Demographic data
Altogether 52 individuals (31 male: 59,62%, 21 females: 40,38%) with Alzheimer’s disease diagnosis participated in the study. The participant’s mean age was 72,62 ± 7,57 years. Their mean duration of education was 13,00 ± 2,56 years. All patients showed the typical characteristic of cortical atrophy (bifrontal-bitemporal atrophy with reduced hippocampi). All patients had medial temporal lobe atrophy score ≥ 3.
Group 1 (n = 15; disease duration of no more than 2 years) included 11 male (73,33%) and 4 female (26,67%) participants with a mean age of 70,07 ± 9,5 years. In group 2 (n = 26; disease duration of 2 to 4 years) there were 15 male (57,69%) and 11 female (42,31%) participants. Their mean age was 73,46 ± 6,85 years. In group 3 (n = 11; disease duration longer than 4 years) 5 male (45,45%) and 6 female (54,55%) participants were selected, with a mean age of 74,09 ± 5,72 years. We studied between-group differences in sex, age, age at disease onset, education level, disease duration, ACE total score and VLOM ratio (Table 1). Kruskal-Wallis test showed significant differences in disease duration, ACE total score and MMSE score between the three groups (all p values < 0,001).
Table 1
Demographic and clinical data of participants.
Parameter
|
Total
|
Group 1
|
Group 2
|
Group 3
|
p-value
|
Participants (n)
|
52
|
15
|
26
|
11
|
-
|
Male, n (%)
|
31 (59,6%)
|
11 (73,3%)
|
15 (57,7%)
|
5 (45,5%)
|
0,17
|
Female, n (%)
|
21 (40,4%)
|
4 (26,7%)
|
11 (42,3%)
|
6 (54,5%)
|
0.053
|
Age (years) median ratio (IQ1-IQ3)
|
73,0(69,3–77,0)
|
71,0 (63,0–77,0)
|
73,5 (71,0–76,5)
|
73,0 (70,0–79,0)
|
0,40
|
Age at disease onset (years) mean ± SD
|
69,8 ± 7,4
|
68,7 ± 9,4
|
70,5 ± 6,9
|
69,6 ± 5,9
|
0,78
|
Education (years)
|
12,0(12,0–17,0)
|
12,0(12,0–17,0)
|
12,0(12,0–17,0)
|
12,0(10,0–12,0)
|
0,25
|
Disease duration (years) median ratio (IQ1-IQ3)
|
3,0(2,0–3,0)
|
1,0(0,0–2,0)
|
3,0(2,0–4,0)
|
4,0(4,0–5,0)
|
< 0,001
|
ACE total score median ratio (IQ1-IQ3)
|
67,0(55,3–75,0)
|
72,0(67,0–79,0)
|
67,5(55,0–76,3)
|
50,0(44,0–59,0)
|
< 0,001
|
VLOM median ratio (IQ1-IQ3)
|
3,4(3,2–4,1)
|
3,4(3,2–3,9)
|
3,5(3,2–4,3)
|
3,4(3,3–3,6)
|
0,995
|
MMSE median (IQ1-IQ3)
|
20,0(16,0–23,0)
|
25,0(22,0–25,0)
|
19,5(16,0–21,3)
|
15,0(12,0–18,0)
|
< 0,001
|
Orientation
median ratio (IQ1-IQ3)
|
7,0(6,0–8,0)
|
9,0(7,0–10,0)
|
7,0(6,0–8,0)
|
7,0(5,0–8,0)
|
0,015
|
Attention
median ratio (IQ1-IQ3)
|
6,0(4,3–7,0)
|
6,0(5,0–7,0)
|
6,5(5,0–7,0)
|
4,0(4,0–7,0)
|
0,097
|
Memorymean ± SD
|
20,0 ± 5,0
|
22,2 ± 3,5
|
21,0 ± 4,9
|
14,6 ± 3,2
|
< 0,001
|
Verbal fluency mean ± SD
|
8,5 ± 2,5
|
9,1 ± 1,9
|
8,6 ± 2,4
|
7,5 ± 3,4
|
0,27
|
Language mean ± SD
|
20,4 ± 4,6
|
22,9 ± 2,5
|
20,3 ± 5,0
|
17,3 ± 4,0
|
0,006
|
Visuospatial abilities median ratio (IQ1-IQ3)
|
3,0(2,0–4,0)
|
4,0(4,0–5,0)
|
2,5(2,0–3,0)
|
1,0(1,0–2,0)
|
< 0,001
|
Statistical tests applied were Chi-square for sex, ANOVA for parametric and Kruskal-Wallis for non-parametric statistics. Significant differences are present in disease duration, ACE total score and MMSE score between the three groups (all p values < 0,001). One-way ANOVA analysis was used for between-group differences in memory, language and verbal fluency. Kruskal-Wallis test was used for between-group differences in orientation, attention and visuospatial abilities.SD: standard deviation; MMSE: Mini-Mental State Examination IQ1-IQ3: interquartile range
Relationship between ACE total score and disease duration
Spearman’s rho showed a significant negative correlation between ACE total scores and disease duration (p < 0,001; r:-0,544). To support this finding a one-way ANOVA was used confirming significant group effect on total ACE score (F = 12,14; p < 0,001).
