Table 2—

Relative risk of type 2 diabetes according to coffee and tea consumption and caffeine intake

Categories of intake
P value for trend
No cups per dayLess than one cup per dayOne cup per dayTwo to three cups per dayFour or more cups per day
Total coffee
    Median (cups/day)00.431.22.54.6
    n (cases)47928019922778
    Person-years235,047155,431140,041253,35182,248
    Age-adjusted RR10.82 (0.71–0.95)0.59 (0.50–0.70)0.36 (0.31–0.43)0.39 (0.30–0.49)<0.0001
    Multivariate RR*10.93 (0.80–1.09)0.87 (0.73–1.03)0.58 (0.49–0.68)0.53 (0.41–0.68)<0.0001
Caffeinated coffee
    Median (cups/day)00.401.02.54.5
    n (cases)54928518418560
    Person-years291,336166,146139,048208,94560,643
    Age-adjusted RR10.81 (0.71–0.94)0.60 (0.51–0.71)0.41 (0.34–0.48)0.48 (0.36–0.62)<0.0001
    Multivariate RR11.00 (0.86–1.17)0.89 (0.75–1.07)0.62 (0.52–0.74)0.61 (0.46–0.81)<0.0001
Decaffeinated coffee
    Median (cups/day)00.141.02.5
    n (cases)8413137732
    Person-years503,799253,86665,12243,332
    Age-adjusted RR10.62 (0.55–0.71)0.58 (0.46–0.73)0.39 (0.27–0.55)0.0001
    Multivariate RR10.86 (0.74–0.99)0.87 (0.68–1.11)0.52 (0.36–0.74)0.005
Tea
    Median (cups/day)00.211.02.54.5
    n (cases)27158622214242
    Person-years213,433415,827123,77289,87823,209
    Age-adjusted RR10.90 (0.78–1.05)1.18 (0.99–1.41)1.07 (0.87–1.31)1.32 (0.95–1.83)0.005
    Multivariate RR10.97 (0.83–1.12)1.17 (0.97–1.40)0.98 (0.79–1.20)0.88 (0.64–1.23)0.81
CaffeineQuintile 1Quintile 2Quintile 3Quintile 4Quintile 5
    Median (mg/day)2293180341528
    n (cases)281308291218165
    Person-years173,758173,430172,858172,867173,206
    Age-adjusted RR11.05 (0.89–1.23)0.97 (0.82–1.14)0.67 (0.56–0.80)0.51 (0.42–0.62)<0.0001
    Multivariate RR10.88 (0.75–1.04)0.89 (0.75–1.05)0.74 (0.62–0.89)0.55 (0.45–0.67)<0.0001
  • Data are RR (95% CI), unless otherwise indicated.

  • *

    * Adjusted for age (5-year categories), smoking status (never, past, and current), BMI (13 categories), physical activity (quintiles of metabolic equivalent hours per week), alcohol consumption (0, 0.1–4.9, 5.0–9.9, or ≥10 g/day), use of hormone replacement therapy (ever or never), oral contraceptive use (never, past, or current), family history of type 2 diabetes (yes/no), history of hypertension (yes/no), history of hypercholesterolemia (yes/no), consumption of sugar-sweetened soft drinks (4 categories), consumption of punch (4 categories), and quintiles of processed meat consumption, the polyunsaturated-to-saturated fat intake ratio, total energy intake, the glycemic index, and cereal fiber intake. Caffeinated coffee consumption and decaffeinated coffee consumption were simultaneously included in the multivariate model, and the multivariate model for tea included coffee consumption.