Table 2.
Correlates of short and long menstrual cycle length among nulliparous Danish women in the Snart-Gravid study (n = 1,940*)
| Short cycle (≥25 days), n (%) | Short cycle prevalence ratio† | 95% C1 | Long cycle (≥33 days), n (%) | Long cycle prevalence ratio† | 95% CI | |
|---|---|---|---|---|---|---|
| Age (years) | ||||||
| <25 | 29 (7.1) | 1.00 | (reference) | 32 (7.9) | 1.00 | (reference) |
| 25–29 | 68 (7.5) | 1.03 | 0.65–1.65 | 71 (7.8) | 1.02 | 0.65–1.59 |
| 30–34 | 32 (7.9) | 0.99 | 0.57–1.73 | 20 (4.9) | 0.64 | 0.35–1.16 |
| 35–40 | 10 (13.3) | 1.61 | 0.70–3.68 | 1 (1.3) | 0.17 | 0.02–1.31 |
| BMI (kg/m2) | ||||||
| <20 | 18 (6.6) | 0.88 | 0.52–1.51 | 16 (5.9) | 0.87 | 0.49–1.54 |
| 20–24 | 82 (8.0) | 1.00 | (reference) | 65 (6.3) | 1.00 | (reference) |
| 25–29 | 22 (6.7) | 0.85 | 0.52–1.40 | 25 (7.6) | 1.17 | 0.72–1.90 |
| ≥30 | 17 (10.3) | 1.52 | 0.86–2.69 | 18 (10.9) | 1.86 | 1.05–3.28 |
| Physical activity (METs) | ||||||
| <5 | 6 (9.5) | 1.08 | 0.44–2.70 | 3 (4.8) | 0.66 | 0.19–2.23 |
| 5–9 | 8 (5.7) | 0.70 | 0.32–1.52 | 10 (7.1) | 1.02 | 0.49–2.11 |
| 10–19 | 35 (6.8) | 0.87 | 0.55–1.36 | 44 (8.6) | 1.37 | 0.88–2.14 |
| 20–39 | 56 (7.9) | 1.00 | (reference) | 44 (6.2) | 1.00 | (reference) |
| ≥40 | 34 (9.2) | 1.21 | 0.77–1.90 | 23 (6.2) | 1.01 | 0.60–1.72 |
| Alcohol (drinks/week) | ||||||
| Does not drink | 34 (6.7) | 1.00 | (reference) | 35 (6.9) | 1.00 | (reference) |
| 1–2 | 41 (7.8) | 1.20 | 0.74–1.93 | 41 (7.9) | 1.15 | 0.71–1.86 |
| 3–6 | 45 (8.1) | 1.21 | 0.75–1.95 | 39 (7.1) | 1.11 | 0.68–1.82 |
| 7–13 | 17 (9.9) | 1.50 | 0.79–2.82 | 8 (4.7) | 0.72 | 0.32–1.61 |
| ≥14 | 2 (5.6) | 0.67 | 0.15–3.03 | 1 (2.8) | 0.41 | 0.05–3.12 |
| Smoking (cigarettes/day) | ||||||
| Does not smoke | 114 (7.8) | 1.00 | (reference) | 102 (6.9) | 1.00 | (reference) |
| <1 | 3 (2.9) | 0.32 | 0.10–1.03 | 8 (7.6) | 1.06 | 0.49–2.28 |
| 1–9 | 8 (8.6) | 1.02 | 0.47–2.22 | 5 (5.4) | 0.68 | 0.26–1.76 |
| ≥10 | 14 (11.1) | 1.40 | 0.75–2.59 | 9 (7.1) | 0.97 | 0.46–2.03 |
| Caffeine (mg/day) | ||||||
| <100 | 71 (6.9) | 1.00 | (reference) | 76 (7.4) | 1.00 | (reference) |
| 100–199 | 30 (7.8) | 1.10 | 0.70–1.74 | 21 (5.4) | 0.78 | 0.47–1.30 |
| 200–299 | 21 (10.3) | 1.50 | 0.87–2.59 | 16 (7.9) | 1.38 | 0.77–2.49 |
| ≥300 | 17 (9.9) | 1.36 | 0.74–2.51 | 11 (6.4) | 1.16 | 0.58–2.33 |
Notes:
*
We excluded women with missing covariate information (n = 147);
†
mutually adjusted for all other covariates and most recent method of birth control.
Abbreviations: n, number; CI, confidence interval; BMI, body mass index; METs, metabolic equivalents.