Table 1.
Characteristics of the Patients With AD, Young Controls, and Older Controls, Divided Into Past Cognitive Activity Tertilesa
| Characteristic | AD Patients | Young Controls | Older Controls
|
|||
|---|---|---|---|---|---|---|
| All | Bottom Tertile | Middle Tertile | Top Tertile | |||
| No. of study participants | 10 | 11 | 65 | 22 | 22 | 21 |
| Female, No. (%) | 3 (30) | 6 (55) | 42 (65) | 15 (68) | 12 (55) | 15 (71) |
| ApoE4 carriers, No. (%)b | 6/9 (67) | 5/8 (63) | 19/64 (30) | 8/21 (38) | 4/22 (18) | 7/21 (33) |
| ApoE4 allele frequency, % | 0.44 | 0.31 | 0.16 | 0.23 | 0.09 | 0.17 |
| [11C]PiB uptakec | 1.54 (0.24) | 1.04 (0.24) | 1.11 (0.16) | 1.22 (0.23) | 1.08 (0.08) | 1.03 (0.06) |
| Age, y | 74.8 (8.7) | 24.5 (3.7) | 76.1 (6.3) | 76.3 (5.6) | 76.0 (6.4) | 76.2 (7.0) |
| Years of education | 17.1 (2.8) | 16.2 (1.9) | 17.0 (2.1) | 16.7 (2.3) | 17.0 (2.2) | 17.3 (1.8) |
| MMSE scored | 19.5 (8.0) | … | 29.0 (1.3) | 28.7 (1.5) | 28.9 (1.4) | 29.3 (0.7) |
| Depression score (maximum, 30)e | … | 3.3 (2.7) | 3.6 (2.8) | 3.1 (2.3) | 3.2 (3.0) | |
| Memory score (maximum, 80)f | … | 55.4 (8.2) | 47.5 (10.2) | 45.1 (11.7) | 47.8 (9.5) | 49.9 (9.0) |
| Physical activity interview, kcalg | … | … | 4965 (3792) | 3507 (3059) | 4325 (2127) | 7163 (4856) |
| Cognitive activity interview scoreh | ||||||
| Past (maximum, 5) | … | … | 3.50 (0.63) | 2.80 (0.43) | 3.55 (0.17) | 4.17 (0.20) |
| Current (maximum, 5) | … | … | 3.93 (0.59) | 3.51 (0.48) | 3.98 (0.60) | 4.30 (0.39) |
| Lifetime (maximum, 5) | … | … | 3.55 (0.58) | 2.93 (0.39) | 3.60 (0.23) | 4.16 (0.20) |
Abbreviations: AD, Alzheimer disease; ApoE4, apolipoprotein E4; MMSE, Mini-Mental State Examination; [11C]PiB, carbon 11–labeled Pittsburgh B Compound.
Data are presented as mean (SD) unless otherwise indicated.
ApoE4 carriers are the percentage of individuals who have at least 1 ApoE ε4 allele. ApoE4 carrier status was determined for 64 of 65 healthy older participants, 8 of 11 young participants, and 9 of 10 patients with AD.
[11C]PiB uptake was lower in young controls than older controls (P = .04) and higher in patients with AD than older or younger controls (P <.001). Within older controls, the tertiles differed from one another (P = .001) such that the lowest tertile had higher [11C]PiB uptake than both the middle tertile (P = .04) and the top tertile (P = .001), and the middle and highest tertiles were marginally different (P = .06).
The MMSE score was lower for patients with AD compared with older controls (P <.001).
The depression score is the score on the Geriatric Depression Scale.
The memory score is performance on the free recall portion (sum of trials 1–5) of the California Verbal Learning Test.
Tertiles differed with respect to current physical activity level (P = .004) such that the highest cognitive activity tertile had greater energy expenditure than the middle tertile (P = .02) and lowest tertile (P = .003). The current physical activity interview scores were calculated by multiplying the time reported for each physical or leisure activity (eg, walking, cycling, dancing, or yoga) during a recent 2-week period by an intensity index for that activity.
Items in the cognitive activity interview were scored according to a frequency scale: 5, every day or almost every day; 4, several times a week; 3, several times a month; 2, several times a year; and 1, once a year or less. The total cognitive activity score (average across all age epochs) was subdivided into a past cognitive activity score (average across epoch means for ages 6, 12, 18, and 40 years) and a current cognitive activity score (average of current epoch only).