The plasma p-tau concentration was measured by the single-molecule immunoarray (Simoa) method with reagents from a single lot using the Simoa P-tau181 assay on an HD-1 Simoa analyzer according to the protocol issued by the manufacturer (Quanterix, Lexington, MA, USA). All samples were analyzed in duplicate on one occasion.
Apolipoprotein E (ApoE) haplotype were determined with genotyping by Invader assay or DNA microarray method undertaken by BML Inc (Tokyo, Japan) or PreMedica inc. (Tokyo, Japan) or phenotyping by isoelectricelectrophoresis for plasma 27 undertaken by BML Inc (Tokyo, Japan).
Statistics
A comparison between the two independent groups was performed using Mann-Whitney’s U test. The Chi-square test was used to evaluate the significance of categorical variables. Univariate correlation analysis was conducted using Spearman’s rank correlation coefficient test (Spearman’s test). Difference of slopes of regression lines was determined by significance of interaction term in the analysis of covariance (ANCOVA). (SPSS ver. 23, IBM Japan Ltd, Tokyo, Japan) Multiple regression analysis was performed with plasma phosphorylated tau concentration after log-transformed as the dependent variable and DSQIID sub-items and age as explanatory variables. SPSS ver. 23 (IBM Japan Ltd, Tokyo, Japan), was used for multivariate analyses. The normality test for residuals of multiple regression analysis was performed by the D'Agostino-Pearson omnibus normality test and Shapiro-Wilk normality test. The above analyses were carried out using GraphPad Prism software version 9.0 (San Diego, CA, USA). The level of significance was set at P < 0.05.
Table 1
Demographics of the participants
Participants with blood collection | DS group | Control group | P value |
Number of cases | 56 | 33 | |
Age (mean ± SD) | 31.66 ± 10.89 | 34.82 ± 10.82 | P = 0.1291 |
Sex | Female:27, Male:29 | Female:14, Male:19 | P = 0.6630 |
plasma p-tau (pg/ml) (mean ± SD) | 2.06 ± 2.11 | 0.72 ± 0.40 | P < 0.0001 |
ApoE type | | | |
E2/2 | 0 | N/A | |
E2/3 | 3 | N/A | |
E3/3 | 40 | N/A | |
E3/4 | 11 | N/A | |
E4/4 | 0 | N/A | |
N/A | 2 | N/A | |
Participants with DSQIID examined within 2 years of blood collection | DS group | | |
Number of cases | 43 | | |
Age (mean ± SD) | 32.21 ± 10.79 | | |
Sex | Female:21, Male:22 | | |
plasma p-tau (pg/ml) (mean ± SD) | 2.022 ± 2.20 | | |
DSQIID total score (median (minimum-maximum) | 9 (0–38) | | |
E2/2 | 0 | | |
E2/3 | 1 | | |
E3/3 | 31 | | |
E3/4 | 9 | | |
E4/4 | 0 | | |
N/A | 2 | | |
SD: standard deviation, NA: not available, |
Table 2
Correlation between sub-items of DSQIID, age, and plasma p-tau levels
Sub-items of DSQIID | Univariate analysis for age | Univariate analysis for p-tau | Multivariate analysis for log p-tau value |
each score | age |
rs | P-value | rs | P-value | β | P-value | β | P-value |
Part 2 | | | | | | | | |
1. Cannot wash and/or bathe without help | 0.053 | 0.735 | 0.269 | 0.081 | 0.120 | 0.215 | 0.778 | < 0.001 |
2. Cannot dress without help | 0.256 | 0.098 | 0.323 | 0.035 | 0.017 | 0.866 | 0.788 | < 0.001 |
3. Dresses inappropriately (e.g. back to front, incomplete) | 0.374 | 0.014 | 0.352 | 0.021 | -0.034 | 0.750 | 0.807 | < 0.001 |
4. Undresses inappropriately (e.g. in public) | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
5. Needs help eating | 0.303 | 0.048 | 0.319 | 0.037 | 0.120 | 0.249 | 0.747 | < 0.001 |
6. Needs help using the bathroom | 0.23 | 0.138 | 0.223 | 0.15 | -0.046 | 0.642 | 0.805 | < 0.001 |
7. Incontinent (including occasional accidents) | 0.103 | 0.51 | 0.09 | 0.565 | -0.059 | 0.541 | 0.798 | < 0.001 |
8. Does not initiate conversation | 0.150 | 0.336 | 0.272 | 0.078 | -0.013 | 0.898 | 0.796 | < 0.001 |
9. Cannot find words | 0.166 | 0.293 | 0.398 | 0.009 | 0.049 | 0.623 | 0.783 | < 0.001 |
10. Cannot follow simple instructions | 0.280 | 0.069 | 0.351 | 0.021 | 0.131 | 0.196 | 0.751 | < 0.001 |
