Table 2.
Multivariable-adjusted odds ratios of lifetime depression a among participants in Nurses’ Health Study and Nurses’ Health Study II across quintiles of total photoperiod and extreme differences in photoperiod during maternal pregnancy
| QUINTILES OF TOTAL PHOTOPERIOD DURING MATERNAL PREGNANCY | ||||||
|---|---|---|---|---|---|---|
| Nurses’ Health Study (n=78,308) | ||||||
| Median values | Quintile 1 (3,209 hours) | Quintile 2 (3,295 hours) | Quintile 3 (3,419 hours) | Quintile 4 (3,542 hours) | Quintile 5 (3,630 hours) | p-trend |
| Cases of depression (%) | 2,064 (13.18%) | 2,090 (13.34%) | 2,050 (13.09%) | 1,954 (12.48%) | 2,012 (12.85%) | |
| Multivariable-adjusted OR, 95% CI b | 1.00 (ref) | 1.02 (0.96, 1.09) | 1.00 (0.93, 1.07) | 0.94 (0.88, 1.01) | 0.97 (0.91, 1.03) | 0.04 |
| Nurses’ Health Study II (n=82,429) | ||||||
| Median values | Quintile 1 (3,214 hours) | Quintile 2 (3,298 hours) | Quintile 3 (3,418 hours) | Quintile 4 (3,537 hours) | Quintile 5 (3,625 hours) | p-trend |
| Cases of depression (%) | 3,565 (21.63%) | 3,565 (21.62%) | 3,620 (21.96%) | 3,662 (22.21%) | 3,598 (21.82%) | |
| Multivariable-adjusted OR, 95% CI b | 1.00 (ref) | 1.01 (0.96, 1.07) | 1.03 (0.97, 1.08) | 1.05 (0.99, 1.10) | 1.02 (0.96, 1.07) | 0.26 |
| Combined cohorts (n=160,737) | ||||||
| Median values | Quintile 1 (3,211 hours) | Quintile 2 (3,297 hours) | Quintile 3 (3,419 hours) | Quintile 4 (3,540 hours) | Quintile 5 (3,628 hours) | p-trend |
| Cases of depression (%) | 5,607 (17.44%) | 5,677 (17.66%) | 5,682 (17.68%) | 5,698 (17.72%) | 5,516 (17.16%) | |
| Multivariable-adjusted OR, 95% CI b | 1.00 (ref) | 1.01 (0.97, 1.05) | 1.01 (0.97, 1.05) | 1.01 (0.97, 1.05) | 0.99 (0.95, 1.03) | 0.58 |
| QUINTILES OF EXTREME DIFFERENCES IN PHOTOPERIOD DURING MATERNAL PREGNANCY | ||||||
| Nurses’ Health Study (n=78,308) | ||||||
| Median values | Quintile 1 (4.97 hours) | Quintile 2 (5.57 hours) | Quintile 3 (5.78 hours) | Quintile 4 (5.98 hours) | Quintile 5 (6.20 hours) | p-trend |
| Cases of depression (%) | 2,111 (13.48%) | 2,116 (13.51%) | 2,066 (13.15%) | 1,958 (12.49%) | 1,919 (12.30%) | |
| Multivariable-adjusted OR, 95% CI b | 1.00 (ref) | 0.96 (0.90, 1.03) | 0.92 (0.86, 0.98) | 0.88 (0.82, 0.94) | 0.88 (0.83, 0.94) | <0.001 |
| Nurses’ Health Study II (n=82,429) | ||||||
| Median values | Quintile 1 (4.55 hours) | Quintile 2 (5.35 hours) | Quintile 3 (5.77 hours) | Quintile 4 (5.95 hours) | Quintile 5 (6.20 hours) | p-trend |
| Cases of depression (%) | 3,913 (23.74%) | 3,722 (22.57%) | 3,473 (21.05%) | 3,352 (20.35%) | 3,550 (21.54%) | |
| Multivariable-adjusted OR, 95% CI b | 1.00 (ref) | 0.92 (0.87, 0.97) | 0.86 (0.82, 0.91) | 0.80 (0.76, 0.84) | 0.85 (0.81, 0.89) | <0.001 |
| Combined cohorts (n=160,737) | ||||||
| Median values | Quintile 1 (4.70 hours) | Quintile 2 (5.45 hours) | Quintile 3 (5.78 hours) | Quintile 4 (5.97 hours) | Quintile 5 (6.20 hours) | p-trend |
| Cases of depression (%) | 6,283 (19.56%) | 5,848 (18.18%) | 5,623 (17.51%) | 5,112 (15.87%) | 5,314 (16.55%) | |
| Multivariable-adjusted OR, 95% CI b | 1.00 (ref) | 0.94 (0.91, 0.98) | 0.90 (0.86, 0.93) | 0.82 (0.79, 0.86) | 0.87 (0.84, 0.91) | <0.001 |
Abbreviations: CI=confidence interval; OR=odds ratio
Defined as cases with clinician-diagnosed depression and antidepressant medication use during follow up.
Models are adjusted for birth year (⩽1925, 1926–1930, 1931–1935, 1936–1940, ⩾1941 in NHS, and ⩽1945, 1946–1950, 1951–1955, ⩾1956 in NHS II), race (white, black, other), hair color (dark brown, light brown, black, blond, red, missing), parent’s home ownership at birth (yes, no, missing), mother’s occupation in childhood (professional/executive, sales/clerical, craftsman/service, laborer/farmer/military, stay at home parent, missing), father’s occupation in childhood (professional/executive, sales/clerical, craftsman/service, laborer/farmer/military, stay at home parent, missing), mother’s smoking status during pregnancy (yes, no, missing), birth weight (<5.5, 5.5–6.9, 7–8.4, 8.5+ pounds, missing), and breastfeeding (yes, no, missing).