Demographic and clinical characteristics of patients with COVID-19 by time period*
| Characteristics | Overall (N=1584) | Time period 1 (n=397) | Time period 2 (n=400) | Time period 3 (n=393) | Time period 4 (n=394) | P value |
| Daily cases | 5.7 (3.9) | 6.1 (3.5) | 5.9 (2.7) | 4.0 (2.5) | 8.6 (6.0) | <0.001 |
| Demographic characteristics | ||||||
| Age, years, mean (SD) | 61.58 (19.83) | 66.87 (19.09) | 58.94 (20.39) | 58.79 (20.22) | 61.72 (18.55) | <0.001 |
| Male sex, n (%) | 874 (55.2) | 214 (53.9) | 213 (53.2) | 212 (53.9) | 235 (59.6) | 0.233 |
| Race/ethnicity, n (%) | ||||||
| Asian | 93 (5.9) | 31 (7.8) | 17 (4.2) | 19 (4.8) | 26 (6.6) | <0.001 |
| Hispanic/Latinx | 491 (31.0) | 80 (20.2) | 164 (41.0) | 128 (32.6) | 119 (30.2) | |
| Non-Hispanic black | 262 (16.5) | 71 (17.9) | 60 (15.0) | 76 (19.3) | 55 (14.0) | |
| Non-Hispanic white | 651 (41.1) | 195 (49.1) | 146 (36.5) | 147 (37.4) | 163 (41.4) | |
| Other | 87 (5.5) | 20 (5.0) | 13 (3.2) | 23 (5.9) | 31 (7.9) | |
| Median household income of census tract, median (IQR)† | 36 118 (23 359–54 207) | 42 447 (24 803–58 764) | 29 513 (22 035–50 119) | 31 357 (22 459–51 149) | 38 345 (24 426–55 335) | <0.001 |
| SES index‡ | 56.58 (6.83) | 58.04 (6.98) | 55.32 (6.60) | 56.01 (6.63) | 56.94 (6.85) | <0.001 |
| Clinical characteristics | ||||||
| Elixhauser comorbidity score§, mean (SD) | 10.50 (12.52) | 11.22 (12.45) | 8.86 (11.76) | 10.03 (11.92) | 11.91 (13.69) | 0.003 |
| Obesity, n (%) | 307 (19.4) | 72 (18.1) | 63 (15.8) | 78 (19.8) | 94 (23.9) | 0.031 |
| Hypertension, n (%) | 746 (47.1) | 208 (52.4) | 155 (38.8) | 184 (46.8) | 199 (50.5) | 0.001 |
| Diabetes mellitus, n (%) | 464 (29.3) | 122 (30.7) | 101 (25.2) | 111 (28.2) | 130 (33.0) | 0.095 |
| Prior myocardial infarction or heart failure, n (%) | 388 (24.5) | 101 (25.4) | 81 (20.2) | 84 (21.4) | 122 (31.0) | 0.002 |
| Prior COPD or asthma, n (%) | 296 (18.7) | 77 (19.4) | 72 (18.0) | 64 (16.3) | 83 (21.1) | 0.36 |
*Time periods defined based on quartiles of cumulative cases. Time period 1 ranges from 4 March to 7 May; period 2 from 8 May to 14 July; period 3 from 15 July to 20 October; and period 4 from 21 October to 5 December.
†Median household income was obtained from the American Community Survey 2013–2018. Data were missing for 16% of the sample due to missing data on patient census tract. For these patients, income was imputed as the median value. P value for median household income was obtained via Kruskal-Wallis test.
‡SES index calculated according to AHRQ methodology, standardised to Los Angeles County.
§Elixhauser comorbidity score calculated using the van Walraven method.
AHRQ, Agency for Healthcare Research and Quality; COPD, chronic obstructive pulmonary disease; SES, socioeconomic status.