Table 1.
Correlates of irregular menstrual periods among nulliparous Danish women enrolled in the Snart-Gravid study (n = 2,613*)
| Irregular period, n (%) | Prevalence ratio† | 95% CI | |
|---|---|---|---|
| Age (years) | |||
| <25 | 150 (27.0) | 1.00 | (reference) |
| 25–29 | 362 (28.5) | 1.06 | 0.90–1.25 |
| 30–34 | 97 (19.4) | 0.72 | 0.57–0.91 |
| 35–40 | 9 (10.7) | 0.39 | 0.21–0.74 |
| BMI (kg/m2) | |||
| <20 | 109 (28.5) | 1.09 | 0.91–1.30 |
| 20–24 | 347 (25.3) | 1.00 | (reference) |
| 25–29 | 94 (22.2) | 0.84 | 0.69–1.03 |
| ≥30 | 68 (29.2) | 1.09 | 0.87–1.35 |
| Physical activity (METs) | |||
| <5 | 37 (37.0) | 1.54 | 1.16–2.04 |
| 5–9 | 52 (27.1) | 1.08 | 0.84–1.40 |
| 10–19 | 200 (28.0) | 1.15 | 0.97–1.35 |
| 20–39 | 230 (24.6) | 1.00 | (reference) |
| ≥40 | 99 (21.1) | 0.83 | 0.68–1.02 |
| Alcohol (drinks/week) | |||
| Does not drink | 181 (26.3) | 1.00 | (reference) |
| 1–2 | 174 (24.8) | 0.95 | 0.79–1.13 |
| 3–6 | 183 (24.9) | 0.99 | 0.83–1.19 |
| 7–13 | 60 (26.0) | 1.09 | 0.85–1.41 |
| ≥14 | 20 (35.7) | 1.42 | 0.99–2.05 |
| Smoking (cigarettes/day) | |||
| Does not smoke | 520 (26.1) | 1.00 | (reference) |
| <1 | 40 (27.6) | 0.98 | 0.75–1.29 |
| 1–9 | 28 (23.1) | 0.85 | 0.61–1.18 |
| ≥10 | 30 (19.2) | 0.69 | 0.49–0.96 |
| Caffeine (mg/day) | |||
| <100 | 380 (26.9) | 1.00 | (reference) |
| 100–199 | 127 (24.8) | 0.97 | 0.81–1.15 |
| 200–299 | 57 (21.9) | 0.90 | 0.71–1.16 |
| ≥300 | 54 (23.9) | 1.05 | 0.82–1.36 |
Notes:
*
We excluded women with missing information on cycle regularity (n = 6) and missing covariate information (n = 196);
†
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.