American Diabetes Association

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Table 3—

Risk of type 2 diabetes by combinations of total coffee consumption and caffeine intake

	Quintiles of caffeine intake
	Q1–Q2	Q3	Q4–Q5
Total coffee less than one cup per day
Median coffee consumption (cups/day)	0	0	0
Median caffeine intake (mg/day)	52	173	287
Number of cases/person-years	533/292,658	184/79,183	42/18,638
RR (95% CI)	1 (ref.)	1.02 (0.86–1.21)	0.85 (0.62–1.16)
Total coffee 1.0–1.9 cups/day
Median coffee consumption (cups/day)	1.1	1.1	1.6
Median caffeine intake (mg/day)	74	186	297
Number of cases/person-years	38/31,550	87/68,142	74/40,348
RR (95% CI)	0.89 (0.63–1.23)	0.88 (0.70–1.10)	0.90 (0.70–1.16)
Total coffee two or more cups per day
Median coffee consumption (cups/day)	2.5	2.5	2.6
Median caffeine intake (mg/day)	51	189	430
Number of cases/person-years	18/22,979	20/25,533	267/287,087
RR (95% CI)	0.52 (0.32–0.83)	0.50 (0.32–0.79)	0.59 (0.50–0.69)

	Quintiles of caffeine intake
	Q1–Q2	Q3	Q4–Q5
Total coffee less than one cup per day
Median coffee consumption (cups/day)	0	0	0
Median caffeine intake (mg/day)	52	173	287
Number of cases/person-years	533/292,658	184/79,183	42/18,638
RR (95% CI)	1 (ref.)	1.02 (0.86–1.21)	0.85 (0.62–1.16)
Total coffee 1.0–1.9 cups/day
Median coffee consumption (cups/day)	1.1	1.1	1.6
Median caffeine intake (mg/day)	74	186	297
Number of cases/person-years	38/31,550	87/68,142	74/40,348
RR (95% CI)	0.89 (0.63–1.23)	0.88 (0.70–1.10)	0.90 (0.70–1.16)
Total coffee two or more cups per day
Median coffee consumption (cups/day)	2.5	2.5	2.6
Median caffeine intake (mg/day)	51	189	430
Number of cases/person-years	18/22,979	20/25,533	267/287,087
RR (95% CI)	0.52 (0.32–0.83)	0.50 (0.32–0.79)	0.59 (0.50–0.69)

RRs were multivariate adjusted as described in the legend of Table 2.