Publications (2)8.95 Total impact
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Article: Exogenous shocks to the human sex ratio: the case of September 11, 2001 in New York City.
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ABSTRACT: The human secondary sex ratio reportedly falls in populations subjected to exogenous stressors such as earthquakes or political and social upheavals. Explanations of the association include reduced conception of males and increased fetal deaths among males. The latter explanation has been supported by research reporting that the sex ratio in California fell 3 months, but not 8, 9 or 10 months, after the terrorist attacks of September 11, 2001. California's distance from the attacks raises the questions of whether the results arose from chance and would be found elsewhere. We contribute to the literature by testing the association between the secondary sex ratio and the events of September 11 in New York City. We replicate the California tests by applying interrupted time-series methods, which control for secular trends, seasonality and other forms of autocorrelation, to 91 cohorts born in New York City during 28-day periods from January 1996 to June 2002. As hypothesized, the sex ratio in New York City in the period 1 January to 28 January 2002 fell to 1, which was the lowest observed value during the test period and significantly (i.e. P < 0.01, two-tailed test) below the value expected from history. Our findings support the male fetal loss explanation of the association between exogenous population shocks and the secondary sex ratio.Human Reproduction 01/2007; 21(12):3127-31. · 4.47 Impact Factor -
Article: Antioxidant intake is associated with semen quality in healthy men.
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ABSTRACT: We seek to determine whether dietary and supplement intake of specific micronutrients (zinc and folate) and antioxidants (vitamins C, E and beta-carotene) is associated with semen quality. Ninety-seven healthy, non-smoking men provided semen and were interviewed. Average daily nutrient intake from food and supplements was derived from a self-administered food frequency questionnaire. Intake levels were summarized as low, moderate and high. Semen volume, sperm concentration, total sperm count, motility, progressive motility and total progressively motile sperm count (TPMS) were measured. After controlling for covariates, a high intake of antioxidants was associated with better semen quality but, in almost all cases, there was no clear dose relationship in that moderate intake groups had the poorest semen quality. For example, positive associations were observed between vitamin C intake and sperm number as reflected in the higher mean count (P=0.04), concentration (P=0.05) and TPMS (P = 0.09); between vitamin E intake and progressive motility (P = 0.04) and TPMS (P = 0.05); and between beta-carotene intake and sperm concentration (P = 0.06) and progressive motility (P = 0.06). Folate and zinc intake were not associated with improved semen quality. In a convenience sample of healthy non-smoking men from a non-clinical setting, higher antioxidant intake was associated with higher sperm numbers and motility.Human Reproduction 05/2005; 20(4):1006-12. · 4.47 Impact Factor
