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TMR Integrative Nursing  2018, Vol. 2 Issue (3): 101-107    DOI: 10.12032/TMRIN20180709
Methodology assessment     
Methodologic quality of systematic reviews and meta-analyses on the Mediterranean diet and cognitive function: a review
Yuan Jia1, Si-Yuan Yang1, Li-Ming Guo1, Qian Wu1, Fan-Jie Meng2,*()
1Graduate College, Tianjin University of Traditional Chinese Medicine, Tianjin, China
2Teacher Evaluation and Development Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China.
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This article summarizes the systematic assessment and meta analysis of the impact of existing Mediterranean-style diets on cognitive function and evaluates the methodological quality, providing strong evidence for the development of related work and standardizing the research process and methods in this field.

Editor’s Summary

Systematic review has been the effective tool of summarizing the available best evidence; however, the quality of methodology is a positive association with the value of evidence which will be used to inform decision-making. Consequently, this article assesses the methodology of all available systematic reviews of investigated the role of Mediterranean diet in cognitive function.


Background and aim: Several systematic reviews and meta-analyses published within the past years have examined the associations of Mediterranean-style diets (MedSDs) on cognitive. However, these reviews have not been evaluated for satisfying Contemporary methodologies quality standards. At the same time, due to the high demand for related care during the aging process in China, it is necessary to summarize the ex-isting system evaluation and evaluate the quality of it, so as to provide strong evidence for the development of relevant work and to standardize the research process and methods in this field. This study evaluated the quality of recent systematic reviews and meta-analyses on MedSD and cognitive outcomes by using an established methodology quality scale, and to provide some valuable references for future research and Chinese systematic review and meta-analysis developing. Methods: We used the AMSTAR Methodology Quality Assessment Scale to evaluate the quality of methodology of the existing meta-analyses and systematic review. Meta analysis and systematic review that meets our criteria must contain the following characteristics: 1) used systematic or meta-analytic procedures to review the lit-erature, and 2) had MedSD interventions independently. Results: Reviews satisfied with 5 to 9 of the AMSTAR MedSD items (mean 7.35, standard deviation: 1.27), quality is above average with those published in higher-impact journals having a greater quality score. Conclusion: These data suggest that current meta-analyses/systematic reviews evaluating the effect of MedSD on cognitive do not fully meet contemporary methodology quality standards. The methodological quality of the literature needs to be improved. As a result, there are more research questions to answer to enhance our understanding of how MedSD affects cognitive. To clarify associations between MedSD and cognitive, future meta-analyses and systematic reviews should not only follow methodology quality standards but also include more statistical modeling results when data allow. And in order to make the conclusions more reliable, we expect higher quality RCTs in the future.

Key wordsCognitive      Mediterranean diet      Meta-analysis      Methodological quality      Systematic reviews     
Published: 24 September 2018
Corresponding Authors: Meng Fan-Jie     E-mail:
Cite this article:

Yuan Jia, Si-Yuan Yang, Li-Ming Guo, Qian Wu, Fan-Jie Meng. Methodologic quality of systematic reviews and meta-analyses on the Mediterranean diet and cognitive function: a review. TMR Integrative Nursing, 2018, 2(3): 101-107.

