Table 1.
Descriptive statistics of the study population
| Factor or parameter | Both phases | Phase 1 | Phase 2 |
|---|---|---|---|
| Study participants | 1,986 | 876 | 1,110 |
| Households | 557 | 264 | 293 |
| Total N of valid saliva samples | 7,480 | 3,428 | 4,052 |
| Duration of follow-up in days, mean (SD) | 98.4 (29.3) | 86.9 (24.4) | 107.5 (29.6) |
| Total amount of follow-up time for all participants, person-years | 535.5 | 208.5 | 327.0 |
| Gender | |||
| Males | 766 / 39.1% | 346 / 39.7% | 420 / 38.7% |
| Females | 1,192 / 60.9% | 526 / 60.3% | 666 / 61.3% |
| Age in years, mean (SD) | |||
| Children under 18 years of age | 7.4 (4.5) | 7.4 (4.6) | 7.4 (4.5) |
| Adults | 35.5 (11.6) | 34.5 (10.8) | 36.2 (12.1) |
| Age category, N / % of participants | |||
| Children under 18 years of age | 1,170 / 58.8% | 544 / 62.1% | 626 / 56.3% |
| Adults | 816 / 41.2% | 332 / 37.9% | 484 / 43.7% |
| Race, N / % of participants | |||
| Black | 112 / 5.6% | 56 / 6.4% | 56 / 5.0% |
| White | 290 / 14.6% | 148 / 16.9% | 142 / 12.8% |
| Mixed or other | 213 / 10.7% | 197 / 22.5% | 16 / 1.4% |
| Not reported | 1,371 / 69.0% | 475 / 54.2% | 896 / 80.7% |
| Ethnicity, N / % of participants | |||
| Hispanic | 1,864 / 93.9% | 809 / 92.4% | 1,055 / 95.0% |
| Non-Hispanic | 106 / 5.3% | 51 / 5.8% | 55 / 5.0% |
| Not reported | 16 / 0.8% | 16 / 1.8% | 0 / 0.0% |
| Language spoken at home, N / % of participants | |||
| English only | 270 / 13.6% | 121 / 13.8% | 149 / 13.4% |
| Spanish or Portuguese | 1,536 / 77.3% | 716 / 81.7% | 820 / 73.9% |
| Other or not reported | 180 / 9.1% | 39 / 4.5% | 141 / 12.7% |
| Annual household income, N / % of participants | |||
| Less than $ 25,000 | 972 / 48.9% | 462 / 52.7% | 510 / 45.9% |
| Between $ 25,000 and $ 49,000 | 390 / 19.6% | 95 / 10.8% | 295 / 26.6% |
| Between $ 50,000 and $ 74,000 | 88 / 4.4% | 18 / 2.1% | 70 / 6.3% |
| Between $ 75,000 and $ 99,000 | 16 / 0.8% | 8 / 0.9% | 8 / 0.7% |
| $ 100,000 per year or more | 3 / 0.2% | 3 / 0.3% | 0 / 0.0% |
| Not reported | 517 / 26.0% | 290 / 33.1% | 227 / 20.5% |
| Education, N / % of adult participants | |||
| Did not complete high school | 267 / 32.7% | 114 / 34.3% | 153 / 31.6% |
| High school diploma | 255 / 31.3% | 98 / 29.5% | 157 / 32.4% |
| Less than 4 years of college | 133 / 16.3% | 71 / 21.4% | 62 / 12.8% |
| Bachelor’s degree | 44 / 5.4% | 15 / 4.5% | 29 / 6.0% |
| Graduate or professional degree | 43 / 5.3% | 15 / 4.5% | 28 / 5.8% |
| Not reported | 74 / 9.1% | 19 / 5.7% | 55 / 11.4% |
| Home filters, N / % of participants | |||
| Any water filter | 1,079 / 54.3% | 470 / 53.7% | 609 / 54.9% |
| No filter | 892 / 44.9% | 391 / 44.6% | 501 / 45.1% |
| Not reported | 15 / 0.8% | 15 / 1.7% | 0 / 0.0% |
| Swimming, N / % of monthly surveys | |||
| Swimming in pools | 200 / 3.6% | 80 / 3.1% | 120 / 4.1% |
| Swimming in lakes, rivers | 75 / 1.4% | 17 / 0.7% | 58 / 2.0% |
| Swimming in the ocean | 90 / 1.6% | 26 / 1.0% | 64 / 2.2% |
| Consumption of non-boiled tap water, N / % of monthly surveys | |||
| No | 2,705 / 49.2% | 1,279 / 50.1% | 1,426 / 48.5% |
| Yes | 2,617 / 47.6% | 1,145 / 44.9% | 1,472 / 50.0% |
| Not reported | 172 / 3.1% | 128 / 5.0% | 44 / 1.5% |
| Liquid consumption per 24 hours in mL, mean (SD) | |||
| Plain bottled water | 336 (591) | 389 (601) | 291 (578) |
| Boiled tap water and drinks made of it | 286 (501) | 255 (421) | 313 (561) |
| Non-boiled tap water and drinks made of it | 478 (730) | 399 (661) | 545 (778) |
| Total liquid consumption in drinks including tap and bottled water, soda and milk | 2,136 (1,164) | 2,106 (1,165) | 2,160 (1,162) |
| Episodes of gastrointestinal symptoms, N / incidence rate per person-year | |||
| Diarrhea | 147 / 0.27 | 46 / 0.22 | 101 / 0.31 |
| Vomiting | 112 / 0.21 | 35 / 0.17 | 77 / 0.24 |
| Abdominal cramps | 20 / 0.04 | 17 / 0.08 | 3 / 0.01 |
| Gastroenteritis (diarrhea or vomiting or cramps) | 214 / 0.40 | 77 / 0.37 | 137 / 0.42 |
| Combined diarrhea and vomiting | 55 / 0.10 | 13 / 0.06 | 42 / 0.13 |