Table 1. Clinical characteristics of participants living below the poverty line (n=3,223).
| Variable | Living below poverty line (n=832) | Living above poverty line (n=2,391) | P |
|---|---|---|---|
| Age (years)* | 64±11 | 54±10 | <0.001 |
| Male, n (%) | 323 (38.8) | 1,090 (45.6) | 0.001 |
| Smoking history§, n (%) | 0.192 | ||
| Never smokers | 495 (59.5) | 1,365 (57.1) | |
| Ex-smokers | 173 (20.8) | 530 (22.2) | |
| Current-smokers | 159 (19.1) | 485 (20.3) | |
| Missing | 5 (0.6) | 11 (0.4) | |
| Smoking amount (pack-year)* | 14±22 | 12±20 | 0.233 |
| BMI (kg/m2)* | 24±3 | 24±3 | 0.243 |
| PFT* | |||
| FEV1 (L) | 2.3±0.6 | 2.8±0.7 | <0.001 |
| FEV1 (% predicted value) | 91±16 | 93±13 | 0.026 |
| FVC (L) | 3.1±0.8 | 3.5±0.9 | <0.001 |
| FVC (% predicted value) | 90±13 | 92±12 | <0.001 |
| Educational level, n (%) | <0.001 | ||
| Elementary school | 530 (63.7) | 681 (28.5) | |
| Middle school | 132 (15.9) | 405 (16.9) | |
| High school | 122 (14.7) | 755 (31.6) | |
| University | 44 (5.3) | 543 (22.7) | |
| Missing | 4 (0.4) | 7 (0.3) | |
| Level of stress, n (%) | 0.553 | ||
| Little | 193 (23.2) | 359 (15.0) | |
| Some | 388 (46.6) | 1402 (58.6) | |
| Much | 192 (23.1) | 530 (22.2) | |
| Very much | 55 (6.6) | 93 (3.9) | |
| Missing | 4 (0.5) | 4 (0.3) | |
| Comorbidity#, n (%) | |||
| Stroke | 34 (4.1) | 36 (1.5) | <0.001 |
| Ischemic heart disease | 30 (3.6) | 50 (2.1) | 0.020 |
| Hypertension | 321 (38.6) | 593 (24.8) | <0.001 |
| Osteoporosis | 143 (17.2) | 184 (7.7) | <0.001 |
| Depression | 43 (5.2) | 106 (4.4) | 0.443 |
| Lung cancer | 2 (0.2) | 5 (0.2) | 1.000 |
| DM | 136 (16.3) | 212 (8.9) | <0.001 |
| Bronchiectasis | 6 (0.7) | 14 (0.6) | 0.798 |
| Pulmonary tuberculosis | 59 (7.1) | 156 (6.5) | 0.629 |
| COPD | 161 (19.4) | 223 (9.3) | <0.001 |
*, data are presented as mean ± SD. Other variables are presented as a number (percent). §, smoking history was categorized as “current smoker”, “ex-smoker”, or “never smoker”. Current-smoker was defined as a person who had smoked more than 100 cigarettes in their lifetime, and ex-smoker was defined as one who had not smoked in the last 28 days. #, comorbid diseases were ascertained from answers to the question: “Were you diagnosed with a comorbid disease by a doctor?” For example, stroke was ascertained by the question: “Were you diagnosed with stroke by a doctor?” BMI, body mass index; COPD, chronic obstructive pulmonary disease; FEV1, a forced expiratory volume in one second; FVC, a forced vital capacity; DM, diabetes mellitus; PFT, pulmonary function test.