Table 1.
Background characteristics of cases and controls, India, May-July 2021.
| Characteristics | Cases (%) | Controls (%) | P-value |
|---|---|---|---|
| Median age in years (IQR) |
(n = 1143) 60 (52-69) |
(n = 2541) 55 (50-62) |
<0.001 |
| Gender | (n = 1143) | (n = 2541) | |
| Male | 654 (57.2) | 1590 (62.6) | 0.007 |
| Female | 489 (42.8) | 950 (37.4) | |
| Residence | (n = 1138) | (n = 2520) | |
| Rural | 560 (49.2) | 941 (37.3) | <0.001 |
| Urban | 578 (50.8) | 1579 (62.7) | |
| Occupation | (n = 1143) | (n = 2538) | |
| Unemployed/student/homemaker | 574 (50.2) | 901 (35.5) | <0.001 |
| Retired | 139 (12.2) | 333 (13.1) | |
| Agriculture | 121 (10.6) | 262 (10.3) | |
| Professional/technical/administrative/management | 89 (7.8) | 374 (14.7) | |
| Skilled manual | 85 (7.4) | 272 (10.7) | |
| Unskilled manual | 65 (5.7) | 158 (6.2) | |
| Sales and services | 53 (4.6) | 167 (6.6) | |
| Clerical | 17(1.5) | 71 (2.8) | |
| Formal education | (n = 1142) | (n = 2541) | |
| Illiterate | 225 (19.7) | 426 (16.8) | <0.001 |
| Primary school | 195 (17.1) | 248(9.8) | |
| Middle school | 210 (18.4) | 347 (13.7) | |
| Secondary school | 185 (16.2) | 528 (20.8) | |
| Higher secondary school (11th and 12th std) | 122 (10.7) | 335 (13.2) | |
| Graduation | 152 (13.3) | 467 (18.4) | |
| Post-graduation and above | 53 (4.6) | 190 (7.5) | |
| Smoking status | (n = 1114) | (n = 2522) | |
| Never smoked | 915 (82.1) | 2083 (82.6) | 0.43 |
| Former smoker | 118 (10.6) | 237 (9.4) | |
| Current smoker | 81 (7.3) | 202 (8.0) | |
| Any pre-existing comorbidities |
(n = 1143) 781 (68.3) |
(n = 2541) 1336 (52.6) |
<0.001 |
| Type of pre-existing comorbidity | |||
| Hypertension |
(n = 781) 528 (67.6) |
(n = 1335) 678 (50.8) |
<0.001 |
| Diabetes mellitus |
(n = 781) 501 (64.1) |
(n = 1333) 651 (48.8) |
<0.001 |
| Heart disease |
(n = 778) 135 (17.3) |
(n = 1335) 195 (14.6) |
0.09 |
| Asthma |
(n = 780) 50 (6.4) |
(n = 1333) 49 (3.7) |
0.004 |
| Lung disease other than asthmaa |
(n = 767) 49 (6.4) |
(n = 1335) 30 (2.2) |
<0.001 |
| Any malignancy |
(n = 780) 45 (5.8) |
(n = 1336) 260 (19.5) |
<0.001 |
| Liver disease |
(n = 780) 33 (4.2) |
(n = 1336) 35 (2.6) |
0.04 |
| Any immunodeficiency disorder |
(n = 779) 29 (3.7) |
(n = 1332) 45 (3.4) |
0.68 |
| Kidney disease |
(n = 781) 63 (8.1) |
(n = 1334) 69 (5.2) |
0.008 |
| Active tuberculosis |
(n = 780) 10 (1.3) |
(n = 1330) 10 (0.7) |
0.23 |
a
Includes all conditions affecting the lungs with the exclusion of asthma
IQR = interquartile range.