A large nationwide Danish cohort study found associations between long-term exposure to road traffic noise and air pollution and increased risk of infertility diagnoses. Potential biological mechanisms included direct toxic effects of particles on sperm cells during spermatogenesis for men, and stress and sleep disturbance induced by noise exposure for women.
The research, published in The BMJ, analyzed data from 526,056 men and 377,850 women aged 30-45 years who were cohabiting or married, had fewer than 2 children, and lived in Denmark between 2000 and 2017.
Key Findings
- PM2.5 exposure was associated with a higher risk of infertility in men across the full age range (30-45 years). For each 2.9 μg/m3 increase in 5-year mean PM2.5 exposure:
- 24% higher infertility risk in men aged 30-36.9 years
- 24% higher risk in men aged 37-45 years
- Road traffic noise exposure was associated with infertility in women aged 35-45 years, but not in younger women (30-34.9 years). For each 10 dB increase in 5-year mean road traffic noise exposure:
- 14% increased risk of infertility in women aged 35-45 years
- No significant associations were found between PM2.5 exposure and infertility in women.
- A weak association was observed between noise exposure and infertility in men aged 37-45 years.
Methods
Researchers utilized Denmark's comprehensive national registers to identify participants who resided in Denmark between 2000-2017. Subjects were followed until infertility diagnosis, death, emigration, or end of 2017.
Exposure to road traffic noise (Lden) was estimated using the Nordic prediction method. PM2.5 concentrations were modeled using a system combining regional, urban background, and local street pollution models.
Infertility diagnoses were obtained from the Danish National Patient Register. Cox proportional hazards models were used to calculate hazard ratios, adjusting for sociodemographic variables and mutual exposure to noise and PM2.5.
Results
The study found linear exposure-response relationships for PM2.5 and male infertility, starting from around ≥ 8.5 μg/m3. For noise and female infertility (35-45 years), a close to linear exposure-response relationship was observed, leveling off at high exposures (> 65 dB).
Subgroup analyses revealed consistent associations across areas of low, median, and high population density; low, median, and high individual level education; and fourths of personal income. For women, noise-related infertility risk was confined to those without children (primary infertility).
The study had several strengths, including its large sample size, detailed residential history and exposure data, and ability to adjust for key socioeconomic variables. Limitations included lack of data on lifestyle factors and workplace exposures.
The authors declared having no competing interests.