11. Cannot follow more than one instruction at a time | 0.401 | 0.008 | 0.482 | 0.001 | -0.034 | 0.756 | 0.809 | < 0.001 |
12. Stops in the middle of a task | 0.142 | 0.364 | 0.266 | 0.084 | 0.036 | 0.713 | 0.788 | < 0.001 |
13. Cannot read | 0.191 | 0.221 | 0.299 | 0.052 | 0.048 | 0.632 | 0.780 | < 0.001 |
14. Cannot write (including printing own name) | 0.17 | 0.275 | 0.315 | 0.04 | 0.115 | 0.243 | 0.769 | < 0.001 |
15. Changed sleep pattern (sleeping more or sleeping less) | -0.077 | 0.622 | -0.013 | 0.936 | 0.100 | 0.298 | 0.799 | < 0.001 |
16. Wakes frequently at night | 0.224 | 0.148 | 0.222 | 0.153 | -0.032 | 0.751 | 0.802 | < 0.001 |
17. Confused at night | -0.181 | 0.247 | -0.184 | 0.238 | -0.028 | 0.777 | 0.789 | < 0.001 |
18. Sleeps during the day | 0.035 | 0.823 | -0.076 | 0.628 | -0.109 | 0.258 | 0.799 | < 0.001 |
19. Wanders at night | -0.112 | 0.474 | -0.236 | 0.127 | -0.073 | 0.454 | 0.786 | < 0.001 |
20. Cannot find way in familiar surroundings | 0.213 | 0.17 | 0.161 | 0.302 | -0.031 | 0.753 | 0.799 | < 0.001 |
21. Wanders | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
22. Loses track of time (time of day, day of the week, seasons) | 0.068 | 0.666 | 0.211 | 0.175 | 0.091 | 0.345 | 0.786 | < 0.001 |
23. Not confident walking over small cracks, lines on the ground or uneven surfaces | 0.368 | 0.015 | 0.27 | 0.08 | -0.026 | 0.802 | 0.804 | < 0.001 |
24. Unsteady walk, loses balance | 0.214 | 0.169 | 0.251 | 0.104 | 0.106 | 0.290 | 0.765 | < 0.001 |
25. Cannot walk unaided | 0.321 | 0.036 | 0.302 | 0.049 | 0.008 | 0.940 | 0.791 | < 0.001 |
26. Cannot recognize familiar person (staff / relatives) | -0.237 | 0.127 | -0.187 | 0.231 | 0.032 | 0.749 | 0.800 | < 0.001 |
27. Cannot remember names of familiar persons | 0.000 | > 0.999 | 0.228 | 0.141 | 0.145 | 0.128 | 0.784 | < 0.001 |
28. Cannot remember recent events | 0.28 | 0.069 | 0.31 | 0.043 | 0.035 | 0.729 | 0.783 | < 0.001 |
29. Withdraws from social activities | -0.04 | 0.8 | 0.071 | 0.651 | -0.025 | 0.797 | 0.794 | < 0.001 |
30. Withdraws from other persons | 0.000 | > 0.9999 | 0.231 | 0.137 | 0.060 | 0.537 | 0.792 | < 0.001 |
31. Loss of interest in hobbies and activities | 0.098 | 0.533 | 0.217 | 0.162 | -0.043 | 0.659 | 0.796 | < 0.001 |
32. Seems to go into own world | 0.076 | 0.628 | 0.115 | 0.462 | -0.025 | 0.796 | 0.794 | < 0.001 |
33. Obsessive repetitive behaviour (e.g. empties cupboards repeatedly) | -0.043 | 0.784 | 0.09 | 0.565 | -0.056 | 0.567 | 0.787 | < 0.001 |
34. Hides or hoards objects | 0.162 | 0.299 | 0.11 | 0.481 | -0.100 | 0.301 | 0.801 | < 0.001 |
35. Loses objects | 0.187 | 0.229 | 0.14 | 0.37 | -0.026 | 0.792 | 0.797 | < 0.001 |
36. Puts familiar things into wrong places | 0.413 | 0.006 | 0.424 | 0.005 | 0.040 | 0.703 | 0.779 | < 0.001 |
37. Does not know what to do with familiar objects | 0.423 | 0.005 | 0.444 | 0.003 | 0.186 | 0.080 | 0.711 | < 0.001 |
38. Appears insecure | 0.139 | 0.4 | 0.14 | 0.37 | -0.009 | 0.926 | 0.795 | < 0.001 |
39. Appears anxious or nervous | -0.141 | 0.368 | 0.06 | 0.703 | 0.052 | 0.594 | 0.800 | < 0.001 |
40. Appears depressed | 0.133 | 0.397 | 0.271 | 0.079 | 0.072 | 0.456 | 0.787 | < 0.001 |
41. Shows aggression (verbal or physical) | -0.06 | 0.702 | 0.04 | 0.799 | -0.013 | 0.897 | 0.793 | < 0.001 |
42. Fits / epilepsy | 0.151 | 0.334 | -0.059 | 0.708 | -0.043 | 0.655 | 0.798 | < 0.001 |
43. Talks to self | 0.188 | 0.227 | 0.159 | 0.309 | -0.175 | 0.068 | 0.821 | < 0.001 |
Part 3. | | | | | | | | |
44. Lost some skills (e.g. brushing teeth) | 0.178 | 0.253 | 0.212 | 0.172 | 0.032 | 0.745 | 0.788 | < 0.001 |
45. Speaks (or signs) less | -0.044 | 0.779 | 0.092 | 0.557 | -0.005 | 0.960 | 0.793 | < 0.001 |
46. Seems generally more tired | 0.017 | 0.912 | 0.1 | 0.525 | -0.013 | 0.891 | 0.795 | < 0.001 |
