Participant characteristics
| All participants | N=420 | ||
| β-amyloid-positive | β-amyloid-negative | ||
| N | 460 | 77 | 343 |
| Sex, % female | 49 | 44 | 51 |
| Age at assessment, mean (SD) (range) | 70.7 (0.70) (69.2 to 71.8) | 70.6 (0.7) (69.4 to 71.8) | 70.6 (0.7) (69.2 to 71.8) |
| MMSE, mean (SD) (range)* | 29.3 (0.89) (26 to 30) | 29.1 (1.0) (26 to 30) | 29.3 (0.9) (26 to 30) |
| PACC, z-score, mean (SD) (range)* | −0.05 (0.68) (−2.43 to 1.72) | −0.10 (0.73) (−2.10 to 1.31) | 0.08 (0.66) (-2.43 to 1.72) |
| Highest education qualification, % | |||
| None | 16.2 | 16.9 | 16.1 |
| Below O-levels (vocational) | 5.0 | 6.5 | 4.3 |
| O-levels or equivalent | 24.8 | 24.7 | 25.5 |
| A-levels or equivalent | 36.3 | 33.8 | 36.5 |
| Degree or equivalent | 17.8 | 18.2 | 17.9 |
| Childhood cognitive ability mean (SD) (range)† | 0.39 (0.74) (−1.60 to 2.50) | 0.41 (0.74) (−1.59 to 2.47) | 0.44 (0.74) (−1.37 to 2.50) |
| Adult socioeconomic position, % | |||
| Unskilled | 1.0 | 1.3 | 0.6 |
| Partially unskilled | 4.8 | 3.9 | 5.4 |
| Skilled manual | 9.6 | 9.1 | 9.3 |
| Skilled non-manual | 21.5 | 16.9 | 22.0 |
| Intermediate | 52.0 | 53.3 | 51.9 |
| Professional | 11.3 | 15.6 | 10.5 |
| APOE status, % ε4-carrier‡§ | 30.1 | 59.7 | 23.2 |
| SCD questions | |||
| Perceive memory or cognitive difficulties (% yes) | 44.8 | 49.4 | 45.2 |
| Perceive decline in cognition or memory over past 2 years (% yes) | 45.4 | 50.6 | 45.5 |
| Difficulties or decline worse than peers (% yes) | 8.8¶ | 12.8** | 8.2†† |
| Would seek medical advice (% yes) | 2.3¶ | 6.4** | 1.5†† |
| SCD age onset, mean (SD) (range) | 63.2 (10.3) (20 to 70) ¶ | 63.6 (10.2) (20 to 70)** | 62.9 (10.7) (20 to 70)†† |
| SCD ≥60 years, % | 93.0 | 90.9 | 93.3 |
| Total MyCog score (out of 24): mean (SD) (range)* | 4.4 (3.9) (0 to 23) | 5.2 (3.6) (0 to 15) | 4.3 (3.9) (0 to 23) |
| AD8, mean (SD) (range)‡‡ | 0.2 (0.6) (0 to 5) | 0.4 (1.0) (0 to 5) | 0.1 (0.4) (0 to 3) |
| AD8, % AD8 ≥2* | 4.1 | 10.4 | 2.6 |
| Trait anxiety, mean (SD) (range) | 31.8 (7.9) (20 to 65) | 31.1 (8.0) (20 to 65) | 31.9 (7.8) (20 to 64) |
| State anxiety, mean (SD) (range) | 29.6 (7.9) (20 to 61) | 29.3 (7.1) (20 to 52) | 29.8 (8.1) (20 to 61) |
| Mental health disorder prevalence at age 69, % yes§§ | 7.0 | 10.4 | 6.2 |
| Family history of dementia, % yes* ¶¶ | 23.9 | 33.8 | 22.5 |
*The difference between the amyloid groups for this variable was significant at p<0.05.
†Z-scores for childhood cognitive ability were based on the full National Survey of Health and Development cohort of n=5362, so the mean for Insight 46 participants indicates that they had higher childhood cognitive ability on average than their peers not recruited to this substudy.
‡The difference between the amyloid groups for this variable was significant at p<0.01.
§n=458 (the participants that had APOE status information available).
¶n=260 (the participants who answered ‘yes’ either to perceiving memory or cognitive difficulties or decline in cognition or memory in the last 2 years).
**n=47 (the participants who answered ‘yes’ either to perceiving memory or cognitive difficulties or decline in cognition or memory in the last 2 years).
††n=195 (the participants who answered ‘yes’ either to perceiving memory or cognitive difficulties or decline in memory or cognition in the last 2 years).
‡‡n=459 (one informant questionnaire was not completed).
§§n=452 (the participants that completed the GHQ-28 questionnaire).
¶¶Of these participants with a family history, their affected relatives were: mother=70.0%, mean age at onset (SD): 82.2 (9.1) years; father=28.2%, 78.5 (8.8) years; siblings=8.2%, 75.5 (10.0) years (percentages do not add up to 100% as some people had multiple relatives with a family history of dementia).
GHQ, General Health Questionnaire; MMSE, Mini Mental State Examination; PACC, Preclinical Alzheimer Cognitive Composite; SCD, subjective cognitive decline.