Table 1:
Sample characteristics for 1549 incident cases of schizophrenia and 1549 individually age- and sex-matched controls
| Characteristic | Cases N (%) |
Controls N (%) |
Incidence rate ratio1 IRR (95% CI) |
|||
|---|---|---|---|---|---|---|
| Sex | ||||||
| Male | 859 | (55.46) | 859 | (55.46) | - | |
| Female | 690 | (44.54) | 690 | (44.54) | - | |
| Age at matching, median (IQR) | 20 | (3.9) | 20 | (3.9) | - | |
| Polygenic risk score2, mean (SD) | 0.05 | (0.88) | ‒0.23 | (0.84) | 1.46 | (1.34,1.61) |
| Parental history of mental disorders | ||||||
| Schizophrenia or bipolar disorder | 107 | (6.91) | 39 | (2.52) | 3.23 | (2.24,4.77) |
| Other mental disorders | 355 | (22.92) | 167 | (10.78) | 2.60 | (2.12,3.21) |
| None | 1087 | (70.17) | 1343 | (86.70) | 1.00 | (ref) |
| Urbanicity of place of birth3 | ||||||
| Capital (Copenhagen) | 218 | (14.07) | 163 | (10.52) | 1.67 | (1.31,2.15) |
| Suburb of the capital | 249 | (16.07) | 221 | (14.27) | 1.38 | (1.10,1.73) |
| Provincial cities | 174 | (11.23) | 180 | (11.62) | 1.18 | (0.93,1.50) |
| Provincial towns | 436 | (28.15) | 414 | (26.73) | 1.28 | (1.06,1.54) |
| Rural areas | 472 | (30.47) | 571 | (36.86) | 1.00 | (ref) |
| Urbanicity of residence at age 154 | ||||||
| Capital (Copenhagen) | 148 | (10.16) | 103 | (7.07) | 1.58 | (1.20,2.09) |
| Suburb of the capital | 216 | (14.84) | 220 | (15.11) | 1.10 | (0.88,1.38) |
| Provincial cities | 143 | (9.82) | 147 | (10.10) | 1.08 | (0.84,1.40) |
| Provincial towns | 422 | (28.98) | 392 | (26.92) | 1.20 | (1.00,1.44) |
| Rural areas | 523 | (35.92) | 584 | (40.11) | 1.00 | (ref) |
| Greenland or other countries | 4 | (0.28) | 10 | (0.69) | 0.47 | (0.13,1.42) |
| Parental place of birth | ||||||
| Both parents born in Denmark | 1355 | (87.48) | 1431 | (92.38) | 1.00 | (ref) |
| One parent born in Denmark | 154 | (9.94) | 90 | (5.81) | 1.83 | (1.39,2.42) |
| Other5 | 40 | (2.58) | 28 | (1.81) | 1.47 | (0.91,2.43) |
| Paternal age at childbirth | ||||||
| 20 years or younger | 53 | (3.42) | 44 | (2.84) | 1.36 | (0.90,2.07) |
| 21–25 years | 305 | (19.69) | 260 | (16.79) | 1.32 | (1.07,1.62) |
| 26–30 years | 520 | (33.57) | 580 | (37.44) | 1.00 | (ref) |
| 31–35 years | 377 | (24.34) | 413 | (26.66) | 1.03 | (0.85,1.23) |
| 36–40 years | 186 | (12.01) | 168 | (10.85) | 1.23 | (0.97,1.56) |
| 41 years or older | 84 | (5.42) | 72 | (4.65) | 1.34 | (0.95,1.88) |
| Missing | 24 | (1.55) | 12 | (0.77) | 2.30 | (1.16,4.82) |
1
IRRs are adjusted for age, sex, and date of birth by design
2
Normalized to the sample
3
Provincial cities = municipalities having a town with more than 100,000 inhabitants; provincial towns= municipalities having a town with between 10,000 and 100,000 inhabitants; rural areas= other municipalities in Denmark (largest town has less than 10,000 inhabitants).
4
Only pairs whose date of matching (case onset) is after the 15th birthday (1 456 pairs).
5
Both parents born abroad, in Greenland or missing.