Table 4 presents the M = 2 GEE estimates for both regression sets, using ppm as the exposure measure. For both added fluoride and natural fluoride, the estimates aligned with the set of M = 1 results, only greater in magnitude. For added fluoride, a 1 ppm increase produced a 0.35 per 1,000 increase in diabetes incidence (P < 0.001) and a 0.27% increase in prevalence (P < 0.001), whereas the respective estimates for natural fluoride were 0.73 per 1,000 decline (P < 0.001) and a 0.55% decline (P < 0.001).
GEE regression sets, M = 2
| Outcomes: Diabetes incidence and prevalence, M = 2 (unadjusted exposure in ppm) . | ||||
|---|---|---|---|---|
| Covariates . | Incidence . | Prevalence . | Incidence . | Prevalence . |
| E = 1 . | E = 2 . | E = 1 . | E = 2 . | |
| Added fluoride (in ppm) | 0.35 (0.11)** | 0.27 (0.09)** | – | – |
| Natural fluoride (in ppm) | – | – | −0.73 (0.12)*** | −0.55 (0.09)*** |
| AA physical inactivity | 0.06 (0.01)*** | 0.06 (0.01)*** | 0.05 (0.01)*** | 0.06 (0.01)*** |
| AA obesity | 0.31 (0.01)*** | 0.22 (0.01)*** | 0.31 (0.01)*** | 0.23 (0.01)*** |
| Poverty percent | 0.13 (0.01)*** | 0.10 (0.01)*** | 0.13 (0.01)*** | 0.10 (0.01)*** |
| Fluoridation chemical (yes/no) | ||||
| Sodium fluoride | 0.09 (0.09) | 0.11 (0.07) | – | – |
| Fluorosilicic acid | −0.47 (0.12)*** | −0.36 (0.08)*** | – | – |
| Sodium fluorosilicate | −0.11 (0.11) | −0.15 (0.08) | – | – |
| Years water system fluoridated | −0.006 (0.003)* | −0.004 (0.002)* | – | – |
| Population per square mile (log) | 0.94 (0.08)*** | 0.64 (0.06)*** | 0.86 (0.08)*** | 0.58 (0.06)*** |
| Year = 2010 | −1.88 (0.07)*** | 0.31 (0.05)*** | −1.89 (0.07)*** | 0.30 (0.05)*** |
| Number of counties | 887 | 887 | 923 | 923 |
| Number of observations | 1,774 | 1,774 | 1,846 | 1,846 |
| Outcomes: Diabetes incidence and prevalence, M = 2 (unadjusted exposure in ppm) . | ||||
|---|---|---|---|---|
| Covariates . | Incidence . | Prevalence . | Incidence . | Prevalence . |
| E = 1 . | E = 2 . | E = 1 . | E = 2 . | |
| Added fluoride (in ppm) | 0.35 (0.11)** | 0.27 (0.09)** | – | – |
| Natural fluoride (in ppm) | – | – | −0.73 (0.12)*** | −0.55 (0.09)*** |
| AA physical inactivity | 0.06 (0.01)*** | 0.06 (0.01)*** | 0.05 (0.01)*** | 0.06 (0.01)*** |
| AA obesity | 0.31 (0.01)*** | 0.22 (0.01)*** | 0.31 (0.01)*** | 0.23 (0.01)*** |
| Poverty percent | 0.13 (0.01)*** | 0.10 (0.01)*** | 0.13 (0.01)*** | 0.10 (0.01)*** |
| Fluoridation chemical (yes/no) | ||||
| Sodium fluoride | 0.09 (0.09) | 0.11 (0.07) | – | – |
| Fluorosilicic acid | −0.47 (0.12)*** | −0.36 (0.08)*** | – | – |
| Sodium fluorosilicate | −0.11 (0.11) | −0.15 (0.08) | – | – |
| Years water system fluoridated | −0.006 (0.003)* | −0.004 (0.002)* | – | – |
| Population per square mile (log) | 0.94 (0.08)*** | 0.64 (0.06)*** | 0.86 (0.08)*** | 0.58 (0.06)*** |
| Year = 2010 | −1.88 (0.07)*** | 0.31 (0.05)*** | −1.89 (0.07)*** | 0.30 (0.05)*** |
| Number of counties | 887 | 887 | 923 | 923 |
| Number of observations | 1,774 | 1,774 | 1,846 | 1,846 |
Robust standard errors in parentheses. ***P < 0.001, **P < 0.01, *P < 0.05.