Table 2. Prevalence ratios (PRs) and 95% confidence intervals for dental caries according to duration of breastfeeding in 2056 children (FCHS, Japan).

	Prevalence	Crude PR (95% CI)	Adjusted PR (95% CI)a
Breastfeeding duration (months)
<6	85/416 (20.4%)	1.00	1.00
6–11	74/498 (14.9%)	0.73 (0.55–0.97)	0.79 (0.60–1.05)
12–17	90/583 (15.4%)	0.76 (0.58–0.99)	0.86 (0.66–1.13)
≥18	176/559 (31.5%)	1.54 (1.23–1.93)	1.66 (1.33–2.06)
P for linear trend		<0.0001	<0.0001
P for quadratic trend		<0.0001	<0.0001

FCHS, Fukuoka Child Health Study.

^aAdjusted for sex, toothbrushing frequency, use of fluoride, regular dental check-ups, between-meal snack frequency, maternal smoking during pregnancy, exposure to environmental tobacco smoke at home, and paternal and maternal educational levels.