Table 2 Summary of cohort studies included in the meta-analysis
Author /Year | Country | Sample size | Study design | Age, yr | Main exposure definition | Exposure cut-off point | Accessment of cognitive function | Effect size and crude association results with 95%CI highest vs. lowest category | Effect size and adjusted association results with 95%CI highest vs. lowest category | Adjustment | Follow- up, yr | Quality scores |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Takeuchi et al (2017) [30] | Japan | 1566 | Cohort | ≥60 | Number of teeth present | ≥20, 10–19, 1–9, 0 | DSM-III R | 3.83 (2.47–5.93) | 1.63 (0.95–2.80) | Sex, age, occupation, education, hypertension, diabetes mellitus, history of stroke, alcohol intake, tooth brushing frequency, regular visits to the dentist, and denture use. | 5 | 16 |
Stewart et al (2015) [31] | Sweden | 697 | Cohort | 70–92 | Number of teeth present | ≥25, 21–24, 9–20, 0–8, | DSM-III R | – | 1.62 (0.84–3.11) | Age, education, social class, and vascular risk factors | 37 | 13 |
Batty et al (2013) [30] | 20 Countries | 11,140 | Cohort | 55–88 | Number of teeth present | ≥22, 1–21, 0 | MMSE | – | 1.48 (1.24–1.78) | Age, sex, socio-economic CVD risk factors, treatment allocation and ethnicity | 5 | 14 |
Yamamoto et al (2012) [32] | Japan | 4425 | Cohort | ≥65 | Number of teeth present | ≥20, ≤19, 0 | Standardized questionnaire | 3.42 (1.05–11.08) | 1.41 (0.42–4.70) | Age, adjusted household income, BMI, present illness, alcohol consumption, exercise, and forgetfulness | 4 | 15 |
Paganini-Hill et al (2012) [33] | USA | 5468 | Cohort | 52–105 | Number of teeth present | 26–32, 16–25, 1–15, 0 | MMSE | 0.84 (0.67–1.06) | – | – | 18 | 13 |
Arrivé et al (2011) [34] | France | 405 | Cohort. | 66–80 | Number of teeth missing | < 11 ≥11 | DSM-III R | 1.35 (0.81–2.25) | – | – | 15 | 12 |
Kim et al. (2007) [35] | Korea | 686 | Cohort | ≥65 | Number of teeth present | ≥28 25–27, 15–24, 1–14, 0 | DSM-IV | 1.38 (1.12–1.69) | 1.26 (1.00–1.59) | Age, gender and education, reported diet, vascular disease/risk, BMI and MAC, albumin and cholesterol | 2.4 | 14 |
Stein et al (2007) [26] | USA | 101 | Cohort | 75–98 | Number of teeth present | 10–28, 0–9 | MMSE | 2.69 (1.07–6.73) | 2.20 (1.10–4.50) | Age, education, and apolipoprotein E4 allele | 12 | 13 |
Shimazakil et al (2001) [36] | Japan | 517 | Cohort study | ≥65 | Number of teeth present | >20, 1–19, 0 | Historical diagnosis information from medical records | 5.20 (2.00–13.10) | 2.40 (0.90–6.50) | Age, and classification of institution, physical health status, and cerebrovascular disorder | 6 | 13 |