Daily birth numbers in Passo Fundo, South Brazil, 1997-1999: trends and periodicities

• Published in: Brazilian journal of medical and biological research Vol. 35; no. 8; pp. 985 - 990
• Main Authors: Mikulecky, M, Lisboa, H R K
• Format: Journal Article
• Language: English; Portuguese
• Published: Brazil Associação Brasileira de Divulgação Científica 01.08.2002
• Subjects: BIOLOGY; Birth Rate - trends; Births; Brazil; Confidence Intervals; Cosinor; Cosmogeophysical-biomedical parallelism; Humans; Infant, Newborn; MEDICINE, RESEARCH & EXPERIMENTAL; Moon; Multiseptans; Periodicity; Periodogram; Poisson Distribution; Seasonality; Seasons; Solar and lunar cycles; South Brazil; Weekly rhythm; Brazil; Solar and lunar cycles; Multiseptans; South Brazil; Seasonality; Births; Cosmogeophysical-biomedical parallelism; Weekly rhythm; Periodogram; Cosinor
• ISSN: 0100-879X; 1414-431X; 1414-431X; 0100-879X
• DOI: 10.1590/S0100-879X2002000800017

Between October 6, 1997 and April 30, 1999, 5011 births (mean: 8.76 per day) were registered in the city of Passo Fundo, South Brazil. The sequence of 572 daily birth numbers was not random (iteration test). Neyman distribution (m = yen ) showed the best fit. Clusters of days with higher birth numbers alternated with days with low numbers of births. Periodogram analysis revealed a significant periodicity of 6.98 days. The cosinor regression, testing 10 a priori supposed period lengths, found significant seasonality peaking in August-September and significantly highest birth numbers on Thursdays. Among the lunar and solar rotation cycles, the tropic lunar cycle and its 4th harmonic were most pronounced, in agreement with results concerning natality in Germany obtained by Svante Arrhenius in the 19th century. These findings confirm Derer-Halberg's concept of multiseptans. In addition to cycling, a significantly increasing linear trend with a daily increase of 0.0045 births was encountered. This documents a growth of the population in agreement with national statistical data.