TABLE 1.
Characteristics of women participating in the BioCycle Study, by average caffeine intake and anovulatory status1
| Caffeine intake (mg/d) |
Anovulatory2 |
|||||||
| Total | <25 | 25–105 | >105 | P | Yes | No | P | |
| Number of participants [n (%)] | 259 | 86 (33.2) | 84 (32.4) | 89 (34.4) | 35 (13.5) | 224 (86.5) | ||
| Caffeine (mg/d) | 90.9 ± 94.03 | 10.9 ± 8.1 | 58.0 ± 23.7 | 199.4 ± 79.7 | <0.0001 | 60.2 ± 80.0 | 95.7 ± 95.8 | 0.04 |
| Demographic and lifestyle characteristics | ||||||||
| Age (y) | 27.3 ± 8.2 | 23.4 ± 5.8 | 26.5 ± 8.0 | 31.7 ± 8.3 | <0.0001 | 22.5 ± 5.6 | 28.0 ± 8.3 | 0.0002 |
| Race [n (%)] | <0.0001 | 0.27 | ||||||
| White | 154 (59.5) | 37 (43.0) | 49 (58.3) | 68 (76.4) | 20 (57.1) | 134(59.8) | ||
| Black | 51 (19.7) | 31 (36.1) | 14 (16.7) | 6 (6.7) | 8 (22.9) | 43 (19.2) | ||
| Asian | 37 (14.3) | 15 (17.4) | 13 (15.5) | 9 (10.1) | 7 (20.0) | 30 (13.4) | ||
| Other | 17 (6.6) | 3 (3.5) | 8 (9.5) | 6 (6.7) | 0 (0.0) | 17 (7.6) | ||
| BMI (kg/m2) | 24.1 ± 3.9 | 23.4 ± 3.6 | 24.6 ± 4.1 | 24.2 ± 3.8 | 0.11 | 23.4 ± 3.8 | 24.2 ± 3.9 | 0.25 |
| Waist-to-hip ratio | 0.75 ± 0.06 | 0.75 ± 0.06 | 0.75 ± 0.05 | 0.75 ± 0.05 | 0.90 | 0.75 ± 0.05 | 0.75 ± 0.06 | 0.51 |
| Nulligravid [n (%)] | 177 (69.4) | 71 (83.5) | 62 (74.7) | 44 (50.6) | <0.0001 | 28 (84.9) | 149 (67.1) | 0.04 |
| Perceived stress score | 20.2 ± 6.8 | 21.7 ± 74 | 20.3 ± 6.1 | 18.6 ± 6.5 | 0.01 | 20.2 ± 6.9 | 20.2 ± 6.8 | 0.99 |
| Cigarette use [n (%)] | 0.02 | 0.79 | ||||||
| No | 218 (84.2) | 80 (93.0) | 67 (79.8) | 71 (79.8) | 30 (85.7) | 188 (83.9) | ||
| Yes | 41 (15.8) | 6 (7.0) | 17 (20.2) | 18 (20.2) | 5 (14.3) | 36 (16.1) | ||
| Sleep (h) | 7.2 ± 0.8 | 7.1 ± 0.9 | 7.2 ± 0.7 | 7.2 ± 0.7 | 0.80 | 6.8 ± 0.7 | 7.2 ± 0.8 | 0.01 |
| Daily exercise (min/d) | 14.7 ± 21.9 | 10.9 ± 12.7 | 16.7 ± 27.0 | 16.5 ± 23.4 | 0.14 | 20.4 ± 25.2 | 13.9 ± 21.3 | 0.10 |
| Sex (intercourse/d) | 0.09 ± 0.13 | 0.07 ± 0.12 | 0.08 ± 0.12 | 0.11 ± 0.14 | 0.10 | 0.05 ± 0.11 | 0.09 ± 0.13 | 0.09 |
| Diet | ||||||||
| Total energy (kcal) | 1613.3 ± 367.3 | 1519.6 ± 342.2 | 1600.0 ± 351.5 | 1716.5 ± 382.6 | 0.002 | 1621.2 ± 424.7 | 1612.1 ± 358.6 | 0.89 |
