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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) 0.43 1.2 2.5 4.6  
    n (cases) 479 280 199 227 78  
    Person-years 235,047 155,431 140,041 253,351 82,248  
    Age-adjusted RR 0.82 (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* 0.93 (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) 0.40 1.0 2.5 4.5  
    n (cases) 549 285 184 185 60  
    Person-years 291,336 166,146 139,048 208,945 60,643  
    Age-adjusted RR 0.81 (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 RR 1.00 (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) 0.14 1.0 2.5   
    n (cases) 841 313 77 32   
    Person-years 503,799 253,866 65,122 43,332   
    Age-adjusted RR 0.62 (0.55–0.71) 0.58 (0.46–0.73) 0.39 (0.27–0.55)  0.0001 
    Multivariate RR 0.86 (0.74–0.99) 0.87 (0.68–1.11) 0.52 (0.36–0.74)  0.005 
Tea    
 
  
    Median (cups/day) 0.21 1.0 2.5 4.5  
    n (cases) 271 586 222 142 42  
    Person-years 213,433 415,827 123,772 89,878 23,209  
    Age-adjusted RR 0.90 (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 RR 0.97 (0.83–1.12) 1.17 (0.97–1.40) 0.98 (0.79–1.20) 0.88 (0.64–1.23) 0.81 
Caffeine Quintile 1 Quintile 2 Quintile 3 Quintile 4 Quintile 5  
    Median (mg/day) 22 93 180 341 528  
    n (cases) 281 308 291 218 165  
    Person-years 173,758 173,430 172,858 172,867 173,206  
    Age-adjusted RR 1.05 (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 RR 0.88 (0.75–1.04) 0.89 (0.75–1.05) 0.74 (0.62–0.89) 0.55 (0.45–0.67) <0.0001 
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) 0.43 1.2 2.5 4.6  
    n (cases) 479 280 199 227 78  
    Person-years 235,047 155,431 140,041 253,351 82,248  
    Age-adjusted RR 0.82 (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* 0.93 (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) 0.40 1.0 2.5 4.5  
    n (cases) 549 285 184 185 60  
    Person-years 291,336 166,146 139,048 208,945 60,643  
    Age-adjusted RR 0.81 (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 RR 1.00 (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) 0.14 1.0 2.5   
    n (cases) 841 313 77 32   
    Person-years 503,799 253,866 65,122 43,332   
    Age-adjusted RR 0.62 (0.55–0.71) 0.58 (0.46–0.73) 0.39 (0.27–0.55)  0.0001 
    Multivariate RR 0.86 (0.74–0.99) 0.87 (0.68–1.11) 0.52 (0.36–0.74)  0.005 
Tea    
 
  
    Median (cups/day) 0.21 1.0 2.5 4.5  
    n (cases) 271 586 222 142 42  
    Person-years 213,433 415,827 123,772 89,878 23,209  
    Age-adjusted RR 0.90 (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 RR 0.97 (0.83–1.12) 1.17 (0.97–1.40) 0.98 (0.79–1.20) 0.88 (0.64–1.23) 0.81 
Caffeine Quintile 1 Quintile 2 Quintile 3 Quintile 4 Quintile 5  
    Median (mg/day) 22 93 180 341 528  
    n (cases) 281 308 291 218 165  
    Person-years 173,758 173,430 172,858 172,867 173,206  
    Age-adjusted RR 1.05 (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 RR 0.88 (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.

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