[HTML][HTML] Decline and loss of birth seasonality in Spain: analysis of 33 421 731 births over 60 years
R Cancho‐Candela, JM Andrés‐de Llano… - … of Epidemiology and …, 2007 - ncbi.nlm.nih.gov
R Cancho‐Candela, JM Andrés‐de Llano, J Ardura‐Fernández
Journal of Epidemiology and Community Health, 2007•ncbi.nlm.nih.govMethods A time series composed of 33 421 731 births in Spain in the period 1941–2000
was analysed. The series comes from the National Institute of Statistics and was processed
according to the following norms:(1) normalisation of the duration of months and years;(2)
clinical analysis of temporal series (isolation of seasonal component);(3) Fourier's spectral
analysis; and (4) cosinor analysis (adjustment to the cosine curve of two harmonics). Results
Significant seasonal rhythm was found in the set of births, both for a 12‐month period and a …
was analysed. The series comes from the National Institute of Statistics and was processed
according to the following norms:(1) normalisation of the duration of months and years;(2)
clinical analysis of temporal series (isolation of seasonal component);(3) Fourier's spectral
analysis; and (4) cosinor analysis (adjustment to the cosine curve of two harmonics). Results
Significant seasonal rhythm was found in the set of births, both for a 12‐month period and a …
Methods
A time series composed of 33 421 731 births in Spain in the period 1941–2000 was analysed. The series comes from the National Institute of Statistics and was processed according to the following norms:(1) normalisation of the duration of months and years;(2) clinical analysis of temporal series (isolation of seasonal component);(3) Fourier's spectral analysis; and (4) cosinor analysis (adjustment to the cosine curve of two harmonics).
Results
Significant seasonal rhythm was found in the set of births, both for a 12‐month period and a 6‐month period. The rhythm shows bimodal morphology, with a pronounced birth peak in April and a smaller one in September. These peaks correspond to July and December conceptions, respectively. The major birth peak shifted to March–May between the 1940s and the 1980s. Birth rhythm changed after the 1960s, with a decrease in amplitude and later loss of seasonality in the 1990s.
Conclusions
In Spain, seasonal birth rhythm shows a decline from 1970, and, finally, lack of birth seasonality in 1991–2000. This trend is similar to other European countries, although Spain shows a more intense loss of seasonality.
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