The analytic sample of 767 persons completed 4410.6 person-years of follow-up with 116 (15.1%) cases of possible or probable AD. reports descriptive and demographic statistics by final AD status. Subjects who subsequently developed AD (compared to those who did not) were older (t=7.3, p < 0.001) and were more likely to have less than 12 years or 16 or more years of schooling (chi-square = 11.5, d f = 3, p < 0.001), but did not differ statistically by gender or race. Rates of disease at study entry were as follows: hypertension (54.1%), diabetes (8.0%), osteoporosis (12.0%) cancer within the past five years (21.8%), and cardio-vascular disease (25.8%); 51.3% self-rated their health as excellent or very good (vs. good, fair or poor). reports the descriptive statistics for the personality traits and key covariates along with the intercorrelations among variables. Those with a final diagnosis of AD compared to those without had lower initial 3MSE (mean [SD] 91.2 [4.9] vs. SD94.7 [4.1], t = 8.3, p < 0.001) and had more depressive symptoms (mean [SD] 4.9 [4.4] vs. 3.6 [3.4], t = 3.5, p < 0.001).
Baseline Demographic Characteristics Of Participants, By Final Dementia Status
Descriptive Statistics And Intercorrelations Among Key Variables (N=767)
reports the adjusted hazard ratios (AHR) and 95% confidence intervals (CI) for possible and probable AD for each of the personality traits. Each trait is reported in two rows. The top row shows the AHR for that trait when no other personality trait is entered in the model. The bottom row shows the AHR for that trait when the other four traits are entered in the model. Of the four base model covariates (age, gender, education, and race), only age was independently associated with AD risk. Older participants [AHR (95% CI) = 1.20 (1.14, 1.26)] were at greater risk of developing AD over the follow-up period.
Adjusted Hazard Ratios (AHR) For Probable Or Possible Alzheimer’s Disease (N=767)
Analyses of the base model revealed that, over and above the effects of age, gender, race, and education, AD risk was greater among participants higher in Neuroticism and lower in Openness and Conscientiousness. Whereas the substantive findings for Neuroticism and Openness were unaffected by the addition of other personality traits to the model, the effect of Conscientiousness on AD risk was no longer statistically significant in the presence of other traits. The AHR (95 % CI) changed from 0.76 (0.63, 0.93) to 0.86 (0.69, 1.08).
In a model that added the 3MSE score at study entry to the base model, participants higher in Neuroticism and lower in Openness and Conscientiousness remained at greater risk. The AHRs for Neuroticism and Conscientiousness were slightly larger than corresponding figures for the base model. Whereas the substantive finding for Neuroticism was unaffected by the addition of other personality traits to the model, the effects of Openness and Conscientiousness were no longer statistically significant in the presence of other traits. People who scored lower on the 3MSE at study entry were more likely to develop AD, AHR (95%CI) = 0.84 (0.81, 0.88).
In a model that added the CES-D-10 score at study entry to the base model, higher Neuroticism and lower Openness and Conscientiousness were still associated with AD risk. The AHRs for Neuroticism and Conscientiousness were slightly smaller than the base model AHRs. Whereas the substantive finding for Openness was unaffected by the addition of other personality traits to this model, the effects of Neuroticism and Conscientiousness were no longer significant in the presence of other traits. There was a positive association between CES-D-10 scores and AD risk, though it was not as large as the effect of 3MSE [AHR (95%CI) =1.08 (1.02, 1.13)].
Adding the five morbidity indicators did not substantially alter the overall pattern of findings from the base model, but the AHRs for Neuroticism and Openness were slightly attenuated. For example, the AHR (95% CI) for the former decreased from 1.39 (1.16, 1.67) to 1.35(1.11, 1.64). Corresponding figures for the latter decreased from 0.78 (0.64, 0.95) to 0.76 (0.62, 0.93). Cardiovascular disease [AHR (95% CI) = 1.77 (1.18, 2.65)] and osteoporosis [AHR (95% CI) = 1.09 (1.00, 1.18)] were both associated with increased AD risk, but diabetes, cancer over the past 5 years, and hypertension were not.
In a model that added the disease indicators, CES-D-10, and 3MSE to the base model covariates (data not shown), the overall pattern was retained. AD risk was tied to higher Neuroticism [AHR (95% CI) =1.36 (1.08,1.71)] and lower Openness [AHR (95% CI) =.80 (0.65, 0.98)] and Conscientiousness [AHR (95% CI)=.71 (0.57, 0.89)].
To provide a graphic illustration of the findings, three personality profiles were constructed. presents the Kaplan-Meier probability of developing AD over the study duration for those with differing personality profiles.
Figure 1 Kaplan-Meier probability of developing AD over the study duration. High risk: Scored above mean on Neuroticism and below mean on Openness and Conscientiousness. Low risk: Scored below mean on Neuroticism and above mean on Openness and Conscientiousness. (more ...)
Relative to the low risk group, the AD HR for high risk group was 2.64 (95% CI = 1.46, 4.77) and was 1.41 (95% CI = 0.83, 2.40) for the average risk group; with full adjustment (age, gender, education, CES-D, 3MSE, morbidity indicators) the respective HRs were 2.11 (95% CI = 1.07, 4.16) and 1.29 (95% CI = 0.74, 2.27).
Finally, the supplementary and sensitivity analyses revealed no significant interactions between the personality variables and any of the other covariates. There were no gender differences in the relationships between personality and AD risk. None of the squared trait terms were significant.