Differences in the Quality of Semen in Outdoor Workers during Summer and Winter

Levine, Richard J.; Mathew, Ravi M.; Chenault, C. Brandon; Brown, Michelle H.; Hurtt, Mark E.; Bentley, Karin S.; Mohr, Kathleen; Working, Peter K.

doi:10.1056/nejm199007053230103

Cited by 123 publications

(44 citation statements)

References 18 publications

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“…Demographers have implicated a host of social, environmental and physiological factors that may interact to drive birth seasonality. While a consensus has yet to be reached, and mechanisms vary geographically, hypothesized drivers include income, culture, race, holidays, rainfall, cold winters and seasonally variable sperm quality [38,[50][51][52][53][54][55][56]. Although we focused on characterizing the variation in birth seasonality, rather than the mechanisms underlying this variation, it is our hope that the latitudinal gradient in peak birth timing and amplitude observed here will help elucidate the primary drivers of birth seasonality.…”

Section: Discussionmentioning

confidence: 99%

Human birth seasonality: latitudinal gradient and interplay with childhood disease dynamics

et al. 2014

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More than a century of ecological studies have demonstrated the importance of demography in shaping spatial and temporal variation in population dynamics. Surprisingly, the impact of seasonal recruitment on infectious disease systems has received much less attention. Here, we present data encompassing 78 years of monthly natality in the USA, and reveal pronounced seasonality in birth rates, with geographical and temporal variation in both the peak birth timing and amplitude. The timing of annual birth pulses followed a latitudinal gradient, with northern states exhibiting spring/summer peaks and southern states exhibiting autumn peaks, a pattern we also observed throughout the Northern Hemisphere. Additionally, the amplitude of United States birth seasonality was more than twofold greater in southern states versus those in the north. Next, we examined the dynamical impact of birth seasonality on childhood disease incidence, using a mechanistic model of measles. Birth seasonality was found to have the potential to alter the magnitude and periodicity of epidemics, with the effect dependent on both birth peak timing and amplitude. In a simulation study, we fitted an susceptible-exposed-infectedrecovered model to simulated data, and demonstrated that ignoring birth seasonality can bias the estimation of critical epidemiological parameters. Finally, we carried out statistical inference using historical measles incidence data from New York City. Our analyses did not identify the predicted systematic biases in parameter estimates. This may be owing to the well-known frequency-locking between measles epidemics and seasonal transmission rates, or may arise from substantial uncertainty in multiple model parameters and estimation stochasticity.

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Section: Discussionmentioning

confidence: 99%

Human birth seasonality: latitudinal gradient and interplay with childhood disease dynamics

et al. 2014

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“…Of the 1,346 subjects included in our semen quality study during the period from June to December 2007, we only included those who participated during the winter (i.e., December) in the present study ( n = 232), because the winter weather may have a slight influence on sperm quality (Carlsen et al 2004; Chen et al 2003; Levine et al 1990) and the level of PAH pollution is relatively heavy and stable during this time [Chongqing Environmental Protection Bureau (CEPB) 2007]. There were no statistical differences between the subjects included in this study and the rest of the study population with regard to demographic characteristics and socioeconomic status.…”

Section: Methodsmentioning

confidence: 99%

Association between Urinary Polycyclic Aromatic Hydrocarbon Metabolites and Sperm DNA Damage: A Population Study in Chongqing, China

