adds to the body of evidence indicating that blood pressure management in the elderly must allow adequate pressure to maintain circulation to the periphery (which includes the brain). The authors set out to...

"...assess whether office blood pressure, ambulatory blood pressure monitoring, or the use of antihypertensive drugs (AHDs) predict the progression of cognitive decline in patients with overt dementia and mild cognitive impairment (MCI)."

Daytime systolic blood pressure equal or less than 128 mm Hg

They analyzed data for 172 patients whose average age was 79 with a Mini-Mental State Examination (MMSE) mean score of 22.1, among whom 68% had dementia, 32% had mild cognitive impairment (MCI), and 69.8% were being treated with anti-hypertensive drugs (AHDs). Over-medicating for blood pressure was associated with cognitive impairment:

"Patients in the lowest tertile of daytime systolic blood pressure (SBP) (≤128 mm Hg) showed a greater MMSE score change compared with patients in the intermediate tertile (129-144 mm Hg) and patients in the highest tertile (≥145 mm Hg). The association was significant in the dementia and MCI subgroups only among patients treated with AHDs. In a multivariable model that included age, baseline MMSE score, and vascular comorbidity score, the interaction term between low daytime SBP tertile and AHD treatment was independently associated with a greater cognitive decline in both subgroups. The association between office SBP and MMSE score change was weaker. Other ambulatory blood pressure monitoring variables were not associated with MMSE score change."

Lower is not always better

The authors of a commentary in the same issue of JAMA Internal Medicine write:

"We think it is time to move from the concept of 'the lower the better' to the concept of 'hemodynamic optimization' to decelerate the pace of cognitive decline by a proper management of blood pressure."

Evidence-based guideline from the Eighth Joint National Committee (JNC 8) 2014

Recommendations from these guidelines as listed in Medscape include:

• In patients aged 60 years or older, start treatment for SBP >150 mm Hg or DBP >90 mm Hg and treat to under those thresholds.
• In patients aged 18-60 years, treatment initiation and goals should be 140/90 mm Hg.
• The same goals apply to patients with diabetes or CKD.
• In nonblack patients, initial treatment can be a thiazide-type diuretic, calcium channel blocker (CCB), angiotensin-converting-enzyme (ACE) inhibitor, or angiotensin receptor blocker (ARB).
• For black patients, initial therapy should be a thiazide-type diuretic or CCB.
• In patients aged 18 years or older with CKD, initial or add-on therapy should be an ACE inhibitor or ARB, regardless of race or diabetes status.

The authors of the study on blood pressure treatment and cognitive impairment conclude:

"Low daytime SBP was independently associated with a greater progression of cognitive decline in older patients with dementia and MCI among those treated with AHDs. Excessive SBP lowering may be harmful for older patients with cognitive impairment. Ambulatory blood pressure monitoring can be useful to help avoid high blood pressure overtreatment in this population."