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Volume 32, Number 8—August 2026
Research
Infections in Infancy and Association with Long-Term Weight Gain and Obesity in Children, Southern California, USA
and Jane C. Lin
Table 1
Maternal and infant characteristics, infant exposures, and weight and obesity outcomes at 10–15 years of age from a study of the effect of infant infections on obesity later in life*
| Characteristics | NMAI, n = 7,594 | IWOT, n = 18,468 | IWAT, n = 20,537 | p value |
|---|---|---|---|---|
| Maternal factors | ||||
| Maternal obesity | 620 (8.2) | 1,811 (9.8) | 2,341 (11) | <0.001 |
| Caesarean section | 2,356 (31) | 5,646 (31) | 6,551 (32) | 0.017 |
| Household income† | <0.001 | |||
| $0–30,000 | 306 (4.0) | 932 (5.0) | 1,060 (5.2) | |
| $30,001–50,000 | 1,722 (23) | 4,622 (25) | 5,404 (26) | |
| $50,001–70,000 | 2,103 (28) | 5,473 (30) | 6,063 (30) | |
| $70,001–90,000 | 1,674 (22) | 3,824 (21) | 4,174 (20) | |
| >$90,000 | 1,789 (24) | 3,617 (20) | 3,836 (19) | |
| Race/ethnicity | <0.001 | |||
| Asian/Pacific Islander | 1,520 (20) | 2,638 (14) | 2,363 (12) | |
| Black | 491 (6.5) | 1,426 (7.7) | 1,527 (7.4) | |
| Hispanic | 3,002 (40) | 9,217 (50) | 10,968 (53) | |
| White | 2,401 (32) | 4,852 (26) | 5,357 (26) | |
| Other/unknown |
180 (2.4) |
335 (1.8) |
322 (1.6) |
|
| Infant factors | ||||
| Sex | ||||
| F | 4,071 (54) | 9,327 (51) | 9,337 (45) | <0.001 |
| M | ||||
| Macrosomia, birthweight >4 kg | 693 (9.1) | 1,781 (9.6) | 2,376 (12) | <0.001 |
| Age at first antibiotic exposure, mo | ||||
| <6 | 8,339 (41) | |||
| 6–12 | 12,198 (59) | |||
| No. antibiotic courses by age 12 mo | ||||
| 0 | 7,594 (100) | 18,468 (100) | NA | |
| 1 | NA | NA | 12,523 (61) | |
| 2 | NA | NA | 5,292 (26) | |
| >3 | NA | NA | 2,722 (13) | |
| No. clinical infections by age 12 mo | <0.001 | |||
| 0 | 7,594 (100) | 0 (0) | 0 (0) | |
| 1 | NA | 8,690 (47) | 3,429 (17) | |
| 2 | NA | 5,598 (30) | 5,545 (27) | |
| 3 | NA | 2,749 (15) | 5,173 (25) | |
| >4 | NA | 1,431 (7.7) | 6,390 (31) | |
| Breastfeeding status | <0.001 | |||
| Nonexclusive | 2,148 (28) | 5,257 (28) | 5,802 (28) | |
| Exclusive | 2,619 (34) | 5,307 (29) | 5,259 (26) | |
| Nonbreastfed | 2,642 (35) | 7,413 (40) | 8,958 (44) | |
| Unknown |
185 (2.4) |
491 (2.7) |
518 (2.5) |
|
| Outcomes at 10–15 years of age | ||||
| Age, y, median (IQR) | 10.0 (10.0–11.0) | 10.0 (10.0–11.0) | 10.0 (10.0–10.0) | <0.001 |
| Height, cm, median (IQR) | 145.0 (139.7–151.1) | 145.0 (139.7–151.3) | 145.0 (139.7–151.1) | 0.5 |
| Weight, kg, median (IQR) | 39.6 (33.0–49.2) | 41.0 (33.8–50.7) | 41.5 (34.2–52.0) | <0.001 |
| Obesity | 1,485 (20) | 4,384 (24) | 5,564 (27) | <0.001 |
| BMI subcategories | <0.001 | |||
| Normal, 5th–85th percentile | 4,523 (60) | 10,073 (55) | 10,682 (52) | |
| Underweight, <5 percentile | 332 (4.4) | 674 (3.6) | 585 (2.8) | |
| Overweight, 85–95 percentile | 1,254 (17) | 3,337 (18) | 3,706 (18) | |
| Class I obesity‡ | 983 (13) | 2,833 (15) | 3,527 (17) | |
| Class II obesity‡ | 364 (4.8) | 1,124 (6.1) | 1,456 (7.1) | |
| Class III obesity‡ | 138 (1.8) | 427 (2.3) | 581 (2.8) |
*Values no. (%) except as indicated. IWAT, clinical infection in infancy with antimicrobial drug treatment; IWOT, clinical infection in infancy without antimicrobial drug treatment; NA, not applicable; NMAI, no clinical infections in infancy. †Income bracket estimated by the mean household income for area of residence ‡Standardized for age and gender. Childhood obesity categories class I, BMI >95%–<120% of 95 percentile; class II, BMI >120%–<140% of 95 percentile; class III, >140% of 95 percentile.