Table 1.
Protective factors that are common in non-communicable neurological disorders (i.e., found in more than one disease under consideration)
| 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] |
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
*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
Note: In this table, only statistically significant risk factors that appeared in more than two studies are included