Han

Zhou²,

Cui³

et al. 2011

Environ Health Perspect

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BackgroundPolycyclic aromatic hydrocarbons (PAHs), a class of the most ubiquitous environmental contaminants, may reduce male reproductive functions, but the data from human population studies are very limited.ObjectivesWe designed this study to determine whether environmental exposure to PAHs contributes to the alteration in semen quality, sperm DNA damage, and apoptosis in the general male human population.MethodsWe measured urinary levels of four PAH metabolites and assessed semen quality, sperm apoptotic markers with Annexin V assay, and sperm DNA damage with comet assay in 232 men from Chongqing, China.ResultsWe found that increased urinary 2-hydroxynaphthalene (2-OHNa) levels were associated with increased comet parameters, including the percentage of DNA in the tail (tail%) [β coefficient = 13.26% per log unit 2-OHNa (micrograms per gram creatinine); 95% confidence interval (CI), 7.97–18.55]; tail length (12.25; 95% CI, 0.01–24.52), and tail distribution (7.55; 95% CI, 1.28–18.83). The urinary level of 1-hydroxypyrene was associated only with increased tail% (5.32; 95% CI, 0.47–10.17). Additionally, the increased levels of four urinary PAH metabolites were significantly associated with decreased vital Annexin V negative sperm counts. However, there was no significant association between urinary PAH metabolite levels and human semen parameters or morphology of the sperm samples.ConclusionsOur data indicate that the environmental level of PAH exposure is associated with increased sperm DNA damage but not with semen quality. These findings suggest that exposure to PAHs may disrupt sperm DNA and thereby interfere with human male fertility.

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“…We chose the > 90°F cutoff arbitrarily to facilitate comparison with the results of Sokol et al (2006). Several studies have suggested that testicular function is influenced by season (Gyllenborg et al 1999; Levine et al 1988, 1990, 1992); this may account at least in part for the reduction in spring births in regions with warm climates, although it is unclear if this effect is related entirely to temperature or if there may be some other seasonal component, such as photoperiod, that leads to this phenomenon. The air pollution exposure metric was entered into the models as a continuous variable, and the β–coefficients are presented for a 15–ppb increase in O 3 and a 10–μg/m 3 increase in PM 2.5 .…”

Section: Methodsmentioning

confidence: 99%

The Effect of Ambient Air Pollution on Sperm Quality

Hansen

Luben

Sacks

et al. 2010

Environ Health Perspect

134

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BackgroundResearch has suggested an association with ambient air pollution and sperm quality.ObjectivesWe investigated the effect of exposure to ozone (O3) and particulate matter < 2.5 μm in aerodynamic diameter (PM2.5) on sperm quality.MethodsWe reexamined a previous cohort study of water disinfection by-products to evaluate sperm quality in 228 presumed fertile men with different air pollution profiles. Outcomes included sperm concentration, total sperm per ejaculate (count), and morphology, as well as DNA integrity and chromatin maturity. Exposures to O3 and PM2.5 were evaluated for the 90–day period before sampling. We used multivariable linear regression, which included different levels of adjustment (i.e., without and with season and temperature) to assess the relationship between exposure to air pollutants during key periods of sperm development and adverse sperm outcomes.ResultsSperm concentration and count were not associated with exposure to PM2.5, but there was evidence of an association (but not statistically significant) with O3 concentration and decreased sperm concentration and count. Additionally, a significant increase in the percentage of sperm cells with cytoplasmic drop [β = 2.64; 95% confidence interval (CI), 0.21–5.06] and abnormal head (β = 0.47; 95% CI, 0.03–0.92) was associated with PM2.5 concentration in the base model. However, these associations, along with all other sperm outcomes, were not significantly associated with either pollutant after controlling for season and temperature. Overall, although we found both protective and adverse effects, there was generally no consistent pattern of increased abnormal sperm quality with elevated exposure to O3 or PM2.5.ConclusionsExposures to O3 or PM2.5 at levels below the current National Ambient Air Quality Standards were not associated with statistically significant decrements in sperm outcomes in this cohort of fertile men. However, some results suggested effects on sperm concentration, count, and morphology.

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Differences in the Quality of Semen in Outdoor Workers during Summer and Winter

Abstract: Semen quality deteriorates during the summer. This phenomenon may account at least in part for the reduction in the birth rate during the spring in regions with warm climates.

Cited by 123 publications

References 18 publications

Human birth seasonality: latitudinal gradient and interplay with childhood disease dynamics

Human birth seasonality: latitudinal gradient and interplay with childhood disease dynamics

Association between Urinary Polycyclic Aromatic Hydrocarbon Metabolites and Sperm DNA Damage: A Population Study in Chongqing, China

The Effect of Ambient Air Pollution on Sperm Quality

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