Table 1—

Baseline characteristics and adiponectin levels of diabetic and nondiabetic subjects categorized into quartiles of caffeine-containing coffee (cups) or caffeine (milligrams) consumption

VariableCaffeine-containing coffee consumption (cups)
P
<1 per week1–6 per week1–3 per day≥4 per day
Baseline characteristics
    Diabetic subjects
        n269224387102
        Adiponectin (μg/ml)5.7 (3.4–8.6)5.7 (3.6–8.5)5.2 (3.5–8.7)6.6 (4.2–12.1)0.002
        Demographic
            Age (years)58.6 ± 6.759.2 ± 6.759 ± 6.758.1 ± 5.90.44
            BMI (kg/m2)30.4 ± 6.530.8 ± 6.429.5 ± 5.928.5 ± 6.80.005
            Waist-to-hip ratio0.85 ± 0.130.84 ± 0.070.83 ± 0.070.83 ± 0.10.41
            Physical activity (METs/week)12.7 ± 17.612.4 ± 14.811.1 ± 14.410.2 ± 140.39
            Total energy intake (kcal)1713 ± 4961762 ± 4651833 ± 4381842 ± 4950.006
            Alcohol (g/day)2.2 ± 7.32.7 ± 5.84.7 ± 9.04.4 ± 9.10.0002
            Caffeine (mg/day)83 ± 69185 ± 97336 ± 114630 ± 141<0.0001
            Current smoker19 (7)21 (9)58 (15)38 (34)<0.0001
            Married221 (87)175 (81)294 (80)86 (77)0.07
            Bachelor's degree or higher66 (26)54 (25)82 (22)26 (23)0.71
            Full-time employment64 (25)58 (27)103 (28)33 (29)0.82
        Medical history
            Hypertension127 (47)89 (40)157 (41)38 (33)0.06
            Hypercholesterolemia113 (42)95 (42)151 (40)37 (32)0.30
            Family history of diabetes124 (46)104 (46)208 (55)66 (58)0.03
    Nondiabetic Subjects
        n276232444106
        Adiponectin (μg/ml)18.3 (12.6–23.6)17.8 (13.3–22.7)17.4 (12.8–22.5)20.1 (15.1–23.1)0.06
        Demographic
            Age (years)56.6 ± 7.457.1 ± 6.756.2 ± 6.855.0 ± 6.40.06
            BMI (kg/m2)25.7 ± 5.926.6 ± 6.026.4 ± 6.125.8 ± 5.70.32
            Waist-to-hip ratio0.77 ± 0.060.79 ± 0.080.77 ± 0.060.77 ± 0.060.11
            Physical activity (METs/week)13.2 ± 16.115.7 ± 18.412.9 ± 14.419.7 ± 35.20.006
            Total energy intake (kcal)1746 ± 4351739 ± 4341750 ± 4551897 ± 4820.01
            Alcohol (g/day)5.1 ± 9.26.2 ± 9.06.9 ± 9.76.2 ± 9.60.09
            Caffeine (mg/day)90 ± 84200 ± 99354 ± 108645 ± 142<0.0001
            Current smoker17 (6)24 (10)55 (12)26 (25)<0.0001
            Married223 (82)183 (81)375 (86)80 (82)0.30
            Bachelor's degree or higher94 (35)70 (31)140 (32)27 (28)0.63
            Full-time employment88 (33)60 (27)163 (37)43 (44)0.007
        Medical history
            Hypertension31 (11)49 (21)84 (19)19 (18)0.02
            Hypercholesterolemia75 (27)79 (34)127 (29)27 (25)0.26
            Family history of diabetes56 (20)44 (19)101 (23)17 (16)0.40
Adiponectin (μg/ml)
    Diabetic subjects
        n269224387102
        Unadjusted5.7 (1.0–41.8)5.8 (1.2–35.9)5.5 (1.1–30.2)7.3 (1.3–31.7)0.002
        Model 15.45.55.16.50.01
        Model 25.05.24.86.40.002
        Model 36.16.35.97.70.004
    Nondiabetic subjects
        n276232444106
        Unadjusted16.9 (12.6–23.6)16.8 (13.3–22.7)16.5 (23.8–22.5)19.0 (15.1–23.14)0.06
        Model 114.514.714.316.30.06
        Model 214.013.913.615.90.04
        Model 313.213.212.915.00.04
Caffeine Q1Caffeine Q2Caffeine Q3Caffeine Q4P
Diabetic subjects
    n243244245245
    Unadjusted5.6 (3.5–8.0)5.4 (6.4–8.2)5.6 (3.5–8.9)6.4 (3.8–10.8)0.02
    Model 14.64.64.65.60.04
    Model 24.84.84.85.80.003
    Model 36.05.85.97.00.004
Nondiabetic subjects
    n255247284272
    Unadjusted16.9 (12.7–24.2)16.6 (12.9–22.2)16.4 (12.7–22.9)17.6 (13.9–23.4)0.36
    Model 114.614.314.315.30.29
    Model 214.313.613.614.70.17
    Model 313.512.912.913.90.18
  • Data are median (interquartile range), means ± SD, and n (%) for baseline characteristics and modeled median (interquartile range) and geometric mean % for adiponectin data. P values determined by ANOVA for continuous measures with logarithmic transformation of biomarkers and χ2 tests for categorical variables. Model 1: adjusted for age and BMI; model 2: adjusted additionally for physical activity (METs/week), total energy intake, alcohol intake (g/day), and smoking status (never, former, or current); model 3: adjusted additionally for hypertension, hypercholesterolemia, A1C, family history of diabetes, aspirin, postmenopausal hormone use, use of ACE inhibitors and other blood pressure medication, and oral diabetes medication use (A1C, insulin and oral diabetes medication not adjusted for in healthy women). Dichotomous (yes/no) variables and continuous measures categorized into quintiles and modeled using indicator variables. P values for differences between categories determined from multivariate linear regression models. For women with diabetes, data were missing for caffeine intake (n = 5), so the numbers will be less than the total sample size (n = 982). Q1, quartile 1 (0–100 mg); Q2, quartile 2 (101–237 mg); Q3, quartile 3 (237–378 mg); Q4, quartile 4 (379–967 mg).