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AlzRisk Risk Factor Literature Search Strategy and Results
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Risk Factor: Dietary Pattern
Risk Factor Type: Nutrition and supplements
Current Understanding:
Current Understanding The studies reviewed here generally provide support for an inverse relation between Alzheimer's disease and a healthy dietary pattern, defined loosely as a diet high in fruits and vegetables, low in red and processed meats, and favoring mono- and polyunsaturated fats over saturated fats. Although the studies varied somewhat in their definitions of healthy dietary pattern and used different methods to quantify adherence to that pattern, results were largely consistent. However, these studies have several methodological limitations that complicate their interpretation. Some studies adjusted for putative confounders like diabetes and cardiovascular disease that may in fact be causal intermediates, although effect estimates were similar with and without adjustment for these factors. No studies measured long-term dietary pattern and few measured dietary intake in mid-life, which are likely to be both more biologically relevant and less susceptible to reverse causation. Additional prospective studies addressing these limitations and evidence from randomized trials will help clarify the issue. In the meantime, a healthy dietary pattern, recommended for lowering risk of cardiovascular disease, may also lower risk of AD, particularly as part of a broader intervention including adequate physical activity and other lifestyle changes. For a review of the putative mechanisms by which dietary pattern may influence AD risk and detailed commentary on interpreting the findings below in a broader context, please view the Discussion.
Last Search Completed: 28 November 2016

Risk Factor Overview


Summary

We searched Pubmed for peer-reviewed articles reporting on the association between dietary patterns and Alzheimer’s disease (AD) incidence in cohort or nested case-control studies. The search returned 5,146 unique citations that, after title and abstract review against our inclusion criteria, were narrowed down to 36 citations for full-text review (all published in English). Of these, 11 fully met criteria for inclusion in our summary tables. We additionally excluded 3 articles that otherwise met our inclusion criteria, but duplicated an analysis from a cohort that contributed data to another included article. We reviewed these duplicate articles on a case-by-case basis, and selected the most informative article based on sample size, follow-up time, exposure assessment or modeling, and appropriateness of analytic methods. Please see our methods section for more detail on our general systematic review methods.

We ran an update of the search in Pubmed covering articles published between June 23, 2014 and November 28, 2016, which returned 1150 new citations. We excluded 1142 citations that did not meet our inclusion criteria (e.g. topic not appropriate, review or editorial, animal studies). Six studies were excluded after full text review because they did not meet inclusion criteria. Two articles were added to our Alzrisk tables from this updated search.

Search & Review Flowchart
Search Strategy
Selection of Papers Reporting on Data from the Same Cohort



Search Strategy Flowchart


Search Strategy

Using our systematic review methods, we developed a search strategy (table below) for Pubmed.


Search Strategy Table


Selection of Papers Reporting on Data from the Same Cohort

Some cohort studies produced multiple articles reporting on the association between dietary patterns and risk for Alzheimer’s disease. To avoid presenting duplicate results, we reviewed such articles on a case-by-case basis and selected the most informative article(s) based on sample size, follow-up time, exposure assessment or modeling, and appropriateness of analytic methods.

For each cohort listed below, we cite the duplicative articles we reviewed and give our rationale for their inclusion or exclusion. The full citation for each article is provided in the reference section.

Washington Heights-Inwood Columbia Aging Project (WHICAP)

We included main results from Scarmeas 2006 (Ann Neurol) and Gu 2010 (Arch Neurol). Each study used different methods to quantify adherence to a healthy dietary pattern (Mediterranean diet score and reduced rank regression). Scarmeas 2006 (Arch Neurol), Scarmeas 2009, and Gu 2010 (J Alzheimers Dis) used the same methods to quantify adherence to a healthy dietary pattern but reported findings in a subset of the population.

References

Scarmeas N, Stern Y, Tang MX, Mayeux R, Luchsinger JA. Mediterranean diet and risk for Alzheimer's disease. Ann Neurol. 2006 Jun;59(6):912-21.

Scarmeas N, Stern Y, Mayeux R, Luchsinger JA. Mediterranean diet, Alzheimer disease, and vascular mediation. Arch Neurol. 2006 Dec;63(12):1709-17. Epub 2006 Oct 9.

Scarmeas N, Luchsinger JA, Schupf N, Brickman AM, Cosentino S, Tang MX, Stern Y. Physical activity, diet, and risk of Alzheimer disease. JAMA. 2009 Aug 12;302(6):627-37.

Gu Y, Luchsinger JA, Stern Y, Scarmeas N. Mediterranean diet, inflammatory and metabolic biomarkers, and risk of Alzheimer's disease. J Alzheimers Dis. 2010;22(2):483-92.

Gu Y, Nieves JW, Stern Y, Luchsinger JA, Scarmeas N. Food combination and Alzheimer disease risk: a protective diet. Arch Neurol. 2010 Jun;67(6):699-706. Epub 2010 Apr 12.