Table 2.
Univariate associations of thermal pain measures and incidence rates of first-onset TMD
| Distribution of risk factor at enrolment | Site-adjusted(1) TMD incidence rate (% of people per annum) according to tercile of risk factor | Standardized hazard ratios (95%CI) adjusted for: | Imputed estimates with adjustment for study site + demographics (5) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Stimulus | Units and potential range | n | mean (sd) [1st, 2nd tercile] | Lower | Mid | Upper | Study site (2) | Study site + demographics(3) | P-value(4) | n | Hazard ratio (95%CI) | P-value(4) |
| Heat pain threshold(6) | °C, 32–52 | 2103 | 42.2 (3.1) [41.0; 44.0] | 3.9 | 4.4 | 3.7 | 1.00 (0.86, 1.15) | 1.00 (0.86, 1.16) | 0.97 | 2103 | 1.03 (0.88, 1.20) | 0.720 |
| Heat pain tolerance(6) | °C, 32–52 | 2455 | 46.2 (2.4) [45.4; 47.2] | 4.2 | 4.3 | 3.7 | 1.05 (0.92, 1.18) | 1.03 (0.91, 1.16) | 0.620 | 2567 | 1.06 (0.92, 1.21) | 0.410 |
| Single stimulus ratings | ||||||||||||
| 46°C | rating, 0–100 | 2429 | 36.7 (32.0) [10.0; 50.0] | 3.1 | 3.9 | 5.0 | 1.12 (0.99, 1.27) | 1.11 (0.98, 1.25) | 0.094 | 2539 | 1.11 (0.97, 1.27) | 0.120 |
| 48°C | rating, 0–100 | 2400 | 45.1 (32.9) [20.0; 60.0] | 3.9 | 4.0 | 4.5 | 1.05 (0.92, 1.19) | 1.04 (0.91, 1.17) | 0.590 | 2539 | 1.14 (0.99, 1.30) | 0.062 |
| 50°C | rating, 0–100 | 2322 | 57.4 (33.9) [35.0; 80.0] | 4.2 | 3.8 | 4.2 | 1.05 (0.92, 1.19) | 1.04 (0.91, 1.18) | 0.550 | 2539 | 1.07 (0.93, 1.23) | 0.320 |
| Ratings of 10 stimuli: area under curve | ||||||||||||
| 46°C | ratings, 0–1000 | 2030 | 347.8 (236.4) [185.0; 467.5] | 3.5 | 4.1 | 3.5 | 1.00 (0.86, 1.16) | 1.05 (0.90, 1.21) | 0.530 | 2539 | 1.16 (1.01, 1.32) | 0.033 |
| 48°C | ratings, 0–1000 | 1701 | 412.2 (242.2) [255.0; 557.5] | 2.6 | 3.1 | 3.6 | 1.10 (0.92, 1.29) | 1.14 (0.96, 1.34) | 0.130 | 2539 | 1.22 (1.06, 1.41) | 0.006 |
| 50°C | ratings, 0–1000 | 1258 | 466.9 (248.7) [330.0; 630.0] | 2.2 | 2.9 | 3.1 | 1.16 (0.94, 1.40) | 1.20 (0.98, 1.46) | 0.076 | 2539 | 1.23 (1.05, 1.41) | 0.006 |
| Maximum rating from among 10 stimuli | ||||||||||||
| 46°C | ratings, 0–1000 | 2534 | 57.1 (33.7) [35.0; 80.0] | 3.8 | 3.9 | 4.6 | 1.11 (0.97, 1.26) | 1.12 (0.97, 1.28) | 0.099 | 2539 | 1.16 (1.01, 1.32) | 0.032 |
| 48°C | ratings, 0–1000 | 2509 | 68.2 (32.2) [53.0; 95.0] | 3.3 | 4.1 | 5.2 | 1.22 (1.06, 1.39) | 1.23 (1.06, 1.41) | 0.004 | 2539 | 1.23 (1.06, 1.42) | 0.005 |
| 50°C | ratings, 0–1000 | 2420 | 77.6 (29.5) [75.0; 100.0] | . | . | . | 1.21 (1.05, 1.39) | 1.21 (1.04, 1.40) | 0.009 | 2539 | 1.24 (1.06, 1.44) | 0.005 |
| Thermal aftersensations | ||||||||||||
| 15 s, 46°C | rating, 0–100 | 2498 | 0.5 (0.4) [0.0; 1.0] | . | . | . | 1.08 (0.94, 1.22) | 1.09 (0.95, 1.24) | 0.190 | 2504 | 1.07 (0.93, 1.22) | 0.320 |
| 30 s, 46°C | rating, 0–100 | 2500 | 0.4 (0.4) [0.0; 1.0] | . | . | . | 1.14 (1.00, 1.28) | 1.15 (1.00, 1.30) | 0.036 | 2504 | 1.12 (0.98, 1.27) | 0.095 |
