Temporal and Spatial Variations in the Twinning Rate in Norway
1Hanken School of Economics,Helsinki,Finland.
Summary
Twinning rates (TWR) show geographical variation, being highest in Nordic populations. In Norway, TWR varied regionally from 1916-1926, but this variation disappeared by 1960-1988, suggesting convergence.
Area of Science:
- Human genetics
- Reproductive epidemiology
- Population studies
Background:
- Twinning rate (TWR) exhibits significant global geographical variations.
- Populations of African origin generally have higher TWRs, Europeans intermediate, and Asiatic populations low.
- Within Europe, a south-to-north cline exists, with Nordic populations showing the highest TWRs.
Purpose of the Study:
- To analyze the temporal and regional variations in twinning rates (TWR) in Norway.
- To investigate spatial patterns of TWR in Norwegian counties during specific historical periods.
- To assess changes in TWR heterogeneity over time in Norway.
Main Methods:
- Analysis of twinning data in Norway from 1900 to 2014.
- Regional TWR analysis for Norwegian counties during 1916-1926 and 1960-1988.
- Application of spatial regression models, including longitude and its square, to identify TWR distribution patterns.
Main Results:
- Significant regional heterogeneity in TWR was observed in Norway during 1916-1926, with spatial variation following a west-east direction.
- Spatial models showed only slight goodness of fit for the observed heterogeneity.
- No significant regional variation in TWR was detected for the period 1960-1988.
Conclusions:
- Regional differences in twinning rates within Norway appear to have diminished over time.
- Environmental and genetic factors contributing to TWR variations may have converged across Norwegian counties.
- The study indicates a trend towards a uniform, lower twinning rate in Norway in recent decades.
Keywords:
assisted reproductive technologycountygeographical co-ordinatesmulticollinearityregression analysisMore Related Videos
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