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Table 1 Characteristics of whole sample, and split by type-2 diabetes and non-type-2 diabetes group [continuous variables: mean (± standard deviation); categorical variables: frequency (% of total)]

From: Assessment of CYP1A2 enzyme activity in relation to type-2 diabetes and habitual caffeine intake

Variable Whole sample (n = 203) Type-2 diabetes cases (n = 57) Non-type-2 diabetes controls (n = 146) p-value between groups
Age (years) 59.3 (±15.9) 63.9 (±9.9) 57.4 (±17.4) 0.008
Male Gender (%) 87 (42.9 %) 38 (66.7 %) 49 (33.6 %) <0.001
Body Mass Index (BMI; kg/m2)a 25.1 (±4.5) 28.6 (±5.3) 23.7 (±3.3) <0.001
Overweight/Obese BMI (%)b 84 (41.8 %) 42 (73.7 %) 42 (29.2 %) <0.001
Smoking (% yes) 21 (10.3 %) 9 (15.8 %) 12 (8.2 %) 0.127
Alcohol Intake (% yes)c 78 (38.4 %) 16 (28.1 %) 62 (42.5 %) 0.077
Long-Term Medication (% yes) 129 (63.5 %) 55 (96.5 %) 74 (50.7 %) <0.001
Oral Medication for Diabetes (% yes) 42 (20.7 %) 42 (73.7 %) 0 (0 %) <0.001
Insulin Injections for Diabetes (% yes) 19 (9.4 %) 19 (33.3 %) 0 (0 %) <0.001
Contraceptive Pill (% yes) 9 (4.4 %) 0 (0 %) 9 (6.2 %) 0.064
Total Habitual Caffeine Intake (mg/day)d 295.8 (±158.1) 365.2 (±191.3) 268.7 (±134.4) <0.001
Caffeine from Coffee (mg/day)d, e 240.3 (±162.2) 306.9 (±195.7) 214.3 (±139.4) 0.001
Higher Habitual Caffeine Intake (% yes)f 64 (31.5 %) 28 (49.1 %) 36 (24.7 %) 0.001
Salivary Caffeine Concentration (μmol/l)d 11.0 (±7.7) 11.9 (±8.2) 10.6 (±7.6) 0.259
Salivary Paraxanthine Concentration (μmol/l)d 5.2 (±3.4) 6.0 (±3.4) 4.9 (±3.4) 0.024
Time between saliva sample and final caffeine portion (h) 6.7 (±2.6) 5.8 (±2.6) 7.1 (±2.5) 0.001
Gene Cytochrome P450-1A2 (CYP1A2)g
Allele Frequency (%) A 276 (69.0 %) 83 (74.1 %) 193 (67.0 %) 0.186
C 124 (31.0 %) 29 (25.9 %) 95 (33.0 %)
Genotype Frequency (%)      0.036
  A/A 97 (48.5 %) 34 (60.7 %) 63 (43.8 %) 0.040
C/A 82 (41.0 %) 15 (26.8 %) 67 (46.5 %) 0.011
C/C 21 (10.5 %) 7 (12.5 %) 14 (9.7 %) 0.610
Enzyme Inducibility (%) High 97 (48.5 %) 34 (60.7 %) 63 (43.8 %) 0.040
Less 103 (51.5 %) 22 (39.3 %) 81 (56.3 %)
  1. Abbreviations T2D type-2 diabetes, Non-T2D non-type-2 diabetes, Data for continuous variables are means (± standard deviation) of raw data. P-values (2-tailed) were calculated using independent samples t-tests, comparing T2D and Non-T2D groups, on raw data. If raw data was abnormally distributed, the data was transformed to achieve a normal distribution before the t-test was applied (method of transformation noted in legend). Data for categorical variables are frequencies (%). P-values (exact; 2-tailed) were calculated using Fisher’s exact test
  2. aRaw data transformation: Log10; T2D (n = 57); Non-T2D (n = 144). bOverweight/Obese BMI >24.9 vs. Underweight/Healthy BMI ≤24.9; T2D (n = 57); Non-T2D (n = 144). cConsume 3 or more alcoholic drinks per week. dRaw data transformation: Square root. eIncludes caffeine from decaffeinated coffee (4.5 mg/cup). fHigher habitual caffeine intake (> Swiss average of 288 mg/day) vs. Lower/Normal habitual caffeine intake (≤ Swiss average). gSNP ID: rs762551. T2D (n = 56); Non-T2D (n = 144). Highly inducible = genotype A/A. Less inducible = genotypes A/C and C/C