Table 1 Descriptive characteristics of the study participants and stratified by major depressive disorder (MDD) status at follow-up
Variables | Total (n=354,897) | Individuals without MDD (n=340,187) | Individuals with MDD (n=14,710) |
|---|---|---|---|
Age, years (mean ± SD) | 56.71 ± 8.07 | 56.71 ± 8.07 | 56.87 ± 8.08 |
Gender, n (%) | |||
 Female | 189,358 (53.4) | 179,981 (52.9) | 9377 (63.7) |
 Male | 165,539 (46.6) | 160,206 (47.1) | 5333 (36.3) |
Ethnicity, n (%) | |||
 White ethnicity | 340,408 (96.3) | 326,236 (96.3) | 14,172 (96.9) |
 Mixed ethnicity | 1600 (0.5) | 1519 (0.4) | 81 (0.6) |
 Asian ethnicity | 5131 (1.5) | 4966 (1.5) | 165 (1.1) |
 Black ethnicity | 3105 (0.9) | 3014 (0.9) | 91 (0.6) |
 Chinese ethnicity | 783 (0.2) | 775 (0.2) | 8 (0.1) |
 Other ethnicities | 2322 (0.7) | 2214 (0.7) | 108 (0.7) |
 Missing data | 1548 (0.4) | 1463 (0.4) | 85 (0.6) |
Education level, n (%) | |||
 College or university degree | 111,478 (31.8) | 108,187 (32.2) | 3291 (22.8) |
 A/AS levels or equivalent | 39,041 (11.1) | 37,616 (11.2) | 1425 (9.9) |
 O level/GCSE or equivalent | 77,115 (22.0) | 73,973 (22.0) | 3142 (21.8) |
 CSE or equivalent | 20,170 (5.8) | 19,148 (5.7) | 1022 (7.1) |
 NVQ or HND or HNC or equivalent | 23,484 (6.7) | 22,381 (6.7) | 1103 (7.6) |
 Other professional qualifications | 18,141 (5.2) | 17,385 (5.2) | 756 (5.2) |
 None of the above | 60,991 (17.4) | 57,287 (17.1) | 3704 (25.6) |
 Missing data | 4477 (1.3) | 4210 (1.2) | 267 (1.8) |
Employment status, n (%) | |||
 Employed | 203,737 (58.0) | 197,160 (58.5) | 6577 (45.3) |
 Retired | 120,405 (34.3) | 115,095 (34.2) | 5310 (36.6) |
 Unemployed, home maker, or others | 27,126 (7.7) | 24,506 (7.3) | 2620 (18.1) |
 Missing data | 3629 (1.0) | 3426 (1.0) | 203 (1.4) |
Household income, n (%) | |||
 Less than £31,000 | 143,987 (47.7) | 136,113 (46.9) | 7874 (65.3) |
 £31,000 and above | 157,996 (52.3) | 153,806 (53.1) | 4190 (34.7) |
 Missing data | 52,914 (14.9) | 50,268 (14.8) | 2646 (18.0) |
Townsend deprivation index, (mean ± SD) | −1.46 ± 2.98 | −1.50 ± 2.96 | −0.65 ± 3.35 |
 Missing data | 369 (0.1) | 360 (0.11) | 9 (0.06) |
Healthy lifestyle factors, n (%) | |||
 Smoking | 34,974 (9.9) | 32,459 (9.6) | 2515 (17.2) |
 Alcohol intake | 74,074 (20.9) | 71,391 (21.0) | 2683 (18.3) |
 Physical activity | 55,686 (19.5) | 52,823 (19.2) | 2863 (26.1) |
 TV viewing | 102,308 (28.9) | 96,759 (28.5) | 5549 (37.8) |
 Sleep time | 93,612 (26.4) | 88,292 (26.0) | 5320 (36.2) |
 Fruit and vegetable intake | 63,882 (18.5) | 60,721 (18.4) | 3161 (22.5) |
 Oily fish intake | 156,756 (44.2) | 149,735 (44.1) | 7021 (47.8) |
 Red meat intake | 174,118 (49.7) | 167,380 (49.8) | 6738 (46.8) |
 Processed meat intake | 112,094 (31.6) | 107,355 (31.6) | 4739 (32.3) |
Lifestyle category, n (%) | |||
 More healthy | 152,734 (54.7) | 147,875 (55.1) | 4859 (46.2) |
 Moderately healthy | 117,865 (42.2) | 112,779 (42.0) | 5086 (48.3) |
 Least healthy | 8489 (3.0) | 7907 (2.9) | 582 (5.5) |
Genetic risk category, n (%) | |||
 Low | 118,478 (33.4) | 113,888 (33.5) | 4590 (31.2) |
 Intermediate | 118,295 (33.3) | 113,420 (33.3) | 4875 (33.1) |
 High | 118,124 (33.3) | 112,879 (33.2) | 5245 (35.7) |
Air pollution, μg/m3 (mean ± SD) | |||
 PM2.5 | 9.98 ± 1.06 | 9.97 ± 1.06 | 10.13 ± 1.09 |
 PM10 | 16.20 ± 1.90 | 16.20 ± 1.91 | 16.30 ± 1.88 |
 NO2 | 26.41 ± 7.59 | 26.37 ± 7.58 | 27.22 ± 7.65 |
 NOX | 43.68 ± 15.55 | 43.60 ± 15.52 | 45.53 ± 16.05 |