| 15 s, 48°C | rating, 0–100 | 2501 | 0.6 (0.4) [0.0; 1.0] | . | . | . | 1.17 (1.01, 1.33) | 1.20 (1.04, 1.37) | 0.011 | 2504 | 1.17 (1.01, 1.34) | 0.026 |
| 30 s, 48°C | rating, 0–100 | 2502 | 0.5 (0.4) [0.0; 1.0] | . | . | . | 1.12 (0.97, 1.27) | 1.12 (0.98, 1.28) | 0.088 | 2504 | 1.11 (0.96, 1.26) | 0.140 |
| 15 s, 50°C | rating, 0–100 | 2405 | 0.7 (0.4) [0.0; 1.0] | . | . | . | 1.13 (0.98, 1.29) | 1.14 (0.99, 1.31) | 0.067 | 2504 | 1.13 (0.98, 1.30) | 0.081 |
| 30 s, 50°C | rating, 0–100 | 2401 | 0.5 (0.4) [0.0; 1.0] | . | . | . | 1.16 (1.01, 1.33) | 1.17 (1.02, 1.34) | 0.023 | 2504 | 1.14 (0.99, 1.30) | 0.063 |
| Temporal summation: highest minus first rating | ||||||||||||
| 46°C | Δ ratings, 0–100 | 2302 | 20.2 (26.2) [10.0; 30.0] | 3.69 | 4.15 | 4.07 | 0.99 (0.86, 1.12) | 1.00 (0.87, 1.14) | 0.980 | 2539 | 1.07 (0.94, 1.20) | 0.310 |
| 48°C | Δ ratings, 0–100 | 2207 | 25.2 (25.8) [10.0; 30.0] | 3.1 | 3.83 | 4.11 | 1.12 (0.98, 1.28) | 1.11 (0.96, 1.26) | 0.130 | 2539 | 1.07 (0.94, 1.20) | 0.300 |
| 50°C | Δ ratings, 0–100 | 1922 | 25.5 (25.4) [10.0; 30.0] | 2.8 | 2.9 | 4.2 | 1.24 (1.07, 1.43) | 1.25 (1.07, 1.44) | 0.003 | 2539 | 1.14 (1.00, 1.28) | 0.039 |
| Temporal summation: slope of line for first three ratings | ||||||||||||
| 46°C | β coefficient | 2304 | 6.7 (10.2) [2.5; 7.5] | 4.41 | 3.44 | 4.25 | 0.99 (0.86, 1.13) | 0.99 (0.86, 1.13) | 0.860 | 2539 | 1.04 (0.91, 1.17) | 0.570 |
| 48°C | β coefficient | 2211 | 8.1 (10.9) [2.5; 10.0] | 3.19 | 3.43 | 4.59 | 1.12 (0.99, 1.26) | 1.09 (0.97, 1.22) | 0.140 | 2539 | 1.08 (0.96, 1.20) | 0.180 |
| 50°C | β coefficient | 1922 | 9.0 (12.1) [2.5; 10.0] | 3.14 | 3.41 | 3.58 | 1.15 (1.01, 1.31) | 1.14 (1.00, 1.29) | 0.050 | 2539 | 1.12 (1.00, 1.26) | 0.044 |
Adjusted rates computed using Poisson regression controlling for study site (categorical variable, 4 levels). Estimated rate is for reference study site (UB). Empty cells in these columns reflect variables for which a tercile is equal to either a floor (“0”) or ceiling (“100”) value, thus precluding calculation of incidence rate by tercile.
Hazard ratios represent relative increase in rate of TMD associated with an increase of 1 s.d. in risk factor. Computed using Cox proportional hazard regression model controlling for study site (categorical variable, 4 levels).
As for footnote 2, with additional adjustment for age (in years as a continuous variable), gender (categorical, 2 levels), race/ethnicity (categorical, 5 levels) and lifetime US residence (categorical, 2 levels).
P-value evaluating null hypothesis that the hazard ratio equals one.
As for footnote 3, with inclusion of imputed TMD rates for subjects lost to follow-up or with questionable examiner-classification
Negative z-score were used for standardized hazard ratios which therefore represent increase in incidence associated with reduction of 1 SD in threshold