Table 1.
Age-standardized characteristics of premenstrual syndrome (PMS) cases and controls at 2–4 years prior to the reference year (n 3638); Nurses’ Health Study II PMS Sub-Study, 1991–2005
| Cases (n 1222) | Controls (n 2416) | ||||
|---|---|---|---|---|---|
| Characteristic* | Mean | sd | Mean | sd | P value† |
| Age (years) | 37·2 | 4·3 | 38·6 | 4·4 | <0·001 |
| BMI (kg/m2) | |||||
| At 2–4 years prior to reference year | 25·3 | 5·6 | 24·6 | 5·2 | <0·001 |
| At age 18 years | 21·4 | 3·3 | 21·1 | 3·1 | 0·02 |
| Age at menarche (years) | 12·4 | 1·4 | 12·5 | 1·4 | 0·04 |
| Age at first birth (years)‡ | 26·4 | 4·2 | 26·5 | 3·9 | 0·74 |
| Number of full-term pregnancies (≥6 months) | 1·9 | 1·2 | 1·9 | 1·2 | 0·40 |
| Physical activity (MET/week) | 28·5 | 95·8 | 24·6 | 65·3 | 0·06 |
| Pack-years of cigarette smoking | 8·6 | 65·2 | 5·0 | 50·4 | 0·07 |
| Alcohol intake (g/d) | 3·3 | 6·0 | 3·7 | 6·8 | 0·31 |
| Total energy intake (kJ/d) | 7594 | 2247 | 7640 | 2167 | 0·50 |
| Vitamin D intake from food sources (µg/d)§ | 5·9 | 2·8 | 6·1 | 3·1 | 0·02 |
| Total vitamin B6 intake (mg/d)§ | 9·9 | 28·7 | 6·8 | 19·1 | <0·001 |
| Total vitamin B12 intake (mg/d)§ | 11·2 | 18·9 | 10·9 | 19·9 | 0·19 |
| Total thiamin intake (mg/d)§ | 4·4 | 10·6 | 3·9 | 9·5 | 0·04 |
| Total riboflavin intake (mg/d)§ | 4·9 | 10·6 | 4·3 | 9·2 | 0·02 |
| Total Fe intake (mg/d)§ | 23·9 | 23·4 | 24·0 | 22·5 | 0·45 |
| Total Zn intake (mg/d) | 16·3 | 10·5 | 16·3 | 12·1 | 0·87 |
| Total K intake (mg/d) | 2996 | 542 | 2991 | 548 | 0·22 |
| Total Ca intake (mg/d)§ | 1054 | 449 | 1084 | 447 | 0·26 |
| % | % | ||||
| History of tubal ligation | 20 | 21 | 0·89 | ||
| Oral contraceptive use | |||||
| Ever | 86 | 79 | <0·001 | ||
| Current | 8 | 6 | 0·47 | ||
| Duration>4 years | 61 | 57 | 0·004 | ||
| Smoking status | |||||
| Current | 12 | 6 | <0·001 | ||
| Past | 28 | 18 | <0·001 | ||
| Previously diagnosed with depression | 18 | 8 | <0·001 | ||
| Previously used antidepressant medication | 15 | 7 | <0·001 | ||
| History of childhood trauma | 17 | 9 | <0·001 | ||
MET, metabolic equivalent of task.
*
All characteristics, except age, are standardized to the age distribution of participants at 2–4 years prior to the reference year.
†
Calculated using generalized linear model.
‡
Limited to parous women.
§
Energy-adjusted value.