Table 1.
Overview of studies evaluating the association between oral health and cognition
| Study | Study type | Population | Outcome(s) | Results |
|---|---|---|---|---|
| Luo et al., 2015 | Human cohort study |
Dementia (n = 120) MCI (n = 554) Cognitive normal (n = 2,389) |
Mean (SD) teeth missing |
Dementia: 18.7 (11.0) MCI: 11.8 (9.9) Cognitive normal: 9.3 (9.3) |
| Park et al., 2013 | Human cohort study |
Number of teeth lost: 6–10 teeth >10 teeth |
Cognitive impairment based on MMSE < 24 |
6–10 teeth: aOR 1.99, 95% CI 1.08–3.69 >10 teeth: aOR 2.25, 95% CI 1.26–4.02 |
| Takeuchi et al., 2017 | Human cohort study |
Number of remaining teeth: ≥20 (n = 893) 10–19 (n = 328) 1–9 (n = 204) 0 (n = 121) |
All‐cause dementia |
10–19: aHR 1.62, 95% CI 1.06–2.46 1–9: aHR 1.81, 95% CI 2.94 0: aHR 1.63, 95% 0.95–2.80 |
| Gatz et al., 2006 | Human case–control twin study |
Demented (n = 82) Not demented (n = 82) |
Oral disease from tooth loss | Demented versus non‐demented: OR 3.6, 95% CI 1.34–9.70 |
| Stein et al., 2007 | Human cohort study |
Number of non‐third molars: 0 (n = 25) 1–9 (n = 26) 10–16 (n = 27) 17–28 (n = 66) Number of non‐third molars with apoE4 allele: 0 (n = 3) 1–9 (n = 6) 10–16 (n = 5) 17–28 (n = 18) |
Dementia |
All participants 0: OR 0.9, 95% CI 0.25–3.12 1–9: OR 1.8, 95% CI 0.58–5.46 10–16: OR 0.4, 95% 0.10–1.76 ApoE4 allele: 0: OR 0.1, 95% CI 0.01–3.7 1–9: OR 0.5, 95% CI 0.04–5.6 10–16: OR 0.3, 95% CI 0.02–3.6 |
| Shimazaki et al., 2001 | Human cohort study |
Dentition status: >20 teeth (n = 150) 1–19 teeth with dentures (n = 440) 1–19 teeth not using dentures (n = 371) Edentulous using dentures (n = 621) Edentulous not using dentures (n = 347) |
Six‐year mental impairment |
1–19 teeth with dentures: OR 1.9, 95% CI 0.8–4.6 1–19 teeth not using dentures: OR 2.3, 95% CI 0.9–5.8 Edentulous using dentures: OR 1.7, 95% CI 0.7–4.0 Edentulous not using dentures: OR 2.4, 95% CI 0.9–6.5 |
| Stewart et al., 2013 | Human cohort study |
Quartile of oral health parameters: Q1 (n = 264) Q2 (n = 186) Q3 (n = 110) Q4 (n = 46) |
Cognitive impairment |
Per oral health quartile increase: OR 0.56, 95% CI 0.48–0.67 |
| Chen et al., 2015 | Human cross‐sectional study |
CIND (n = 57) Dementia (n = 51) No cognitive impairment (n = 492) |
Number of carious teeth or retained roots while adjusting for the capacity to perform oral hygiene |
CIND: RR 1.66, 95% CI 1.13–2.46 Dementia: RR 1.82, 95% CI 1.23–2.70 |
| Cho et al., 2018 | Human cohort study |
Normal cognitive ability (n = 284) Dementia (n = 61) |
Oral health | Demented versus non‐demented: OR 2.29, 95% CI 1.08–4.83 |
| Oue et al., 2013 | Interventional, prospective study (J20 mice) |
Maxillary molar teeth removed (n = 10) Control group with intact molars (n = 10) |
Impact of tooth loss on acquisition (learning) versus retention (memory) latency |
Retention versus acquisition latency (p < .05) Retention latency: 293.6 + 6.1 s Acquisition latency: 88.9 + 17.4 s |
| Oue et al., 2016 | Interventional, prospective study (Tg2576 mice) |
Maxillary molar teeth removed (n = 9) Control group with intact molars (n = 10) |
Impact of tooth loss on acquisition (learning) and retention (memory) latency |
Acquisition latency (p > .05): Molar teeth removed: 89.0 + 17.9 s Control group: 172.0 + 40.7 s Retention latency (p < .05): Molar teeth removed: 300.0 + 0 s Control group: 296.7 + 3.3 s |
| He et al., 2014 | Interventional, prospective study (SAMP8 mice) |
4‐month‐old mice: Alveolar nerve transection (experimental) (n = 20) Sham surgery (control) (n = 20) 7‐month‐old mice: Alveolar nerve transection (experimental) (n = 10) Sham surgery (control) (n = 10) |
Escape latency Learning rate |
Escape latency significantly greater in elderly experimental group than elderly control group in five‐minute acquisition session (p < .05) Elderly control: 39.70 + 14.84 s Elderly experimental: 63.60 + 15.31 s Learning rate in elderly mice significantly poorer in experimental group versus controls (p < .05) Elderly control: 18.50 + 5.44 Elderly experimental: 25.90 + 6.21 |
| Kubo et al., 2017 | Interventional, prospective study (SAMP8 mice) |
Molars removed (n = 33) Molars intact (n = 33) |
Plasma cortisol levels Time in Morris water maze |
Higher plasma cortisone levels in early tooth loss group (p = .016) Early tooth loss group required more time in Morris water maze test (p = .016) |
Abbreviations: aHR, adjusted hazard ratio; aOR, adjusted odds ratio; CIND, cognitive impairment, no dementia; MCI, mild cognitive impairment; MMSE, mini‐mental state examination; RR, relative risk; SD, standard deviation.