Table 1.
Characteristics of the study population
| Participants (n=607) |
Day shifts (n=305) |
Day–night shifts (n=302) |
|
| Age (years), median (IQR) | 37 (31–42) | 37 (32–43) | 36 (30–42) |
| Country of origin, n | 605 | 303 | 302 |
| Zimbabwe, n (%) | 378 (62.5) | 188 (62.0) | 190 (62.9) |
| South Africa, n (%) | 122 (20.2) | 60 (19.8) | 62 (20.5) |
| Zambia, n (%) | 45 (7.4) | 24 (7.9) | 21 (7.0) |
| Other, n (%) | 60 (9.9) | 31 (10.2) | 29 (9.6) |
| Working as driver (years), median (IQR) | 9 (5–14) | 9 (5–14) | 8 (5–14) |
| Time spent working per month (days), median (IQR) | 20 (15-24) | 20 (18–24) | 20 (15–24) |
| Time sleeping/day (hours), median (IQR) | 8 (6–9) | 8 (6–9) | 7.5 (6–9) |
| Education level, n | 585 | 287 | 298 |
| Primary school or less, n (%) | 51 (8.7) | 32 (11.1) | 19 (6.4) |
| Secondary school, n (%) | 322 (55.0) | 150 (52.3) | 172 (57.7) |
| Matrix/college/university, n (%) | 212 (36.2) | 105 (36.6) | 107 (35.9) |
| Marital status, n | 607 | 305 | 302 |
| Stable relationship, n (%) | 545 (89.8) | 278 (91.1) | 267 (88.4) |
| No relationship, n (%) | 62 (10.2) | 27 (8.9) | 35 (11.6) |
| HIV positive, n (%) | 54 (8.9) | 24 (7.9) | 30 (9.9) |
| Weekly leisure activity score, median (IQR) | 17 (0–27) | 17 (0–19) | 17 (0–31) |
| Body mass index (kg/m2), n | 597 | 298 | 299 |
| Body mass index <30 kg/cm2, n (%) | 428 (71.7) | 220 (73.8) | 208 (69.6) |
| Body mass index ≥30 kg/cm2, n (%) | 169 (28.3) | 78 (26.2) | 91 (30.4) |
| Waist to hip ratio, median (IQR) | 0.86 (0.81–0.91) | 0.87 (0.82–0.92) | 0.85 (0.80–0.91) |
| Neck circumference (cm), median (IQR) | 37 (36–39) | 37 (35–39) | 38 (36–40) |
| Smoking ever in life, n (%) | 90 (14.9) | 47 (15.6) | 43 (14.2) |
| Family history for CVD, n (%) | 32 (5.3) | 14 (4.7) | 18 (6.0) |
| Heart rate (bpm), median (IQR) | 75 (66–83) | 75 (68–83) | 75 (65–83) |
| Blood pressure classification, n | 594 | 297 | 297 |
| Normal, n (%) | 100 (16.8) | 43 (14.5) | 57 (19.2) |
| Prehypertension*, n (%) | 297 (50.0) | 159 (53.5) | 138 (46.5) |
| Hypertension† or Tx, n (%) | 197 (33.2) | 95 (32.0) | 102 (34.3) |
| Serum glucose, n | 457 | 234 | 223 |
| ≥7.8 mmol/L or Tx, n (%) | 38 (8.3) | 18 (7.7) | 20 (9.0) |
| <7.8 mmol/L, n (%) | 419 (91.7) | 216 (92.3) | 203 (91.0) |
| Serum creatinine | 586 | 296 | 290 |
| ≥110 mmol/L, n (%) | 102 (17.4) | 58 (19.6) | 44 (15.2) |
| <110 mmol/L, n (%) | 484 (82.6) | 238 (80.4) | 246 (84.8) |
| eGFR‡ | 586 | 296 | 290 |
| ≥90 mL/min/1.73 m2, n (%) | 440 (75.1) | 212 (71.6) | 228 (78.6) |
| 60–90 mL/min/1.73 m2, n (%) | 139 (23.7) | 80 (27.0) | 59 (20.3) |
| <60 mL/min/1.73 m2, n (%) | 7 (1.2) | 4 (1.4) | 3 (1.1) |
| Total cholesterol | 587 | 296 | 291 |
| ≥5.17 mmol/L, n (%) | 140 (23.9) | 77 (26.0) | 63 (21.6) |
| <5.17 mmol/L, n (%) | 447 (76.1) | 219 (74.0) | 228 (78.4) |
| HDL cholesterol | 587 | 296 | 291 |
| ≤1.04 mmol/L, n (%) | 151 (25.7) | 79 (26.7) | 72 (24.7) |
| >1.04 mmol/L, n (%) | 436 (74.3) | 217 (73.3) | 219 (75.3) |
| LDL cholesterol | 587 | 296 | 291 |
| ≥3.0 mmol/L, n (%) | 217 (37.0) | 113 (38.2) | 104 (35.7) |
| <3.0 mmol/L, n (%) | 370 (63.0) | 183 (61.8) | 187 (64.3) |
| Triglycerides | 587 | 296 | 291 |
| ≥1.7 mmol/L, n (%) | 211 (35.9) | 116 (39.2) | 95 (32.6) |
| <1.7 mmol/L, n (%) | 376 (64.1) | 180 (60.8) | 196 (67.4) |
*Systolic blood pressure >120 mm Hg and/or diastolic blood pressure >80 mm Hg.
†Systolic blood pressure >140 mm Hg and/or diastolic blood pressure >90 mm Hg.
‡Calculated using: 186 × (creatinine/88.4)−1.154 x (age)−0.203 × (0.742 if female) × (1.210 if black African).
bpm, beats per minute; CVD, cardiovascular disease; eGFR, estimated glomerular filtration rate; HDL, high-density lipoprotein; LDL, low-density lipoprotein; Tx, on medication.