Table 3.
Estimated slopes and net associations between continuous smoothed exposure to current and lifetime tobacco and marijuana and pulmonary function
|
Smoking exposure Estimate type* |
Units | Forced Expiratory Volume in 1 second (FEV1) |
Forced Vital Capacity (FVC) |
||
|---|---|---|---|---|---|
| Adjusted† estimate (95% CI) |
p-value | Adjusted† estimate (95% CI) |
p-value | ||
| Current Marijuana Exposure | |||||
| Test of overall association | -- | -- | .056 | -- | <.001 |
| Test of non-linearity | -- | -- | .025 | -- | .035 |
| Slope at 5 episodes/month | ml per episode/month | 0.8 (−1.4 – 3.1) | .47 | 2.8 (0.4 – 5.1) | .023 |
| Slope at 10 episode/month | ml per episode/month | 2.6 (−0.3 – 5.4) | .074 | 3.7 (0.7 – 6.6) | .016 |
| Slope at 20 episode/month | ml per episode/month | −3.2 (−5.8 – −0.6) | .017 | −1.5 (−4.2 – 1.3) | .30 |
| Slope at 40 episode/month | ml per episode/month | --‡ | --‡ | --‡ | --‡ |
| Net association at 5 episode/month | ml | 4.1 (−7.1 – 15) | .47 | 14 (1.9 – 26) | .023 |
| Net association at 10 episode/month | ml | 11 (−6.2 – 29) | .21 | 29 (11 – 48) | .002 |
| Net association at 20 episode/month | ml | 14 (−4.7 – 32) | .14 | 43 (23 – 63) | <.001 |
| Net association at 40 episode/month | ml | --‡ | --‡ | --‡ | --‡ |
| Lifetime Marijuana Exposure | |||||
| Test of overall association | -- | -- | <.001 | <.001 | |
| Test of non-linearity | -- | -- | <.001 | <.001 | |
| Slope at 2 joint-years | ml per joint-year | 13 (6.4 – 20) | <.001 | 20 (12 – 27) | <.001 |
| Slope at 7 joint-years | ml per joint-year | −0.4 (−2.6 – 1.8) | .74 | 0.0 (−2.4 – 2.5) | .97 |
| Slope at 20 joint-years | ml per joint-year | −2.2 (−4.6 – 0.3) | .079 | 1.0 (−1.8 – 3.7) | .49 |
| Slope at 50 joint-years | ml per joint-year | −2.2 (−4.6 – 0.3) | .079 | 1.0 (−1.8 – 3.7) | .49 |
| Net association at 2 joint-years | ml | 30 (8.4 – 53) | .007 | 59 (35 – 83) | <.001 |
| Net association at 7 joint-years | ml | 53 (28 – 79) | <.001 | 64 (36 – 92) | <.001 |
| Net association at 20 joint-years | ml | 27 (−10 – 64) | .16 | 76 (34 – 117) | <.001 |
| Net association at 50 joint-years | ml | −39 (−141 – 64) | .46 | 104 (−12 – 220) | .078 |
| Current Tobacco Exposure | |||||
| Test of overall association | -- | <.001 | -- | .003 | |
| Test of non-linearity | -- | .29 | -- | .73 | |
| Slope at 5 cigarettes/day | ml per cigarettes/day | −0.2 (−2.3 – 1.9) | .85 | −0.8 (−3.1 – 1.4) | .46 |
| Slope at 10 cigarettes/day | ml per cigarettes/day | −2.8 (−4.8 – −0.7) | .007 | −1.3 (−3.4 – 0.9 | .25 |
| Slope at 20 cigarettes/day | ml per cigarettes/day | −1.1 (−2.7 – 0.5) | .165 | −1.9 (−3.6 – −0.2) | .025 |
| Slope at 40 cigarettes/day | ml per cigarettes/day | −1.1 (−2.7 – 0.5) | .165 | −1.9 (−3.6 – −0.2) | .025 |
| Net association at 5 cigarettes/day | ml | −1.0 (−11 – 9.4) | .85 | −4.2 (−15 – 6.9) | .46 |
| Net association at 10 cigarettes/day | ml | −6.3 (−23 – 11) | .47 | −9.1 (−27 – 8.9) | .32 |
| Net association at 20 cigarettes/day | ml | −34 (−53 – −16) | <.001 | −26 (−46 – −7.0) | .008 |
| Net association at 40 cigarettes/day | ml | −57 (−92 – −22) | <.001 | −84 (−136 – −32) | .002 |
| Lifetime Tobacco Exposure | |||||
| Test of overall association | -- | -- | <.001 | <.001 | |
| Test of non-linearity | -- | -- | .98 | .85 | |
| Slope at 2 pack-years | ml per pack-year | −6.5 (−12 – −1.2) | .016 | −3.5 (−9.3 – 2.4) | .25 |
| Slope at 7 pack-years | ml per pack-year | −7.0 (−10 – −3.7) | <.001 | −5.5 (−9.3 – −1.8) | .004 |
| Slope at 20 pack-years | ml per pack-year | −6.6 (−8.4 – −4.7) | <.001 | −4.5 (−6.6 – −2.3) | <.001 |
| Slope at 50 pack-years | ml per pack-year | −6.6 (−8.4 – −4.7) | <.001 | −4.5 (−6.6 – −2.3) | <.001 |
| Net association at 2 pack-years | ml | −13 (−23 – −2.4) | .016 | −6.9 (−19 – 4.8) | .25 |
| Net association at 7 pack-years | ml | −46 (−72 – −21) | <.001 | −28 (−57 – 0.1) | .05 |
| Net association at 20 pack-years | ml | −135 (−166 – −104) | <.001 | −95 (−130 – −59) | <.001 |
| Net association at 50 pack-years | ml | −332 (−401 – −263) | <.001 | −229 (−310 – −147) | <.001 |
Associations between continuous current and lifetime exposure measurements and pulmonary function were modeled via cubic splines (see Methods), and the estimates presented here describe the same analyses illustrated in Figure 2. The estimates presented are for slope (reflecting the incremental difference in pulmonary function observed with 1 unit of additional tobacco or marijuana smoking exposure) and net association (reflecting the net observed difference between persons with a particular level of consumption and persons with none). As illustrated in Figure 2, slopes vary at different exposure levels (i.e., associations are not constrained to be linear).
All estimates are from the 2 models (one each for FEV1 and FVC) illustrated in Figure 2, and include all four smoking exposure types (current and lifetime tobacco and marijuana). Mixed models with a random intercept and a random 3-knot age spline were used to adjust for repeated measures, and fixed effects were included for year, center and center-year (their interaction), race-sex category, education, asthma; cubic splines for age, height, waist circumference, second hand smoke exposure, PM10 and PM2.5; and interactions between the age spline variables and race-sex, asthma, waist spline variables, and height spline variables.
Data are not available at this exposure level.
CI – Confidence interval; FEV1 – Forced expiratory volume in 1 second; FVC – Forced vital capacity