Table 4 Results of the stratified negative binomial regression analyses for the risk of losing teeth (n = 1694). Adjusted^a relative risks (RR) with 95 % confidence intervals (CI)

Smoking

 0–10 pack-years

1.90 (1.12–3.21)

1.07 (0.68–1.70)

1.34 (0.84–2.14)

1.42 (0.85–2.37)

1.58 (0.85–2.95)

1.35 (0.89–2.04)

 11–20 pack-years

2.27 (1.41–3.65)

1.20 (0.83–1.74)

1.65 (1.16–2.35)

1.35 (0.79–2.30)

1.97 (1.21–3.23)

1.31 (0.90–1.91)

 21 or more pack-years

2.23 (1.52–3.26)

1.41 (0.96–2.08)

1.64 (1.20–2.25)

2.25 (1.35–3.74)

1.81 (1.21–2.70)

1.81 (1.25–2.63)

 Former smoker

1.36 (1.06–1.75)

0.98 (0.78–1.24)

1.14 (0.90–1.44)

1.12 (0.88–1.43)

1.22 (0.92–1.61)

1.09 (0.88–1.34)

 Occasional smoker

1.24 (0.86–1.80)

0.76 (0.52–1.12)

0.99 (0.67–1.45)

1.01 (0.70–1.46)

0.95 (0.62–1.44)

1.01 (0.71–1.42)

 Never smoker (reference)

1.00

1.00

1.00

1.00

1.00

1.00

 1–20 years of smoking

2.00 (1.17–3.42)

1.07 (0.69–1.65)

1.47 (0.96–2.24)

1.28 (0.73–2.25)

1.60 (0.89–2.88)

1.32 (0.87–2.00)

 21–30 years of smoking

2.15 (1.49–3.11)

1.32 (0.95–1.84)

1.68 (1.25–2.26)

1.56 (1.00–2.44)

1.85 (1.25–2.72)

1.55 (1.12–2.14)

 31 or more years of smoking

2.33 (1.40–3.87)

1.26 (0.76–2.08)

1.47 (0.95–2.29)

2.35 (1.31–4.22)

1.95 (1.13–3.36)

1.59 (0.98–2.56)

 Never smoker (reference)

1.00

1.00

1.00

1.00

1.00

1.00