Between-group differences between ACE subscores
One-way ANOVA was used to test within-group differences between subscores of memory, language and verbal fluency data (Table 1). Significant between-group differences were found for memory (F = 12,05; p < 0,001) and language (F = 5,62; p = 0,006). Kruskal-Wallis test was applied to study between-group differences between subscores of orientation, attention and visuospatial abilities (Table 1). Significant between-group differences were found for visuospatial abilities (χ2 = 28,36; p < 0,001) and orientation (χ2 = 8,42; p = 0,015). Age, sex, disease onset and disease duration did not have significant modifier effect on between group differences (all p values > 0.05). Post-hoc analysis revealed that Group 1 differs from Group 2 and Group 3 in orientation skills (all p values < 0.05) but Group 2 and Group3 are not significantly different (p:0.899). As for memory, difference between Group 1 and Group 2 was not significant (p:0.63), while Group 2 and Group 3 showed significant differences (p < 0.001). Regarding language, only Group 3 and Group 1 differed (p: 0.004). In visuospatial skills all groups differed significantly (all p values < 0.05) (Fig. 1).
Relationship between ACE subscores and disease duration
Spearman’s rho was applied to test the relationship between all six ACE subscores and disease duration (Table 2). Significant negative correlation was found between disease duration and orientation (p = 0,01; r:-0,35) memory (p < 0,001; r:-0,52), language (p < 0,001; r:-0,48) and visuospatial abilities (p < 0,001; r:-0,73) (Fig. 2).
Table 2
Correlation analysis between ACE subscores and disease duration using Spearman’s rho.
|
Orientation
|
Attention
|
Memory
|
Verbal fluency
|
Language
|
Visuospatial abilities
|
p
|
0,01
|
0,09
|
< 0,001
|
0,047
|
< 0,001
|
< 0,001
|
r
|
-0,35
|
-0,24
|
-0,52
|
-0,28
|
-0,48
|
-0,73
|
Within-group differences between ACE subscores
We applied the Friedman test for within-group difference analysis between ACE subscores. Differences between the normalized subscores are shown in Fig. 3. We found significant differences (all p’s < 0.001) between the subscores in all groups (Table 3). Tukey test was applied for posthoc analysis.
In Group 1, normalized subscore of orientation was significantly higher than memory (p = 0.003) and verbal fluency (p = 0.002). Normalized subscore of attention was significantly higher than memory (p = 0.017) and verbal fluency (p = 0.01). Normalized subscore for memory was significantly reduced compared to language (p = 0.003) and visuospatial skills (p = 0.004); verbal fluency was significantly lower than language (p = 0.002) and visuospatial abilities (p = 0.003).
In Group 2, normalized subscore of orientation was significantly higher than memory (p = 0,006), verbal fluency (p:0,039) and visuospatial abilities (p:0,001); and significantly lower than attention (p:0,034). Normalized subscore of attention was significantly higher than memory (p < 0,001), verbal fluency (p < 0,001) and visuospatial abilities (p < 0,001). Normalized subscore of memory was significantly higher than visuospatial abilities (p:0,011) and significantly reduced compared to language (p:0,003). Normalized subscore of verbal fluency was significantly higher than visuospatial abilities (p:0,09) and significantly lower than language (p:0,05). Normalized subscore of language was significantly higher than visuospatial abilities (p:0,001).
In Group 3, normalized subscore of orientation was significantly higher than memory (0,003) and visuospatial abilities (p:0,005). Normalized subscore of attention was significantly higher than memory (p:0,006) and visuospatial abilities (p = 0,005). Normalized subscore of memory was significantly reduced compared to language (p = 0,003). Normalized subscore of verbal fluency was significantly higher than visuospatial abilities (p:0,008). Normalized subscore of language was significantly higher than visuospatial abilities (p:0,008).
Table 3
Normalized ACE subscores for orientation, attention, memory, verbal fluency, language and visuospatial abilities per group.
|
|
Group 1
|
Group 2
|
Group 3
|
Orientation
|
Mean
|
0,85
|
0,69
|
0,66
|
SD
|
0,18
|
0,15
|
0,14
|
Attention
|
Mean
|
0,76
|
0,76
|
0,61
|
SD
|
0,17
|
0,20
|
0,19
|
Memory
|
Mean
|
0,63
|
0,60
|
0,42
|
SD
|
0,10
|
0,14
|
0,09
|
Verbal fluency
|
Mean
|
0,65
|
0,61
|
0,53
|
SD
|
0,14
|
0,17
|
0,24
|
Language
|
Mean
|
0,82
|
0,73
|
0,62
|
SD
|
0,10
|
0,18
|
0,14
|
Visuospatial abilities
|
Mean
|
0,81
|
0,49
|
0,26
|
SD
|
0,14
|
0,21
|
0,20
|