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Figure 1 Flow chart detailing search of potential systematic reviews and selection process of included reviews. CNKI, China National Knowledge Infrastructure.
First Author Publication year Country Number of included studies Outcome indicators
Wu L[29] 2017 China 9 a,b,d
Petersson SD[25] 2016 America 32 a,b,c
Psaltopoulou T[26] 2013 Greece 22 a,b,e,
Singh B[28] 2014 America 5 a,b
Radd-Vagenas S[27] 2018 Australia 5 a,b,c
Masana MF[24] 2017 Australia 31 a,b,c,d
Hardman RJ[21] 2016 Australia 18 a,b,c
Loughrey DG[22] 2017 Britain 17 a,b,c,d
Lourida I[23] 2013 Britain 12 a,b
Table 1 Summary of the 10 systematic reviews or meta-analyses that qualified for this review
AMSTAR question Yes Part No
1. Was an a priori design provided? . 9 0 1
2. Was a comprehensive literature search performed? 7 0 3
3. Is it possible to replicate the search? 8 0 2
4. Did the inclusion criteria permit gray literature? 3 1 6
5. Was a list of studies (included and excluded) provided? 0 0 10
6. Were the characteristics of the included studies provided? 8 1 1
7. Was the scientific quality of the included studiesassessed and documented? 7 0 3
8. Were the methods used to combine the findings of studies appropriate? 10 0 0
9. Was the effect size index chosen justified statistically? 8 1 1
10. Was the likelihood of publication bias assessed? 7 1 2
11. Was the conflict of interest included? 5 0 5
Table 2 Quality of systematic reviews and meta-analyses
1.   Prince M, Wimo A, Guerchet M, et al. World Alzheimer report 2015: the global impact of dementia: ananalysis of prevalence, incidence, costandtrends. London: Alzheimer’s Disease International 2015.
2.   Alzheimer’s Society Alzheimer’s Society online information - About dementia - What is dementia? Leading the fight against Dementia 2014.
3.   Harwood RH, Sayer AA, Hirschfeld M.Current and future worldwide prevalence of dependency, its relationship to total population, and dependency ratios. Bull World Health Organ 2004, 82: 251-258.
4.   Australian Institute of Health and Welfare. Dementiain Australia. Cat. no. AGE70. Canberra, Australia: AIHW; 2012.
5.   Buckley JS, Salpeter SR.A risk-benefit assessment of dementia medications: systematic review of thee vidence. Drugs Aging 2015, 32: 453-467.
doi: 10.1007/s40266-015-0266-9 pmid: 25941104
6.   Craig JV, Bunn DK, Hayhoe RP, et al. Relationship between the Mediterranean dietary pattern and musculoskeletal health in children, adolescents, and adults: systematic review and evidence map. Nutr Rev 2017, 75: 830-857.
7.   Forsyth C, Kouvari M, D'Cunha NM, et al. The effects of the Mediterranean diet onrheumatoid arthritis prevention and treatment: a systematic review of human prospective studies. Rheumatol Int 2017, 38: 737-747.
8.   Godos J, Zappalà G, Bernardini S, et al. Adherence to the Mediterranean diet is inversely associated with metabolic syndrome occurrence: a meta-analysis of obser-vational studies. Int J Food Sci Nutr 2017, 68: 138-148.
9.   Huedo-Medina TB, Garcia M, Bihuniak JD, et al. Methodologic quality of meta-analyses and systematic reviews on the Mediterranean diet and cardiovascular disease outcomes: a review. Am J Clin Nutr 2016, 103: 841-850.
10.   Park J, Kim J.Meta analysis of relation between mediterranean diet and overall mortality. Atherosclerosis 2015, 241: e195.
doi: 10.1016/j.atherosclerosis.2015.04.949
11.   Tyrovolas S, Panagiotakos DB.The role of Mediterranean type of diet on the development of cancer and cardiovascular disease, in the elderly: a systematic review. Maturitas 2010, 65: 122-130.
12.   Weed DL, Althuis MEDSD, Mink PJ.Quality of reviews on sugar-sweetened beverages and health outcomes: a systematic review. Am J Clin Nutr 2011, 94: 1340-1347
13.   Sofi F, Cesari F, Abbate R, et al. Adherence to Mediterranean diet and health status: meta-analysis. BMJ 2008, 337: a1344.
doi: 10.1136/bmj.a1344 pmid: 18786971
14.   Trichopoulou A, Costacou T, Bamia C, et al. Adherence to a Mediterranean diet and survival in a Greek population. N Engl J Med 2003, 348: 2599-2608.
doi: 10.1056/NEJMoa025039 pmid: 12826634
15.   Anonymous Mediterranean Diet Pyramid. Oldways: health through heritage. Mediterranean diet pyramid 2015. Available from:. Oldways: health through heritage. Mediterranean diet pyramid 2015. Available from:.
16.   Estruch R, Ros E, Salas-Salvado J, et al. Primary prevention of cardiovascular dis-ease with a Mediterranean diet. N Engl J Med 2013, 368: 1279-1290.
17.   USDA,Center for Nutrition Policy and Promotion. Report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans, 2015. Washington (DC): Office of Disease Prevention and Health Promotion 2015.
18.   Fitó M, Guxens M, Corella D, et al. Effect of atraditional Mediterranean diet on lipoprotein oxidation: a randomized controlledtrial. Washington(DC): Office of Disease Prevention and Health Promotion. Arch Intern Med 2007, 167: 1195-1203.
