Table 1

Demographic and clinical characteristics of patients with COVID-19 by time period*

CharacteristicsOverall
(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 cases5.7 (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 (%)
 Asian93 (5.9)31 (7.8)17 (4.2)19 (4.8)26 (6.6)<0.001
 Hispanic/Latinx491 (31.0)80 (20.2)164 (41.0)128 (32.6)119 (30.2)
 Non-Hispanic black262 (16.5)71 (17.9)60 (15.0)76 (19.3)55 (14.0)
 Non-Hispanic white651 (41.1)195 (49.1)146 (36.5)147 (37.4)163 (41.4)
 Other87 (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.