Blood pressure and brain volumes: lower is not always better: the ages-reykjavik study
Majon Muller,1,2 Thor Aspelund,2 Sigurdur Sigurdsson,3 Palmi V. Jonnson,3 Mark van Buchem,4 Vilmundur Gudnason,3 Lenore J. Launer1
1 National Institute on Aging; 2VU University Medical Center Amsterdam, The Netherlands; 3The Icelandic Heart Association, Iceland and 4Leiden Univeristy Medical Center, The Netherlands.
Background: Midlife hypertension increases risk for brain pathology later in life. The effects of late-life BP on brain pathology is less consistent, with some studies even showing that low BP has detrimental effects on the brain. An explanation for these conflicting findings could be that chronic hypertension causes cerebrovascular pathology, making the brain more vulnerable for hypoperfusion and possibly low BP levels. We therefore hypothesize that in subjects with hypertension since midlife, lower late-life BP levels will lead to more brain pathology.
Methods: Within the AGES-Reykjavik study (2002-06), a population-based study, analyses were performed in 4306 non-demented older individuals (mean age 76±5 years) with data on vascular risk and brain volumes on MRI. Total brain (TB) volume was calculated by summing the gray matter (GM), white matter (WM), and white matter lesion (WML) volumes. Mid-life assessment of vascular factors was conducted between 1967–96. Hypertension was defined as BP ≥140/90 mm Hg and/or use of antihypertensives.
Results: Regression analyses adjusted for age, sex, intracranial volume, vascular risk, WML, and brain infarcts showed that the association of late-life diastolic BP (DBP), but not systolic BP (SBP), with TB and GM was modified by midlife hypertension status (P-interaction<0.01). In subjects with midlife hypertension (n=1464), but not in those without midlife hypertension, lower late-life DBP was associated with smaller TB and GM volumes (Figure 1). No interaction between midlife hypertension and late-life BP on WM was observed, but higher BP was related with smaller WM volume.
Conclusion: Midlife hypertension in combination with lower late-life BP is associated with smaller brain volumes. These findings provide evidence of a cumulative effect of early hyper- and late hypo-perfusion that leads to certain subgroups in old age with increased susceptibility to brain atrophy.
Keywords: Hypertension; Blood Pressure; Brain Atrophy