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Table 1 Protective factors that are common in non-communicable neurological disorders (i.e., found in more than one disease under consideration)

From: Non-genetic risk and protective factors and biomarkers for neurological disorders: a meta-umbrella systematic review of umbrella reviews

Factor Effect size metric Effect size (95% CI) Neurological condition (systematic review/meta-analysis) Level of evidence Umbrella review study
Mediterranean diet RR 0.83 (0.75–0.93) Mild cognitive impairment incidence (Wu, 2017) @ IV Galbete, 2018 [84]; Dinu, 2018# [81]
RR 0.60 (0.48–0.77) Alzheimer disease (Wu, 2017) @ IV Galbete, 2018 [84]; Dinu, 2018# [81]
RR 0.69 (0.57–0.84) Mild cognitive impairment incidence/Dementia (Cao, 2016) @ IV Galbete, 2018 [84]
HR 0.73 (0.56–0.96) Mild cognitive impairment incidence (Singh, 2014) @ IV Galbete, 2018 [84]
RR 0.64 (0.46–0.89) Alzheimer disease incidence (Singh, 2014) @ IV Galbete, 2018 [84]
RR 0.84 (0.74–0.95) Stroke (Psaltopoulou, 2013; Cohort studies) @ IV Galbete, 2018 [84]
Dinu, 2018# [81]
RR 0.20 (0.10–0.41) Stroke (Psaltopoulou, 2013; Case-control studies) @ Weak Dinu, 2018 [81]
RR 0.83 (0.66–1.06) Stroke (Psaltopoulou, 2013; Cross-sectional studies) @ No evidence Dinu, 2018 [81]
RR 0.76 (0.60–0.96) Stroke (Grosso, 2014; Cohort studies) @ Weak Dinu, 2018 [81]
RR 0.87 (0.81–0.94) Neurodegenerative diseases (Sofi, 2014) @ Convincing Dinu, 2018 [81]
RR 0.79 (0.70–0.90) Neurodegenerative diseases (Wu, 2017) @ Highly suggestive Dinu, 2018 [81]
RR 0.72 (0.58–0.88) Cognitive impairment (Psaltopoulou, 2013; Cohort studies) @ Suggestive Dinu, 2018 [81]
HR 0.67 (0.55–0.81) Cognitive impairment (Singh, 2014; High-vs.-low MeDi score) @ Suggestive Dinu, 2018 [81]
HR 0.92 (0.88–0.97) Cognitive impairment (Singh, 2014; 1-point increase in MeDi score) @ Suggestive Dinu, 2018 [81]
RR 0.31 (0.16–0.59) Cognitive impairment (Psaltopoulou, 2014; Case-control) @ Weak Dinu, 2018 [81]
RR 0.83 (0.75–0.93) Cognitive impairment (Wu, 2017) @ Highly suggestive Dinu, 2018 [81]
RR 0.69 (0.57–0.84) Dementia Convincing Dinu, 2018 [81]
RR 0.64 (0.47–0.86) Stroke (Grosso, 2014; Randomized trials) @ Weak Dinu, 2018 [81]
Caffeine RR 0.67 (0.57–0.80) Parkinson disease Probable Grosso, 2017 [76]
N/SP 0.78 (0.50–1.22) Alzheimer disease Limited Grosso, 2017 [76]
N/SP 0.79 (0.61–1.04) Cognitive impairment Limited Grosso, 2017 [76]
N/SP 0.82 (0.67–1.01) Cognitive disorders Possible Grosso, 2017 [76]
Coffee consumption RR 0.97 (0.85–1.11) Cognitive decline 6* Poole, 2017 [79]
RR 0.96 (0.83–1.11) Stroke 8* Poole, 2017 [79]
RR 0.98 (0.79–1.23) Glioma 5* Poole, 2017 [79]
RR 0.64 (0.53–0.76) Parkinson disease (Qi, 2014) @ 5* Poole, 2017 [79]
RR 0.64 (0.53–0.77) Parkinson disease (Noyce, 2012) @ 7* Poole, 2017 [79]
RR 0.73 (0.54–0.99) Alzheimer disease (Barranco Quintana, 2017) @ 3* Poole, 2017 [79]
RR 0.70 (0.56–0.88) Parkinson disease (Hernan, 2002) @ Probable Grosso, 2017 [76]