47. Appears tearful, gets more easily upset | 0.355 | 0.02 | 0.408 | 0.007 | 0.036 | 0.734 | 0.780 | < 0.001 |
48. Appears generally slower | 0.18 | 0.247 | 0.42 | 0.005 | 0.041 | 0.679 | 0.786 | < 0.001 |
49. Slower speech | 0.257 | 0.096 | 0.33 | 0.031 | -0.054 | 0.585 | 0.806 | < 0.001 |
50. Appears more lazy | 0.072 | 0.647 | 0.196 | 0.207 | -0.016 | 0.871 | 0.794 | < 0.001 |
51. Walks slower | 0.142 | 0.365 | 0.248 | 0.109 | 0.122 | 0.210 | 0.771 | < 0.001 |
52. Generally, appears more forgetful | 0.253 | 0.101 | 0.094 | 0.549 | -0.224 | 0.020 | 0.847 | < 0.001 |
53. Generally, appears more confused | 0.199 | 0.201 | 0.263 | 0.088 | -0.016 | 0.874 | 0.797 | < 0.001 |
DSQIID total score | 0.265 | 0.086 | 0.454 | 0.002 | 0.180 | 0.862 | 0.788 | < 0.001 |
N/A: Not Applicable because no subjects were scored for the relevant sub-items.
β: standardized partial regression coefficient
Significant correlations between the scores of sub-items and p-tau levels were highlighted in bold.
Note
Age-adjusted multivariate analysis was performed using multiple regression analysis. Significant models were obtained for all analyses. No model was significantly different in the D'Agostino-Pearson omnibus and Shapiro-Wilk normality tests of residuals.
Table 3
Correlation between scores of sub-components of DSQIID part 2, age, and plasma p-tau levels
Sub-components of DSQIID part 2 | Univariate analysis for age | Univariate analysis for p-tau | Multivariate analysis for log p-tau value |
each score | age |
rs | P-value | rs | P-value | β | P-value | β | P-value |
Component 1: Memory / confusion | 0.336 | 0.028 | 0.521 | 0.0003 | 0.085 | 0.417 | 0.762 | < 0.001 |
Component 2: Feelings of insecurity | 0.248 | 0.108 | 0.446 | 0.003 | 0.019 | 0.854 | 0.788 | < 0.001 |
Component 3: Sleep problems | 0.093 | 0.553 | 0.074 | 0.637 | -0.025 | 0.800 | 0.797 | < 0.001 |
Component 4: Behaviour problems | 0.155 | 0.322 | 0.282 | 0.067 | -0.041 | 0.674 | 0.798 | < 0.001 |
Scores on the 43 questions that comprise Part 2 of the DSQIID score were categorized into the four components shown below. The scores for each component are the unweighted sum of the scores on the questions of the component.
Component 1: 1. Cannot wash and/or bathe without help, 2. Cannot dress without help, 3. Dresses inappropriately (e.g. back to front, incomplete), 9. Cannot find words, 10. Cannot follow simple instructions, 11. Cannot follow more than one instruction at a time, 12. Stops in the middle of a task, 13. Cannot read, 14. Cannot write (including printing own name), 17. Confused at night, 20. Cannot find way in familiar surroundings, 22. Loses track of time (time of day, day of the week, seasons), 23. Not confident walking over small cracks, lines on the ground or uneven surfaces, 26. Cannot recognize familiar person (staff / relatives), 27. Cannot remember names of familiar persons, 28. Cannot remember recent events, 32. Seems to go into own world, 37. Does not know what to do with familiar objects, and 43. Talks to self.
Component 2: 2. Cannot dress without help, 5. Needs help eating, 6. Needs help using the bathroom, 7. Incontinent (including occasional accidents), 8. Does not initiate conversation, 24. Unsteady walk, loses balance, 25. Cannot walk unaided, 29. Withdraws from social activities, 30. Withdraws from other persons, 31. Loss of interest in hobbies and activities, 38. Appears insecure, 39. Appears anxious or nervous, and 40. Appears depressed.
Component 3: 4. Undresses inappropriately (e.g. in public), 15. Changed sleep pattern (sleeping more or sleeping less), 16. Wakes frequently at night, 18. Sleeps during the day, 19. Wanders at night, 21. Wanders, and 42. Fits / epilepsy.
Component 4: 33. Obsessive repetitive behaviour (e.g. empties cupboards repeatedly), 34. Hides or hoards objects, 35. Loses objects, 36. Puts familiar things into wrong places, and 41. Shows aggression (verbal or physical) 15