Table 1.
Descriptive statistics of the 52 variables in the sample.
| Demographics | N | M | SD | Min | Max |
|---|---|---|---|---|---|
| Age | 9,979 | 67.01 | 9.18 | 50 | 98 |
| Gender (female) | 9,979 | 59.8% | |||
| Education (in years) | 9,963 | 13.27 | 2.61 | 0 | 17 |
| Race (African American) | 9,976 | 9.3% | |||
| Race (Other) | 9,976 | 3.5% | |||
| Ethnicity (Hispanic) | 9,979 | 6.2% | |||
| Income (in 1,000 USD) | 9,966 | 66.88 | 61.97 | 0 | 300 |
| Wealth (in 1,000 USD) | 9,966 | 554.19 | 816.91 | −769 | 5,060 |
| Marital status (married) | 9,978 | 67.3% | |||
| Work | 9,809 | 37.6% | |||
| Type home (assisted) | 9,811 | 0.6% | |||
| Psychosocial | N | M | SD | Min | Max |
| Conscientiousness | 9,895 | 3.41 | 0.45 | 1 | 4 |
| Openness | 9,877 | 2.99 | 0.53 | 1 | 4 |
| Extraversion | 9,908 | 3.26 | 0.53 | 1 | 4 |
| Agreeableness | 9,906 | 3.55 | 0.45 | 1 | 4 |
| Emotional distress (z) | 9,978 | −0.01 | 0.68 | −1.31 | 3.39 |
| Life satisfaction (z) | 9,857 | 0.06 | 0.98 | −2.82 | 1.67 |
| Positive affect (z) | 9,877 | 0.08 | 0.95 | −3.70 | 2.04 |
| Purpose in life | 9,821 | 4.70 | 0.90 | 1 | 6 |
| Optimism | 9,843 | 4.57 | 1.12 | 1 | 6 |
| Social contact | 7,213 | 3.72 | 0.76 | 1 | 6 |
| Health | N | M | SD | Min | Max |
| Subjective health | 9,972 | 3.35 | 1.02 | 1 | 5 |
| Childhood health | 6,765 | 4.23 | 0.94 | 1 | 5 |
| Hearing | 9,975 | 3.43 | 1.06 | 1 | 5 |
| Hear aid | 9,302 | 1.8% | |||
| Sleep medication | 9,975 | 19.8% | |||
| Childhood traumas | 9,901 | 0.34 | 0.60 | 0 | 3 |
| Lifetime traumas | 9,911 | 1.23 | 1.18 | 0 | 7 |
| BMI | 9,807 | 28.97 | 5.65 | 11.18 | 83.82 |
| Highest BMI ever | 9,908 | 30.82 | 6.55 | 11.33 | 49.71 |
| BMI slope | 9,979 | 0.00 | 0.99 | −3.59 | 3.58 |
| Waist circumference | 8,781 | 39.34 | 5.60 | 25.00 | 55.25 |
| Hypertension | 9,960 | 55.8% | |||
| Diabetes | 9,961 | 18.0% | |||
| Heart disease | 9,965 | 22.9% | |||
| Stroke | 9,966 | 4.9% | |||
| Cancer | 9,976 | 14.8%% | |||
| Alcohol | 9,965 | 56.3% | |||
| Mild activity | 9,963 | 93.7% | |||
| Moderate activity | 9,962 | 83.7% | |||
| Vigorous activity | 9,960 | 42.9% | |||
| Total activity | 9,966 | 96.6% | |||
| Smoking ever | 9,978 | 52.6% | |||
| Functional limitations | 8,920 | 2.14 | 2.43 | 0 | 10 |
| Grip strength | 7,802 | 32.12 | 10.82 | 0.50 | 60.50 |
| Biomarker/Polygenic | N | M | SD | Min | Max |
| Cholesterol | 7,802 | 203.24 | 41.69 | 89.04 | 405.41 |
| High Density Lipoprotein | 6,748 | 55.55 | 16.30 | 12.11 | 139.52 |
| Cystatin C | 7,820 | 0.00 | 0.13 | −0.64 | 0.98 |
| C Reactive Protein | 7,891 | 0.30 | 0.51 | −1.70 | 2.34 |
| Hemoglobin A1C | 8,119 | 5.81 | 0.90 | 4.07 | 14.79 |
| Polygenic score APOE without ε4 | 7,082 | −0.03 | 1.00 | −3.95 | 4.08 |
| Polygenic score APOE with ε4 | 7,082 | −0.03 | 1.00 | −3.95 | 4.07 |
| Cognitive Status | N | M | SD | Min | Max |
| Impairment | 3,119 (31.3%) | ||||
| Dementia | 622 (6.2%) | ||||
| Time-to-detection impairment | 9,979 | 6.85 | 2.76 | 2 | 10 |
| Time-to-detection dementia | 9,979 | 7.67 | 2.33 | 2 | 10 |
| Age at onset impairment | 9,979 | 73.86 | 8.70 | 52 | 101 |
| Age at onset dementia | 9,979 | 74.68 | 8.79 | 52 | 101 |
Note. N = number of participants; M = mean; SD = standard deviation. Data of 52 predictors were obtained in 2006 or 2008, respectively, except polygenic scores, which were obtained in 2013. Smoking refers to whether participants have ever smoked from 1992 to 2008. We included three variables of BMI: BMI at baseline, highest BMI ever and BMI slope. Given that there was no measure for midlife obesity in the data, highest BMI ever and BMI slope seemed the best possible alternatives. BMI slope was calculated using information from the earliest available measurement occasion in HRS - e.g., 1992 - until 2 years before year of detection of cognitive impairment/dementia or the last year of cognitive testing for unimpaired individuals. Emotional distress is an averaged factor consisting of standardized negative emotion variables (i.e., neuroticism, hostility, anxiety, negative affect, hopelessness, pessimism, depression, loneliness and perceived constraints). The items of life satisfaction were rated on a scale from 1–6 in 2006 and from 1–7 in 2008. Scores were thus standardized before combining them. For positive affect, participants rated 6 (in 2006) and 12 (in 2008) items. Scores were thus standardized before combining them. Time-to-detection (in years) refers to years from baseline to year in which onset of impairment/dementia was detected. The assessment of all variables is described in the supplementary material.