Table 1.
Comparison of selected characteristics in survey responders and nonresponders.
| Characteristic | Responders (n = 7,785) | Nonresponders (n = 15,525) | p-Value |
|---|---|---|---|
| Continuous composite UNGD activity metric, mean ± sd | –0.02 ± 1.80 | 0.01 ± 2.78 | 0.26a |
| UNGD activity, n (%) | |||
| Quartile 1 | 2,052 (26.4) | 3,775 (24.3) | < 0.001b |
| Quartile 2 | 1,828 (23.5) | 3,996 (25.7) | |
| Quartile 3 | 2,017 (25.9) | 3,814 (24.6) | |
| Quartile 4 | 1,888 (24.3) | 3,940 (25.4) | |
| Charlson index, mean ± sd | 3.43 ± 2.76 | 2.52 ± 2.65 | < 0.001a |
| Charlson index stratified by quartiles of UNGD activity, mean ± sd | |||
| Quartile 1 | 3.27 ± 2.61 | 2.46 ± 2.46 | |
| Quartile 2 | 3.37 ± 2.71 | 2.48 ± 2.57 | NA |
| Quartile 3 | 3.61 ± 2.83 | 2.68 ± 2.85 | |
| Quartile 4 | 3.47 ± 2.86 | 2.48 ± 2.70 | |
| p < 0.001c | p < 0.001c | ||
| Notes: NA, not applicable; sd, standard deviation; UNGD, unconventional natural gas development. Patients who lived outside Pennsylvania were excluded (n = 390). UNGD activity was averaged over 90 days before the survey. ap-Value computed using Student’s t-test. bp-Value computed using Chi-squared test. cWithin responders and nonresponders separately, p-values were computed with one-way analysis of variance (ANOVA) to compare mean Charlson index across quartiles of UNGD. | |||