Table 2.
Relative risks (RRs) with 95% confidence intervals (95% CIs) of adequate maternal periconceptional folic acid supplement use (before and during pregnancy) by paternal characteristics, in 683,785 births, Norway, 1999–2010
| Folic acid supplementation use | Unadjusted | Adjusted for paternal factors a b | Further adjusted for maternal factors a c | |||||
|---|---|---|---|---|---|---|---|---|
| Characteristics | Yes | No | RR* | 95% CI | RR* | 95% CI | RR* | 95% CI |
| Paternal age (years) | ||||||||
| < 20 | 86 | 4315 | 0.11 | 0.09–0.13 | 0.10 | 0.08–0.13 | 0.35 | 0.28–0.43 |
| 20–24 | 3325 | 45,123 | 0.37 | 0.36–0.39 | 0.37 | 0.36–0.38 | 0.68 | 0.66–0.71 |
| 25–29 | 22,886 | 139,785 | 0.76 | 0.75–0.78 | 0.77 | 0.76–0.79 | 0.94 | 0.93–0.96 |
| 30–34 | 43,348 | 192,053 | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference |
| 35–39 | 28,488 | 123,052 | 1.02 | 1.01–1.03 | 0.97 | 0.96–0.99 | 0.90 | 0.89–0.91 |
| 40+ | 12,733 | 68,591 | 0.85 | 0.83–0.87 | 0.80 | 0.78–0.81 | 0.72 | 0.71–0.74 |
| Paternal education | ||||||||
| Compulsory (1–10 years) | 11,694 | 119,259 | 0.40 | 0.39–0.40 | 0.52 | 0.51–0.53 | 0.69 | 0.68–0.71 |
| Intermediate (11–13 years) | 45,411 | 256,973 | 0.67 | 0.66–0.67 | 0.75 | 0.74–0.76 | 0.87 | 0.85–0.88 |
| Tertiary (14–20 years) | 51,894 | 177,924 | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference |
| Missing data | 1867 | 18,763 | ||||||
| Paternal occupational class d | ||||||||
| I Higher professionals | 19,957 | 66,678 | 1.05 | 1.04–1.07 | 1.05 | 1.03–1.06 | ||
| II Lower professionals | 33,366 | 119,415 | 1.00 | Reference | 1.00 | Reference | ||
| IIIa Higher routine | 12,292 | 65,248 | 0.73 | 0.71–0.74 | 0.89 | 0.88–0.91 | ||
| IIIb Lower routine | 5352 | 34,718 | 0.61 | 0.59–0.63 | 0.85 | 0.83–0.87 | ||
| IV Other self-employed workers | 60 | 298 | 0.77 | 0.61–0.97 | 0.83 | 0.65–1.05 | ||
| V Technicians | 836 | 4714 | 0.69 | 0.65–0.74 | 0.89 | 0.84–0.95 | ||
| VI Skilled | 15,174 | 93,581 | 0.64 | 0.63–0.65 | 0.84 | 0.83–0.86 | ||
| VII Semiskilled and unskilled | 11,643 | 99,941 | 0.48 | 0.47–0.49 | 0.75 | 0.73–0.76 | ||
| VIIb Agricultural | 908 | 6755 | 0.54 | 0.51–0.58 | 0.73 | 0.69–0.78 | ||
| Unclassified | 7575 | 45,249 | 0.66 | 0.64–0.67 | 0.96 | 0.94–0.99 | ||
| Missing data | 3703 | 36,322 | ||||||
| Paternal country of origin e | ||||||||
| Norway | 99,339 | 475,263 | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference |
| High income countries | 6535 | 26,952 | 1.13 | 1.10–1.16 | 1.06 | 1.04–1.09 | 1.06 | 1.03–1.08 |
| Low-middle-income countries | 4975 | 70,522 | 0.38 | 0.37–0.39 | 0.35 | 0.34–0.36 | 0.58 | 0.56–0.60 |
| Missing data | 17 | 182 | ||||||
aAll RRs for adequate folic acid supplementation adjusted for year of childbirth (continuous)
bRRs by paternal age, no other adjustment for paternal factors; RRs by paternal education adjusted for paternal age (< 20, 20–24, 25–29, 30–34, 35–39, 40+), paternal country of origin (Norway, high-income countries, low/middle-income countries); RRs by paternal occupation adjusted for paternal age, fathers country of origin, fathers education (compulsory, intermediate, tertiary); and RR by paternal origin of country, no other adjustment for paternal factors
cRRs by paternal age, further adjusted for maternal age (< 20, 20–24, 25–29, 30–34, 35–39, 40+); RRs by paternal education, further adjusted for maternal education (compulsory, intermediate, tertiary); RRs by paternal occupation, no further adjustment for maternal factors; RRs by paternal country of origin adjusted for maternal country of origin (Norway, High-income countries, Low/middle-income countries)
dCategorized according to the class scheme of Erikson, Goldthorpe and Portocarero (EGP) [33]
eCategorized according to the classification by World Health Organization, Health statistics and information systems, Estimates for 2000–2012 [34]
*p-value for difference between categories of paternal characteristics was < 0.001 using likelihood ratio test