Table 2.
Linear regression coefficients (standard error) for change in semen quality endpoints by total urinary BPA concentration, LIFE Study
| Semen quality endpointa,b | Unadjusted modelc
|
Adjusted modelc,d
|
||
|---|---|---|---|---|
| BPA concentration β (SE) | p-value | BPA concentration β (SE) | p-value | |
| General characteristics | ||||
| Volume (mL) | 0.01 (0.03) | 0.85 | 0.06 (0.03) | 0.07 |
| Straw distance (mm) | 0.01 (0.04) | 0.71 | 0.03 (0.04) | 0.52 |
| Sperm concentration (x106/mL) | −0.02 (0.10) | 0.83 | −0.07 (0.12) | 0.56 |
| Total sperm count (x 106/ejaculate) | 0.02 (0.15) | 0.91 | 0.11 (0.18) | 0.54 |
| Hypo-osmotic swollen (%) | 0.43 (0.38) | 0.26 | −0.42 (0.48) | 0.38 |
| Sperm motility | ||||
| Average path velocity (μm/sec) | 0.11 (0.31) | 0.73 | −0.09 (0.38) | 0.81 |
| Straight line velocity (μm/sec) | −0.03 (0.30) | 0.93 | −0.06 (0.36) | 0.87 |
| Curvilinear velocity (μm/sec) | 0.08 (0.54) | 0.88 | −0.22 (0.67) | 0.74 |
| Amplitude head displacement (μm) | −0.00 (0.04) | 0.92 | −0.06 (0.05) | 0.23 |
| Beat cross frequency (Hz) | −0.32 (0.18) | 0.08 | 0.06 (0.23) | 0.79 |
| Straightness (%) | −0.27 (0.29) | 0.35 | 0.04 (0.38) | 0.91 |
| Linearity (%) | −0.19 (0.29) | 0.52 | 0.00 (0.37) | 0.99 |
| Percent motility (%) | −0.01 (0.08) | 0.93 | −0.04 (0.10) | 0.65 |
| Sperm head measurements | ||||
| Length (μm) | 0.00 (0.00) | 0.17 | 0.00 (0.00) | 0.17 |
| Area (μm2) | 0.02 (0.03) | 0.50 | 0.07 (0.04) | 0.10 |
| Width (μm) | −0.01 (0.01) | 0.46 | 0.01 (0.01) | 0.43 |
| Perimeter (μm) | 0.02 (0.02) | 0.26 | 0.04 (0.02) | 0.10 |
| Elongation factor (%) | −0.29 (0.20) | 0.13 | −0.11 (0.25) | 0.66 |
| Acrosome area of head (%) | 0.09 (0.18) | 0.64 | 0.19 (0.22) | 0.40 |
| Morphology | ||||
| Strict criteria (%) | −0.04 (0.21) | 0.84 | 0.28 (0.27) | 0.31 |
| Traditional normal (%) | 0.09 (0.62) | 0.89 | 1.22 (0.78) | 0.12 |
| Amorphous (%) | 0.04 (0.05) | 0.40 | 0.02 (0.07) | 0.73 |
| Round (%) | 0.03 (0.04) | 0.15 | 0.08 (0.05) | 0.14 |
| Pyriform (%) | −0.02 (0.05) | 0.77 | −0.03 (0.07) | 0.62 |
| Bicephalic (%) | −0.03 (0.05) | 0.58 | −0.05 (0.06) | 0.43 |
| Taper (%) | 0.03 (0.05) | 0.50 | −0.02 (0.06) | 0.73 |
| Megalo head (%) | 0.09 (0.04) | 0.81 | 0.06 (0.04) | 0.15 |
| Micro head (%) | −0.01 (0.04) | 0.84 | −0.04 (0.04) | 0.35 |
| Neck and midpiece abnormalities (%) | −0.00 (0.01) | 0.85 | −0.01 (0.02) | 0.73 |
| Coiled tail (%) | −0.03 (0.02) | 0.25 | −0.05 (0.03) | 0.09 |
| Other tail abnormalities (%) | −0.05 (0.04) | 0.18 | −0.08 (0.04) | 0.07 |
| Cytoplasmic droplet (%) | −0.06 (0.05) | 0.29 | −0.13 (0.07) | 0.05 |
| Immature sperm (n) | 0.00 (0.05) | 0.92 | 0.00 (0.07) | 0.95 |
| Sperm chromatin structure assay | ||||
| DNA fragmentation index | −0.07 (0.02) | 0.00 | −0.05 (0.03) | 0.04 |
| High DNA stainability | 0.00 (0.02) | 0.98 | 0.03 (0.03) | 0.28 |
NOTE: All beta coefficients and standard errors were rounded to two decimal places.
All semen quality endpoints were transformed using the Box-Cox transformation.
Separate models were run for each individual endpoint.
When modeling the association between BPA and semen quality endpoints that were assessed in both semen samples, the association between first and second samples was accounted for by using Generalized Estimating Equations (GEE).
Multivariate linear regression models were adjusted for age (continuous), abstinence time (continuous), alcohol consumption (categorical), body mass index (continuous), creatinine (continuous), education (categorical), income (categorical), previously fathered pregnancy (continuous), serum cotinine (continuous), study site (categorical), and race/ethnicity (categorical).