The association between ambient temperature and sperm quality in Wuhan, China

Table 4 Interaction effects of environmental PM_2.5 and temperature on the percentage of normal sperm morphology (%) at five exposure windows

Lag (days)	PM_2.5 ≤ P₅₀		PM_2.5 > P₅₀		Interaction P values
Lag (days)	β (95% CI) value	P value	β (95% CI) value	P value	Interaction P values
0–9
≤ Threshold	1.096(0.556,1.636)	< 0.001	0.258(−0.218,0.733)	0.288	0.038
> Threshold	− 2.740(− 3.711,-1.769)	< 0.001	−8.162(− 11.400,-4.924)	< 0.001	0.158
10–14
≤ Threshold	0.936(0.341,1.531)	0.002	0.659(0.303,1.014)	< 0.001	0.537
> Threshold	− 2.009(− 2.698,-1.320)	< 0.001	− 5.549(− 7.527,-3.572)	< 0.001	0.734
15–59
≤ Threshold	5.128(5.128,5.128)	< 0.001	1.900(1.412,2.388)	< 0.001	< 0.001
> Threshold	−1.135(− 1.438,-0.833)	< 0.001	1.772(−0.240,3.785)	0.084	< 0.001
70–90
≤ Threshold	3.206(1.551,4.862)	< 0.001	2.561(1.793,3.329)	< 0.001	0.663
> Threshold	−0.554(− 0.939,-0.169)	0.005	−2.671(− 3.724,-1.619)	< 0.001	< 0.001
0–90
≤ Threshold	− 5.457(− 7.607,-3.306)	< 0.001	2.822(2.170,3.474)	< 0.001	0.016
> Threshold	− 0.979(−1.299,-0.659)	< 0.001	−3.559(− 6.867,-0.251)	0.035	< 0.001

The regression coefficients and 95% confidence intervals (CIs) were estimated using a generalized linear model for the relationship between mean temperature and sperm quality, adjusted for body mass index (BMI), education level, smoking status, season of semen sample, days abstaining, and relative humidity. The regression coefficients show changes in the percentage of normal sperm morphology with a 1 °C increase in mean temperature. Interaction p-values: the interactive effect of PM_2.5 and temperature on sperm quality was considered statistically significant if the interaction term p-value was less than 0.05
0–9, 10–14, 15–69, 70–90, and 0–90 represent the five exposure windows (0–9, 10–14, 15–69, 70–90, and 0–90 days before semen examination, respectively)
≤ Threshold, > Threshold: the study population was divided into ≤ Threshold and > Threshold groups by threshold values of temperature on sperm quality. The threshold values of temperature were 22.61 °C, 21.72 °C, 14.45 °C, 12.68 °C, and 14.69 °C at lag 0–9, lag 10–14, lag 15–69, lag 70–90, and lag 0–90 days for the percentage of normal sperm morphology
PM_2.5 ≤ P₅₀, PM_2.5 > P₅₀: the study population was divided into PM_2.5 ≤ P₅₀ and PM_2.5 > P₅₀ groups by the 50th percentile of PM_2.5. PM_2.5: particulate matter ≤2.5 μm in aerodynamic diameter

ISSN: 1476-069X