Seasonal Sunshine and Vitamin D: A Possible Explanation for Differences in European and United States Birth Patterns

Abstract

This study tests whether seasonal differences in the United States and European sunshine is associated with human birth patterns. Birth data are adjusted for 31-day months, leap years, and an annual percentage. Clear observations and birth indices are correlated for European and U.S. cities. With 2-month exposure to clearness, r-values are Chicago (0.63), Bismarck (0.81), Dallas (0.86), Thessaloniki (0.66), and Copenhagen (0.54) and, with 3-month exposure, Amsterdam (0.69). Peak clearness occurs during the autumn for the United States and spring/summer for Europe. Differences in clearness may explain birth pattern differences and reduced U.S. births in the 1930s. Although the effect of vitamin D is plausible, further research is required.

The following data sources are acknowledged for their assistance:

Illinois Department of Public Health (http://www.idph.state.il.us/health/statshome.htm) for Chicago birth data.

North Dakota Department of Health (http://www.ndhealth.gov/vital/stats.htm) for North Dakota births.

Texas Dept of State Health Services (http://www.dshs.state.tx.us/datareports.shtm) for Dallas birth data.

National Statistical Service of Greece ([email protected]) for Thessaloniki birth data

Statistics Denmark (http://www.statbank.dk/statbank5a/default.asp?w=1680) for Copenhagen birth data.

American Journal of Human Biology for permission to use Dallas birth and seasonality data from “Human Birth Seasonality and Sunshine,” Cummings DR, Epub Oct. 2009.

Central Bureau of Statistics (http://www.cbs.an/) for birth data for the Netherlands

U. S. Climatic Data Center for diskette and on-line world-wide cloud data

For clear day data for Bismarck, ND and 17 Texas cities, go to: http://www.ncdc.noaa.gov/oa/ncdc.html. Select “Free data”. Select “Free data G. Select under “data tables”… Cloudiness-mean number of days (clear-partly cloud-cloudy).