Table 1.
Descriptive statistics for the study sample (n = 3433)a
| Observed N (% missing) | Observed % | Imputed % | Observed mean (SD) | Imputed mean (SD) | |
|---|---|---|---|---|---|
| Retirement age | 3433 (0%) | 61.2 (4.6) | 61.2 (4.6) | ||
| Verbal memory | 3433 (0%) | 6.9 (2.3) | 6.9 (2.3) | ||
| Abstract reasoning | 3433 (0%) | 45.4 (11.0) | 45.4 (11.0) | ||
| Phonemic verbal fluency | 3433 (0%) | 16.0 (3.9) | 16.0 (3.9) | ||
| Semantic verbal fluency | 3433 (0%) | 16.3 (4.1) | 16.3 (4.1) | ||
| Birth year | 3433 (0%) | 1943.7 (5.0) | 1943.7 (5.0) | ||
| Gender | 3433 (0%) | ||||
| Men | 72.2 | 72.2 | |||
| Highest education qualification | 3323 (3.2%) | ||||
| O level or lower | 41.7 | 42.0 | |||
| A level or equivalent | 24.8 | 24.7 | |||
| Degree level or higher | 33.5 | 33.3 | |||
| Employment grade | 3433 (0%) | ||||
| Clerical/support (lowest) | 12.1 | 12.1 | |||
| Professional/executive | 42.2 | 42.2 | |||
| Administrative (highest) | 45.7 | 45.7 | |||
| Still in civil service | 3400 (1.0%) | 62.0 | 62.1 | ||
| Job demand | 3433 (0%) | ||||
| Low | 24.4 | 24.4 | |||
| Middle | 46.2 | 46.2 | |||
| High | 29.4 | 29.4 | |||
| Job decision latitude | 3433 (0%) | ||||
| Low | 24.8 | 24.8 | |||
| Middle | 31.7 | 31.7 | |||
| High | 43.5 | 43.5 | |||
| Spouse’s employment status | 3341(2.7%) | ||||
| Working spouse | 50.3 | 50.1 | |||
| Non-working spouse | 28.3 | 28.3 | |||
| No spouse | 21.4 | 21.6 | |||
| Smoking status | 3312 (3.5%) | ||||
| Never-smoker | 49.0 | 48.9 | |||
| Ex-smoker | 41.6 | 41.8 | |||
| Current smoker | 9.4 | 9.3 | |||
| Alcohol consumption | 3293 (4.1%) | ||||
| None last week | 15.0 | 15.1 | |||
| ≤ 10 units last week | 42.1 | 42.0 | |||
| > 10 units last week | 42.9 | 42.9 | |||
| GHQ depression (≥ 4) | 3300 (3.9%) | ||||
| Yes | 11.4 | 11.5 | |||
| BMIb | 3068 (10.6%) | 26.6 (4.2) | 26.7 (4.2) | ||
| Normal (< 25 kg/m2) | 37.5 | 37.2 | |||
| Overweight (25–29.9 kg/m2) | 44.4 | 44.3 | |||
| Obese (≥ 30 kg/m2) | 18.1 | 18.5 | |||
| Blood pressureb | 3232 (5.9%) | 124.6 (16.0)c | 124.7 (16.0)c | ||
| High (≥ 140/90 mmHg) | 18.7 | 18.9 | 75.0 (10.7)d | 75.1 (10.7)d | |
| Blood cholesterolb | 3200 (6.8%) | 5.7 (1.0) | 5.7 (1.0) | ||
| High (≥ 5 mmol/l) | 77.0 | 77.1 | |||
| CHD | 3433 (0%) | 7.5 | 7.5 | ||
| Stroke | 3433 (0%) | 0.3 | 0.3 | ||
| Cancer | 3400 (0.1%) | 3.5 | 3.5 | ||
| Diabetes | 3433 (0%) | 21.6 | 21.6 |
aInformation for the cognitive outcomes and time-varying covariates (smoking status, alcohol consumption, GHQ depression, BMI, blood pressure, blood cholesterol, CHD, stroke, cancer, diabetes) were based on the last interview before retirement
bBMI, blood pressure, and blood cholesterol were used as continuous variables in regression models
cMean (SD) for systolic blood pressure
dMean (SD) for diastolic blood pressure