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Table 1 Sample characteristics in total sample and according to education groups

From: Contribution of IQ in young adulthood to the associations of education and occupation with cognitive ability in older age

  Total sample ISCED 1/2 ISCED 3/4 ISCED 5/6
N (% of total sample) 623 94 (15.1%) 262 (42.1%) 267 (42.9%)
Age (years), mean ± SD 72.1 ± 4.9 72.5 ± 5.3 72.4 ± 4.7 71.7 ± 4.9
Male, n (%) 363 (58.3%) 49 (52.1%) 124 (47.3%) 190 (71.2%)
Geriatric Depression Scale*, median (interquartile range) 1 (0–3) 1 (1–2) 1 (0–3) 1 (0–2)
Occupation
 Semi−/unskilled, n (%) 57 (9.1%) 21 (22.3%) 27 (10.3%) 9 (3.4%)
 Skilled manual, n (%) 114 (18.3%) 28 (29.8%) 68 (26.0%) 18 (6.7%)
 Skilled non-manual, n (%) 224 (36.0%) 35 (37.2%) 125 (47.7%) 64 (24.0%)
 Managerial, n (%) 61 (9.8%) 8 (8.5%) 20 (7.6%) 33 (12.4%)
 Professional, n (%) 167 (26.8%) 2 (2.1%) 22 (8.4%) 143 (53.6%)
Pre-morbid IQ, mean ± SD 112.0 ± 14.3 101.6 ± 14.1 109.3 ± 13.6 118.4 ± 11.9
G**, mean ± SD 0.06 ± 1.00 − 0.27 ± 1.03 − 0.14 ± 0.98 0.38 ± 0.93
  1. ISCED International Standard Classification of Education, SD standard deviation. *n = 581 with data. **g was standardized on the full BioCog cohort