Table 1.

Frequency distributions for APOE group, childhood and midlife SEP, educational attainment, and mean NART and ACE-III scores (for 1762 participants with ACE-III data)

Variable	n (%)
APOE
No ε4	1076 (61.1)
Heterozygous ε4	388 (21.0)
Homozygous ε4	48 (2.7)
Missing	250 (14.2)
Father’s social class
Professional	134 (7.6)
Managerial	372 (21.1)
Intermediate	296 (16.8)
Skilled manual	519 (29.4)
Semiskilled	271 (15.4)
Unskilled	79 (4.5)
Missing	91 (5.2)
Mother’s education
Primary only	1151 (65.3)
Secondary or any formal qualifications	421 (23.9)
Missing	611 (10.8)
Educational attainment (by age 43)
No qualifications	403 (22.9)
Vocational only	235 (13.3)
Ordinary (‘O’) level	340 (19.3)
Advanced (‘A’) level	497 (28.2)
Higher	2.73 (15.5)
Missing	14 (0.8)
NS-SEC occupation (by age 53)*
1	221 (12.5)
2	504 (28.6)
3	307 (17.4)
4	200 (11.4)
5	120 (6.8)
6	228(12.9)
7	154 (8.7)
Missing	28 (1.6)

	Mean (SE)
NART	35.6 (0.22)
ACE-III	91.52 (0.14)

1, higher managerial, administrative and professional occupations; 2, lower managerial, administrative and professional occupations; 3, intermediate occupations; 4, small employers and own account workers; 5, lower supervisory and technical occupations; 6, semiroutine occupations; 7, routine occupations.

ACE-III, Addenbrooke’s Cognitive Examination third edition; APOE, apolipoprotein E; NART, National Adult Reading Test; NS-SEC, National Statistics Socio-Economic Classification; SEP, socioeconomic position.