Table 2. Study Population Characteristics.
| Variable | Participants, No. (%)a | P value | |
|---|---|---|---|
| Cases | Controls | ||
| Total | 175 688 | 43 922 | |
| Sex | |||
| Female | 116 308 (66.2) | 29 077 (66.2) | >.99 |
| Male | 59 380 (33.8) | 14 845 (33.8) | |
| Age, y | |||
| 18-29 | 21 244 (12.1) | 5311 (12.1) | >.99 |
| 30-39 | 31 888 (18.2) | 7972 (18.2) | |
| 40-49 | 47 032 (26.8) | 11 758 (26.8) | |
| 50-59 | 37 960 (21.6) | 9490 (21.6) | |
| 60-69 | 24 796 (14.1) | 6199 (14.1) | |
| ≥70 | 12 768 (7.3) | 3192 (7.3) | |
| Population in the area of residence | |||
| <5000 inhabitants | 44 828 (25.5) | 11 207 (25.5) | >.99 |
| 5000-19 999 inhabitants | 13 984 (8.0) | 3496 (8.0) | |
| 20 000-99 999 inhabitants | 17 800 (10.1) | 4450 (10.1) | |
| Over 100 000 inhabitants | 61 956 (35.3) | 15 489 (35.3) | |
| Greater Paris area | 37 120 (21.1) | 9280 (21.1) | |
| Region of residence | |||
| Ile-de-France | 39 848 (22.7) | 9962 (22.7) | >.99 |
| Auvergne-Rhône-Alpes | 23 384 (13.3) | 5846 (13.3) | |
| Occitanie | 17 860 (10.2) | 4465 (10.2) | |
| Provence-Alpes-Côte d’Azur and Corsica | 15 788 (9.0) | 3947 (9.0) | |
| Nouvelle-Aquitaine | 15 132 (8.6) | 3783 (8.6) | |
| Grand Est | 15 336 (8.7) | 3834 (8.7) | |
| Hauts-de-France | 14 800 (8.4) | 3700 (8.4) | |
| Pays de la Loire | 8580 (4.9) | 2145 (4.9) | |
| Bretagne | 8324 (4.7) | 2081 (4.7) | |
| Normandie | 6124 (3.5) | 1531 (3.5) | |
| Bourgogne-Franche-Comté | 5876 (3.3) | 1469 (3.3) | |
| Centre-Val de Loire | 4636 (2.6) | 1159 (2.6) | |
| Education level | |||
| No diploma | 3682 (2.1) | 767 (1.7) | <.001 |
| Pre–high school diploma | 25 982 (14.8) | 7722 (17.6) | |
| High school diploma | 31 763 (18.1) | 10 559 (24.0) | |
| Bachelor’s degree | 62 869 (35.8) | 16 340 (37.2) | |
| Master’s degree or higher | 51 392 (29.3) | 8534 (19.4) | |
| Health care worker | 19 400 (11.0) | 3021 (6.9) | <.001 |
| Health conditions | |||
| Diabetes | 6149 (3.5) | 2304 (5.2) | <.001 |
| Hypertension | 20 480 (11.7) | 5773 (13.1) | <.001 |
| Chronic respiratory disease | 14 639 (8.3) | 3132 (7.1) | <.001 |
| Body mass indexb | |||
| Healthy weight (≥18.5 or <25) | 89 350 (50.9) | 20 909 (47.6) | <.001 |
| Underweight (<18.5) | 5414 (3.1) | 1880 (4.3) | |
| Overweight (≥25 &<30) | 52 848 (30.1) | 13 111 (29.9) | |
| Obesity (≥30) | 28 074 (16) | 8022 (18.3) | |
| Housing | |||
| Individual house | 106 790 (60.8) | 25 775 (58.7) | <.001 |
| Apartment | 68 217 (38.8) | 18 004 (41.0) | |
| Other | 681 (0.4) | 143 (0.3) | |
| Sharing household with a child of any age and school level | 82 484 (46.9) | 19 652 (44.7) | <.001 |
| Sharing household with a child, by school level | |||
| Daycare | 4946 (2.8) | 928 (2.1) | <.001 |
| Professional in-home caregiver | 5779 (3.3) | 904 (2.1) | <.001 |
| Preschool | 16 478 (9.4) | 3327 (7.6) | <.001 |
| Primary school | 29 039 (16.5) | 6185 (14.1) | <.001 |
| Middle school | 26 790 (15.2) | 6183 (14.1) | <.001 |
| High school | 21 989 (12.5) | 5447 (12.4) | .54 |
| Study period (onset date)c | |||
| 1 (October 1, 2020) | 7308 (4.2) | 1827 (4.2) | |
| 2 (December 4, 2020) | 19 636 (11.2) | 4909 (11.2) | |
| 3 (April 9, 2021) | 9008 (5.1) | 2252 (5.1) | |
| 4 (June 14, 2021) | 11 264 (6.4) | 2816 (6.4) | |
| 5 (August 14, 2021) | 4820 (2.7) | 1205 (2.7) | |
| 6 (October 02, 2021) | 11 248 (6.4) | 2812 (6.4) | |
| 7 (December 20, 2021) | 44 136 (25.1) | 11 034 (25.1) | |
| 8 (March 18, 2022) | 39 652 (22.6) | 9913 (22.6) | |
| 9 (May 20, 2022-October 2, 2022) | 28 616 (16.3) | 7154 (16.3) | |
Cases were adults recently diagnosed with ongoing SARS-CoV-2 infection who were invited by email by the national health insurance system. The controls are adults from the general population matched for age, sex, size of the population in the area of residence, region, and calendar week, who had never tested positive for SARS-CoV-2 until February 2021, when eligibility was extended to all adults without ongoing SARS-CoV-2 infection. One control was matched with 4 cases on age, sex, region, population size of the area of residence, and week of exposure with a bootstrapping procedure to generate 100 databases for each of the study periods to account for the random selection of cases. The numbers indicated are the means for the 100 databases generated for each period by bootstrapping with replacement of sets of 1 control for 4 cases, summed over the 9 periods.
Calculated as weight in kilograms divided by height in meters squared.
Study periods based on changes in incidence, the principal circulating strain, and major nonpharmaceutical interventions.