| Alcohol (g) | 2.8 ± 5.5 | 1.0 ± 1.9 | 2.3 ± 4.7 | 4.9 ± 7.4 | <0.0001 | 1.0 ± 2.1 | 3.0 ± 5.8 | 0.0001 |
| Carbohydrates (% of energy) | 50.8 ± 7.3 | 51.7 ± 7.5 | 51.3 ± 7.3 | 49.4 ± 6.9 | 0.09 | 49.9 ± 8.4 | 50.9 ± 7.1 | 0.46 |
| Protein (% of energy) | 15.8 ± 3.1 | 16.0 ± 3.7 | 15.8 ± 3.0 | 15.7 ± 2.6 | 0.86 | 16.3 ± 3.8 | 15.7 ± 3.0 | 0.30 |
| Fat (% of energy) | 33.8 ± 5.6 | 33.3 ± 5.5 | 33.5 ± 5.7 | 34.6 ± 5.5 | 0.25 | 35.2 ± 5.9 | 33.6 ± 5.5 | 0.12 |
| Cholesterol (mg/d) | 213.3 ± 106.7 | 196.8 ± 112.0 | 220.9 ± 111.6 | 222.1 ± 95.4 | 0.21 | 231.3 ± 128.1 | 210.5 ± 103.3 | 0.28 |
| Fiber (g/d) | 13.6 ± 5.6 | 12.7 ± 5.5 | 13.2 ± 6.1 | 15.0 ± 4.8 | 0.02 | 15.7 ± 8.2 | 13.3 ± 5.0 | 0.11 |
| Total E2 (pg/mL) | 104.3 (83.3–134.4)4 | 111.1 (83.3–144.8) | 102.7 (83.9–131.6) | 101.6 (84.5–128.8) | 0.57 | 60.3 ± 1.4 | 90.0 ± 1.4 | <0.0001 |
| Free E2 (pg/mL) | 1.3 (1.1–1.6) | 1.3 (1.1–1.7) | 1.3 (1.1–1.5) | 1.3 (1.0–1.5) | 0.24 | 1.0 ± 0.3 | 1.4 ± 0.5 | <0.0001 |
| Luteal progesterone (ng/mL) | 3.4 (2.5–4.4) | 3.3 (2.5–4.5) | 3.0 (2.3–4.2) | 3.7 (2.8–4.4) | 0.19 | 0.69 ± 1.7 | 1.5 ± 1.5 | <0.0001 |
| LH (ng/mL) | 9.2 (7.5–11.4) | 9.2 (7.7–11.4) | 9.1 (7.5–11.4) | 9.2 (7.5–11.3) | 0.59 | 6.7 ± 15 | 6.0 ± 1.4 | 0.27 |
| FSH (mIU/mL) | 6.0 (5.1–7.0) | 5.7 (4.6–6.6) | 6.5 (5.2–7.1) | 7.0 (5.4–7.5) | 0.0004 | 5.3 ± 1.3 | 5.4 ± 1.3 | 0.78 |
| Other biomarkers | ||||||||
| Cholesterol (mg/dL) | 163.2 (147.4–177.9) | 159.8 (145.3–176.9) | 158.9 (146.1–176.4) | 169.1 (153.6–186.3) | 0.04 | 161.8 ± 25.3 | 164.8 ± 27.4 | 0.54 |
| Insulin resistance (mmol/L) | 1.5 (1.1–2.1) | 1.7 (1.2–2.6) | 1.5 (1.2–2.1) | 1.3 (1.0–1.9) | 0.02 | 2.0 ± 1.1 | 1.8 ± 1.3 | 0.42 |
1
ANOVA for continuous variables and exact chi-square tests for categorical variables were used to test associations between caffeine intake or ovulation status. Reproductive hormones and serum cholesterol were log transformed for normality for statistical analyses. E2, estradiol; FSH; follicle-stimulating hormone; LH, luteinizing hormone.
2
Defined as having at least one anovulatory cycle over the 2-cycle study period; 28 women had 1 anovulatory cycle, and 7 women had 2 anovulatory cycles.
3
Mean ± SD (all such values).
4
Median; interquartile range in parentheses (all such values).