19.   Shea BJ, Grimshaw JM, Wells GA, et al. Development of AMSTAR: a measurementtool to assess the methodological quality of systematic reviews. BMC Med Res Methodol 2007, 7: 10.
20.   Aridi YS, Walker JL, Wright O.The Association between the Mediterranean Dietary Pattern and Cognitive Health: A Systematic Review. Nutrients 2017, 9: 674.
21.   Hardman RJ, Kennedy G, Macpherson H, et al. Adherence to a Mediterranean Style Diet and Effects on Cognition in Adults: A Qualitative Evaluation and Systematic Review of Longitudinal and Prospective Trials. Front Nutr 2016, 3: 22.
22.   Loughrey DG, Lavecchia S, Brennan S, et al. The Impact of the Mediterranean Dieton the Cognitive Functioning of Healthy Older Adults: A Systematic Review and Meta-Analysis. Adv Nutr 2017, 8: 571-586.
23.   Lourida I, Soni M, Thompson-Coon J, et al. Mediterranean diet, cognitive function, and dementia: a systematic review. Epidemiology 2013, 24: 479-489.
doi: 10.1097/EDE.0b013e3182944410 pmid: 23680940
24.   Masana MF, Koyanagi A, Haro JM, et al. n-3 Fatty acids, Mediterranean diet and cognitive function in normal aging: A systematic review. Exp Gerontol 2017, 91: 39-50.
25.   Petersson SD, Philippou E. Mediterranean Diet, Cognitive Function,Dementia: A Systematic Review of the Evidence. Adv Nutr 2016, 7: 889-904.
26.   Psaltopoulou T, Sergentanis TN, Panagiotakos DB, et al. Mediterranean diet, stroke, cognitive impairment, and depression: A meta-analysis. Ann Neurol 2013, 74: 580-591.
doi: 10.1002/ana.23944 pmid: 23720230
27.   Radd-Vagenas S, Duffy SL, Naismith SL, et al. Effect of the Mediterranean diet on cognition and brain morphology and function: a systematic review of randomized controlled trials. Am J Clin Nutr 2018, 107: 389-404.
28.   Singh B, Parsaik AK, Mielke MM, et al. Association of mediterranean diet with mildcognitive impairment and Alzheimer's disease: a systematic review and me-ta-analysis. J Alzheimers Dis 2014, 39: 271-282.
29.   Wu L, Sun D.Adherence to Mediterranean diet and risk of developing cognitive disorders: An updated systematic review and meta-analysis of prospective cohort studies. Sci Rep 20177: 41317.
30.   Keys A, Menotti A, Aravanis C, et al. The seven countries study: 2,289 deaths in 15 years. Prev Med 1984, 13: 141-154.
doi: 10.1016/0091-7435(84)90047-1 pmid: 6739443
31.   Stampfer MJ.Cardiovascular disease and Alzheimer’s disease: common links. J Intern Med 2006, 260: 211-223.
doi: 10.1111/j.1365-2796.2006.01687.x pmid: 16918818
32.   Estruch R, Ros E, Salas-Salvadó J, et al. Primary prevention of cardiovascular dis-ease with a Mediterranean diet. N Engl J Med 2013, 368: 1279-1290.
33.   Scarmeas N, Luchsinger J, Mayeux R.Mediterranean diet and Alzheimer disease mortality. Neurology 2007, 69: 1084-1093.
doi: 10.1212/01.wnl.0000277320.50685.7c pmid: 2673956
34.   Panagiotakos DB, Pitsavos C, Stefanadis C.Dietary patterns: a Mediterranean diet score and its relation to clinical and biological markers of cardiovascular disease risk. Nutr Metab Cardiovasc Dis 2006, 16: 559-568
35.   Gemma C, Vila J, Bachstetter A, et al.Chapter 15 oxidative stress and the aging brain: from theory to prevention. Prevention. In: Riddle DR, editor. Brain Aging: Models, methods, and mechanisms. Boca Raton (FL): CRC Press/Taylor & Francis, 2007: 1-19.
36.   Petersen RC, Thomas RG, Grundman M, et al. Vitamin E and donepezil for the treatment of mild cognitive impairment. N Engl J Med 2005, 352: 2379-2388.
37.   Araújo JR, Martel F, Borges N, et al. Folates and ageing: role in mild cognitive impairment, dementia and depression. Ageing Res Rev 2015, 22: 9-19.
doi: 10.1016/j.arr.2015.04.005 pmid: 25939915
38.   Masaki KH, Losonczy KG, Izmirlian G, et al. Association of vitamin E and C supplement use with cognitive function and dementia in elderly men. Neurology 2000, 54: 1265-1272.
39.   Blazer DG, Yaffe K, Karlawish J.Cognitive aging: A report from the institute of medicine. JAMA 2015, 313: 2121-2122.
doi: 10.1001/jama.2015.4380 pmid: 25875498
40.   Scarmeas N, Stern Y, Tang MX, et al. Mediterranean diet and risk for Alzheimer’s disease. Ann Neurol 2006, 59: 912-921.
doi: 10.1002/ana.20854 pmid: 16622828
41.   Gu Y, Luchsinger JA, Stern Y, et al. Mediterranean diet, inflammatory and metabolic biomarkers, and risk of Alzheimer’s disease. J Alzheimers Dis 2010, 22: 483-492.
doi: 10.3233/JAD-2010-100897 pmid: 3022949
42.   Samieri C, Sun Q, Townsend MK, et al. The association between dietary patterns at midlife and health in aging: an observational study. Ann Intern Med 2013, 159: 584-591.
43.   Samieri C, Okereke OIE, Devore E, et al. Long-term adherence to the Mediterranean diet is associated with overall cognitive status, but not cognitive decline, in women. J Nutr 2013, 143: 493-499.
44.   Koyama A, Houston DK, Simonsick EM, et al. Association between the Mediterranean diet and cognitive decline in a biracial population. J Gerontol A Biol Sci Med Sci 2015, 70: 354-359.
doi: 10.1093/gerona/glu097 pmid: 24994847
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