RR 0.73 (0.55–0.97) Alzheimer disease (Liu, 2016) @ Possible Grosso, 2017 [76]
RR 0.67 (0.58–0.76) Parkinson disease (Noyce, 2012)@ III Bellou, 2016 [50]
Alcohol intake RR 0.74 (0.61–0.91) Dementia Weak Bellou, 2017 [49]
RR 0.75 (0.57–0.98) Vascular dementia Weak Bellou, 2017 [49]
RR 0.72 (0.61–0.86) Alzheimer disease Weak Bellou, 2017 [49]
RR 0.75 (0.66–0.85) Parkinson disease III Bellou, 2016 [50]
Physical activity RR 0.76 (0.66–0.86) Dementia Suggestive Bellou, 2017 [49]
RR 0.62 (0.42–0.92) Vascular dementia Weak Bellou, 2017 [49]
HR 0.66 (0.57–0.78) Parkinson disease I Bellou, 2016 [50]
HR 0.62 (0.52–0.72) Alzheimer disease Highly suggestive Bellou, 2017 [49]
Bone mineral density in femoral neck OR 0.36 (0.21–0.61) Multiple sclerosis Weak Belbasis, 2015 [18, 51]
OR 0.25 (0.09–0.66) Parkinson disease IV Bellou, 2016 [50]
Bone mineral density in hip OR 0.33 (0.18–0.60) Multiple sclerosis Weak Belbasis, 2015 [18, 51]
OR 0.55 (0.38–0.80) Parkinson disease IV Bellou, 2016 [50]
Bone mineral density in lumbar spine OR 0.34 (0.24–0.50) Multiple sclerosis Weak Belbasis, 2015 [18, 51]
OR 0.29 (0.16–0.54) Parkinson disease IV Bellou, 2016 [50]
Serum vitamin D SMD to RR 0.08 (0.01–0.63) Alzheimer disease No conclusion Theodoratou, 2014 [52]
OR 0.42 (0.34–0.53) Cognition Suggestive Theodoratou, 2014 [52]
RR 0.61 (0.50–0.75) Stroke Suggestive Theodoratou, 2014 [52]
HR 0.66 (0.55–0.80) Ischemic stroke Suggestive Theodoratou, 2014 [52]
OR 0.52 (0.44–0.61) Ischemic stroke Suggestive Theodoratou, 2014 [52]
OR 0.16 (0.05–0.50) Parkinson disease IV Bellou, 2016 [50]
OR 0.44 (0.24–0.70) Multiple sclerosis Weak Belbasis, 2015 [18, 51]
Serum vitamin B12 OR 0.64 (0.44–0.93) Multiple sclerosis Suggestive Belbasis, 2015 [18, 51]
OR 0.50 (0.40–0.63) Parkinson disease IV Bellou, 2016 [50]
Vitamin E dietary intake RR 0.80 (0.67–0.95) Alzheimer disease Weak Bellou, 2017 [49]
OR 0.81 (0.67–0.98) Parkinson disease IV Bellou, 2016 [50]
Statins RR 0.83 (0.76–0.91) Dementia Suggestive Bellou, 2017 [49]
RR 0.72 (0.59–0.89) Alzheimer disease Weak Bellou, 2017 [49]
RR 0.77 (0.64–0.92) Parkinson disease IV Bellou, 2016 [50]
Antihypertensive drugs HR 0.84 (0.75–0.94) Dementia Weak Bellou, 2017 [49]
RR 0.64 (0.42–0.98) Vascular dementia Weak Bellou, 2017 [49]
Non-aspirin NSAIDS RR 0.85 (0.77–0.94) Parkinson disease IV Bellou, 2016 [50]
RR 0.65 (0.49–0.86) Alzheimer disease Weak Bellou, 2017 [49]
  1. Abbreviations: N/A not available, OR odds ratio, RR relative risk, HR hazard ratio, SMD standardized mean difference, N/SP not specified (either OR or RR), 95% CI 95% confidence interval
  2. *According to AMSTAR classification. # Overlapping studies. @These refer to metrics (e.g., RRs, HRs) of the original systematic reviews included in the umbrella reviews. The full citations of these original systematic reviews/meta-analyses are included in the corresponding umbrella reviews
  3. Note: In this table, only statistically significant risk factors that appeared in more than two studies are included