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Epidemiology:
doi: 10.1097/EDE.0b013e31823b6513
Letters

Hypertension and Alzheimer Disease: Is There a Link?

Power, Melinda C.; Weuve, Jennifer; Gagne, Joshua J.; McQueen, Matthew B.; Viswanathan, Anand; Blacker, Deborah

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Department of Epidemiology Harvard School of Public Health Boston, MA Department of Environmental Health Harvard School of Public Health Boston, MA mcpower@hsph.harvard.edu (Power)

Department of Environmental Health Harvard School of Public Health Boston, MA Institute for Healthy Aging and Department of Internal Medicine Rush University Medical Center Chicago, IL (Weuve)

Department of Epidemiology Harvard School of Public Health Boston, MA Division of Pharmacoepidemiology and Pharmacoeconomics Brigham and Women's Hospital and Harvard Medical School Boston, MA (Gagne)

Department of Psychology and Institute for Behavioral Genetics University of Colorado Boulder, CO (McQueen)

Hemorrhagic Stroke Research Program Department of Neurology Massachusetts General Hospital Harvard Medical School Boston, MA (Viswanathan)

Department of Epidemiology Harvard School of Public Health Boston, MA Gerontology Research Unit Department of Psychiatry Massachusetts General Hospital Harvard Medical School Boston, MA (Blacker)

Supported by a grant from an anonymous foundation. M.C.P is supported by a National Institute of Aging training grant (T32 ES007069). The authors reported no other financial interests related to this research.

The authors respond:

We are grateful for the careful attention Drs. Steenland, Levey, and Goldstein1 have given to our review2 of the association between blood pressure and incident Alzheimer disease. We share many of their concerns (as we discuss in our paper) and their recommendations for future research. We also agree that we cannot, based on the current epidemiologic research, draw firm conclusions about the presence or absence of an association.

As their letter highlights, misclassification of blood pressure is a concern and may obscure a true effect if one is indeed present. As we state in our review, misclassification of blood pressure “might contribute to the overall null findings, although it is unlikely to account for the suggestion of either an adverse association between midlife blood pressure and Alzheimer disease or an inverse association between late-life blood pressure and Alzheimer disease.” We will be interested to see how this understanding changes when information on hypertension duration, severity, and treatment (and its efficacy) are incorporated into epidemiologic studies of the relationship between blood pressure and Alzheimer disease.

Systematic review and meta-analysis are powerful tools. However, static summaries, including our recent report,2 are limited in several ways. They provide a snapshot of the literature at a single point in time, and thus cannot incorporate new findings. In addition, the journal-article format precludes easy access to details about the individual studies included in a systematic review, such as those highlighted by Steenland and colleagues. Online compendia, such as the AlzRisk website (www.alzrisk.org; hosted by the Alzheimer Research Forum), overcome these limitations. The AlzRisk entry on blood pressure (http://www.alzrisk.org/riskfactorview.aspx?rfid=1), completed in parallel with our paper, offers additional details on each study, and will be updated as new research is published.

Overall, the perceived causal link between blood pressure and Alzheimer disease is currently supported more strongly by theory and indirect evidence than by solid epidemiologic data.

Melinda C. Power

Department of Epidemiology

Harvard School of Public Health

Boston, MA

Department of Environmental Health

Harvard School of Public Health

Boston, MA

mcpower@hsph.harvard.edu

Jennifer Weuve

Department of Environmental Health

Harvard School of Public Health

Boston, MA Institute for Healthy Aging and Department of Internal Medicine

Rush University Medical Center

Chicago, IL

Joshua J. Gagne

Department of Epidemiology

Harvard School of Public Health

Boston, MA

Division of Pharmacoepidemiology and Pharmacoeconomics

Brigham and Women's Hospital and Harvard Medical School

Boston, MA

Matthew B. McQueen

Department of Psychology and Institute for Behavioral Genetics

University of Colorado

Boulder, CO

Anand Viswanathan

Hemorrhagic Stroke Research Program

Department of Neurology

Massachusetts General Hospital

Harvard Medical School

Boston, MA

Deborah Blacker

Department of Epidemiology

Harvard School of Public Health

Boston, MA

Gerontology Research Unit

Department of Psychiatry

Massachusetts General Hospital

Harvard Medical School

Boston, MA

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REFERENCES

1. Steenland NK, Levey AI, Goldstein. Hypertension and Alzheimer disease [letter]. Epidemiology. 2012;23;176–177.

2. Power MC, Weuve J, Gagne JJ, McQueen M, Viswanathan A, Blacker D. The association between blood pressure and incident Alzheimer disease: a systematic review and meta-analysis. Epidemiology. 2011;22:646–659.

© 2012 Lippincott Williams & Wilkins, Inc.

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