Table 2.
Demographic and clinical characteristics and outcome variables for the total sample and three subgroups, and differences in demographic and clinical characteristics and outcome variables among three subgroups
| All sample (n = 597) Mean ± SD n (%) |
Subgroup 1 All low (n = 192, 32·2%) Mean ± SD n (%) |
Subgroup 2 Moderate (n = 191, 32·0%) Mean ± SD n (%) |
Subgroup 3 All high (n = 214, 35·8%) Mean ± SD n (%) |
Test and statistical significance | |
|---|---|---|---|---|---|
| Age (years) | 65·93 ± 10·21 | 67·65 ± 5·95 | 66·41 ± 8·17 | 63·95 ± 13·90 |
F2,594 = 7·12, p = 0.001; all post hoc contrasts were significant, ;except between subgroups 1 and 2 |
| Male | 379 (63·5) | 132 (68·8) | 123 (64·4) | 124 (57·9) | χ2 = 5·20, p = 0.07 |
| White | 562 (94·1) | 180 (93·8) | 181 (94·8) | 201 (93·9) | χ2=0.21, p = 0.90 |
| Married | 385 (64·5) | 121 (63·0) | 129 (67·5) | 135 (63·1) | χ2 = 1·14, p = 0.57 |
| College degree or higher | 304 (50·9) | 114 (59·4) | 94 (49·2) | 96 (44·9) | χ2 = 8·86, p = 0.01; subgroup 1 > 2, p = 0.03; subgroup 1 > 3, p = 0.002 |
| Income ($30,000 or more) | 283 (47·5) | 98 (51·0) | 91 (47·6) | 94 (44·1) | χ2 = 1·94, p = 0.38 |
| Cigarette smoking, pack years | 67·44 ± 33·05 | 65·10 ± 33·30 | 63·73 ± 28·02 | 70·03 ± 36·59 | F2,591 = 2·06, p = 0.13 |
| Oxygen use at rest | 307 (51·4) | 80 (41·7) | 99 (51·8) | 128 (59·8) | χ2 = 13·4, p = 0.001; subgroup 1 < 2, p = 0.029; subgroup 1 < 3, p = 0.0001 |
| Oxygen use during sleeping | 392 (65·7) | 108 (56·2) | 127 (66·5) | 157 (73·4) | χ2 = 13·23, p = 0.001; subgroup 1 < 2, p = 0.025; subgroup 1 < 3, p = 0.0001 |
| FEV1 (% predicted) | 27·07 ± 7·10 | 28·41 ± 6·57 | 25·63 ± 7·13 | 27·15 ± 7·31 |
F2,594 = 7·51, p = 0.001; post hoc contrast between subgroups 1 and 2 was significant |
| FVC (% predicted) | 67·49 ± 15·78 | 70·69 ± 14·99 | 64·01 ± 15·94 | 67·71 ± 15·76 |
F2,594 = 8·84, p = 0.0001; post hoc contrast between subgroups 1 and 2 was significant |
| FEV1/FVC | 0.32 ± 0.06 | 0.32 ± 0.06 | 0.31 ± 0.06 | 0.32 ± 0.06 | F2,594 = 0.01, p = 0.99 |
| DLCO (% predicted) | 28·47 ± 9·82 | 30·31 ± 9·24 | 27·09 ± 9·69 | 28·03 ± 10·23 |
F2,590 = 5·54, p = 0.004; post hoc contrast between subgroups 1 and 2 was significant |
| PaO2 | 64·60 ± 10·17 | 65·56 ± 9·23 | 64·12 ± 11·03 | 64·17 ± 10·17 | F2,594 = 1·27, p = 0.28 |
| PaCO2 | 42·54 ± 5·27 | 41·54 ± 4·62 | 43·20 ± 5·38 | 42·86 ± 5·60 |
F2,594 = 5·47, p = 0.004; post hoc contrasts were significant, except between subgroups 2 and 3 |
| Maximum load in ergometer (watt) | 36·00 ± 20·87 | 43·41 ± 21·38 | 31·99 ± 19·60 | 32·87 ± 19·77 |
F2,581 = 18·80, p = 0.0001; all post hoc contrasts were significant, except between subgroups 2 and 3 |
| Mental component Scale in MOS-36 | 52·21 ± 10·88 | 59·99 ± 43·70 | 54·01 ± 8·13 | 43·70 ± 10·01 |
F2,590 = 192·08, p = 0.001; all post hoc contrasts were significant |
| Physical component scale in MOS-36 | 28·17 ± 7·16 | 32·22 ± 7·21 | 25·90 ± 6·28 | 26·59 ± 6·31 |
F2,590 = 53·04, p = 0.0001; all post hoc contrasts were significant, except between subgroups 2 and 3 |
| Number of nights staying in a hospital (n = 550) |
1·87 ± 4·77 | 1·71 ± 4·27 | 1·44 ± 4·62 | 2·43 ± 5·30 | F2,547 = 2·19, p = 0.11 |
| Number of nights staying in a rehab hospital or other nonacute care facility (n = 550) |
0.32 ± 3·28 | 0.19 ± 2·25 | 0.35 ± 4·13 | 0.42 ± 3·21 | F2,547 = 2·25, p = 0.78 |
| Number of visits to ER, triage or urgent care facility (n = 550) |
0.36 ± 0.73 | 0.34 ± 0.63 | 0.32 ± 0.74 | 0.40 ± 0.81 | F2,547 = 0.62, p = 0.54 |
| Number of visit to outpatient clinics or physician’s assistant or nurses (n = 550) |
3·83 ± 3·10 | 3·51 ± 2·69 | 3·73 ± 3·10 | 4·22 ± 3·42 | F2,547 = 0.25, p = 0.78 |
| Dead at five year follow up | 284 (47·6) | 74 (38·5) | 93 (48·7) | 117 (54·7) | χ2 = 10·70, p = 0.005; subgroup 1 < 2, p = 0.05; subgroup 1 < 3, p = 0.001 |
FEV1, forced expiratory volume in one second; FVC, forced vital capacity; DLCO, diffusion capacity of carbon monoxide; PaO2, partial pressure of oxygen in arterial blood; PaCO2, partial pressure of carbon dioxide in arterial blood; MOS-36, Medical Outcomes Study 36-Item Short-Form Health Survey.
The p-value presented for each pairwise post hoc contrast has been adjusted so that a value of < 0·05 indicates significance.