Table 2.
Adjusted Changes in Global Cognitive Function over Time among All Participants: REGARDS Study, 2003 to 2013
| Six-Item Screener Score (n=23,572) | Incident Cognitive Impairment Six-Item Screener <5 (n=23,572) | |||||||
|---|---|---|---|---|---|---|---|---|
| No. of incident strokes | 515 | 515 | ||||||
| Model | Model A | Model B | Model A | Model B | ||||
| Variable | Coefficient (95% CI) | P | Coefficient (95% CI) | P | Odds Ratio (95% CI) | P | Odds Ratio (95% CI) | P |
| Baseline cognitive score per 1 point increase | 0.18 (0.16 – 0.19) | <0.001 | 0.18 (0.16 –0.19) | <0.001 | 0.53 (0.49 – 0.57) | <0.001 | 0.53 (0.49 –0.57) | <0.001 |
| Baseline slope without incident stroke, per year | 0.02 (0.02 – 0.02) | <0.001 | 0.02 (0.02 –0.02) | <0.001 | 0.88 (0.86 – 0.90) | <0.001 | 0.88 (0.85 –0.90) | <0.001 |
| Acute change after incident stroke compared to before stroke | −0.21 (−0.25 – −0.16) | <0.001 | −0.10 (−0.17 –−0.04) | 0.001 | 1.98 (1.58 – 2.48) | <0.001 | 1.32 (0.95 –1.83) | 0.097 |
| Change in slope after incident stroke, per year | Not included | −0.06 (−0.08 – −0.03) | <0.001 | Not included | 1.23 (1.10 – 1.38) | <0.001 | ||
| Age, per year | −0.02 (−0.02 – −0.01) | <0.001 | −0.02 (−0.02 –−0.01) | <0.001 | 1.07 (1.07 – 1.08) | <0.001 | 1.07 (1.07 – 1.08) | <0.001 |
| Intercept | 5.3 (5.16 – 5.41) | <0.001 | 5.28 (5.15 to 5.40) | <0.001 | NA | NA | ||
| Log likelihood | −113758.2 | −113747.1 | −25151.4 | −25146.2 | ||||
Interpretative Key: The Six-Item Screener (SIS) measures global cognition (scores range 0–6). Higher scores indicate better performance. The SIS was analyzed as a continuous measure and as a binary measure of incident cognitive impairment (SIS<5/impaired vs. ≥5/unimpaired).
Linear mixed-effects models included a random intercept, calendar time, and adjust for time-varying incident stroke, time since incident stroke, and baseline values of cognitive scores, age, sex, race, education, region, systolic blood pressure, cigarette smoking, waist circumference, diabetes, self-reported stroke, depressive symptoms, income, alcohol use, self-reported health status, and a random effect for slope. Generalized linear mixed-effects models for a binary outcome were used for estimating the odds of incident cognitive impairment.
Interpretative example for the SIS score as a continuous measure: An average participant had been gaining 0.02 points per year on the SIS of global cognition (95% confidence interval, 0.02–0.02; P<0.001) before having a stroke. An average stroke survivor’s SIS score decreased 0.10 points at the time of the stroke (95% confidence interval, 0.04–0.17; P=0.001). Over the years following stroke, survivors experienced a significant annual decrease in SIS scores. The average stroke survivor’s SIS score decreased 0.06 points per year compared to the baseline (prestroke) slope (95% confidence interval, 0.03–0.08; P<0.001).
Interpretative example for incident cognitive impairment as a binary measure (SIS<5/impaired vs. ≥5/unimpaired): The odds ratio is the odds of developing cognitive impairment compared to the odds of not developing cognitive impairment. Before stroke, participants experienced a significant annual decrease in the odds of developing cognitive impairment. The odds of participants developing cognitive impairment in a given prestroke year were 0.88 times lower than the odds of developing cognitive impairment during the previous year (odds ratio, 0.88 per year; 95% CI, 0.85–0.90; P<0.001). The risk of cognitive impairment acutely after stroke was not significantly different than the risk of cognitive impairment before stroke. The odds of developing cognitive impairment acutely after stroke were a non-significant 1.32 times greater than the odds of developing cognitive impairment immediately before stroke (odds ratio, 1.32; 95% CI, 0.95–1.83; P=0.097). However, stroke survivors experienced a significant annual increase in odds of developing cognitive impairment representing a significantly faster rate of incident cognitive impairment after stroke compared to the prestroke rate (odds ratio, 1.23 per year; 95% CI, 1.10–1.38; P<0.001), controlling for the odds of developing cognitive impairment before or acutely after the event. The odds of survivors developing cognitive impairment in a given poststroke year were 1.23 times greater than the odds of developing cognitive impairment during the previous year.