A large decrease in the magnitude of seasonal fluctuations in mortality among elderly explains part of the increase in longevity in Sweden during 20th century.
Cohort
Longevity
Mortality
Seasonal fluctuations
Winter excess mortality
Journal
BMC public health
ISSN: 1471-2458
Titre abrégé: BMC Public Health
Pays: England
ID NLM: 100968562
Informations de publication
Date de publication:
09 Nov 2020
09 Nov 2020
Historique:
received:
03
07
2020
accepted:
22
10
2020
entrez:
10
11
2020
pubmed:
11
11
2020
medline:
15
5
2021
Statut:
epublish
Résumé
Mortality rates are known to depend on the seasons and, in temperate climates, rates are highest during winter. The magnitude of these seasonal fluctuations in mortality has decreased substantially in many countries during the 20th century, but the extent to which this decrease has contributed to the concurrent increase in life expectancy is not known. Here, I describe how the seasonality of all-cause mortality among people ages 60 years or more has changed in Sweden between 1860 and 1995, and investigate how this change has contributed to the increase in life expectancy observed during the same time period. Yearly sex-specific birth cohorts consisting of all people born in Sweden between 1800 and 1901 who reached at least 59 years of age were obtained from a genealogical database. The mortality rates for each cohort were modeled by an exponential function of age modulated by a sinusoidal function of time of year. The potential impact of seasonal fluctuations on life expectancy was investigated by a novel decomposition of the total mortality rate into a seasonal part and a part independent of the seasons. Cohort life expectancy at age 60 was used to quantify changes in lifespan during the time period. The magnitude of seasonal fluctuations in mortality rates decreased substantially between 1860 and 1995. For cohorts born in 1800, the risk of dying during the winter season was almost twice that of dying during summer. For cohorts born in 1900, the relative increase in winter mortality was 10%. Cohort life expectancy at age 60 increased by 4.3 years for men and 6.8 years for women, and the decrease in seasonal mortality fluctuations accounted for approximately 40% of this increase in average lifespan. By following a large number of extinct cohorts, it was possible to show how the decrease in seasonal fluctuations in mortality has contributed to an increase in life expectancy. The decomposition of total mortality introduced here might be useful to better understand the processes and mechanisms underlying the marked improvements in life expectancy seen over the last 150 years.
Sections du résumé
BACKGROUND
BACKGROUND
Mortality rates are known to depend on the seasons and, in temperate climates, rates are highest during winter. The magnitude of these seasonal fluctuations in mortality has decreased substantially in many countries during the 20th century, but the extent to which this decrease has contributed to the concurrent increase in life expectancy is not known. Here, I describe how the seasonality of all-cause mortality among people ages 60 years or more has changed in Sweden between 1860 and 1995, and investigate how this change has contributed to the increase in life expectancy observed during the same time period.
METHODS
METHODS
Yearly sex-specific birth cohorts consisting of all people born in Sweden between 1800 and 1901 who reached at least 59 years of age were obtained from a genealogical database. The mortality rates for each cohort were modeled by an exponential function of age modulated by a sinusoidal function of time of year. The potential impact of seasonal fluctuations on life expectancy was investigated by a novel decomposition of the total mortality rate into a seasonal part and a part independent of the seasons. Cohort life expectancy at age 60 was used to quantify changes in lifespan during the time period.
RESULTS
RESULTS
The magnitude of seasonal fluctuations in mortality rates decreased substantially between 1860 and 1995. For cohorts born in 1800, the risk of dying during the winter season was almost twice that of dying during summer. For cohorts born in 1900, the relative increase in winter mortality was 10%. Cohort life expectancy at age 60 increased by 4.3 years for men and 6.8 years for women, and the decrease in seasonal mortality fluctuations accounted for approximately 40% of this increase in average lifespan.
CONCLUSION
CONCLUSIONS
By following a large number of extinct cohorts, it was possible to show how the decrease in seasonal fluctuations in mortality has contributed to an increase in life expectancy. The decomposition of total mortality introduced here might be useful to better understand the processes and mechanisms underlying the marked improvements in life expectancy seen over the last 150 years.
Identifiants
pubmed: 33167913
doi: 10.1186/s12889-020-09749-4
pii: 10.1186/s12889-020-09749-4
pmc: PMC7654045
doi:
Types de publication
Journal Article
Langues
eng
Sous-ensembles de citation
IM
Pagination
1674Références
Am J Epidemiol. 1993 Feb 1;137(3):331-41
pubmed: 8452141
Ann Demogr Hist (Paris). 1983;:208-30
pubmed: 11629196
Philos Trans R Soc Lond B Biol Sci. 2015 Apr 19;370(1666):
pubmed: 25750242
Int J Biometeorol. 1989 Jun;33(2):71-6
pubmed: 2759722
Am J Epidemiol. 2004 Sep 1;160(5):492-502
pubmed: 15321847
Lancet Infect Dis. 2007 Oct;7(10):658-66
pubmed: 17897608
Am J Epidemiol. 2002 Jan 1;155(1):80-7
pubmed: 11772788
Epidemiology. 2009 Mar;20(2):205-13
pubmed: 19194300
PLoS One. 2020 Jun 4;15(6):e0233384
pubmed: 32497107
Am J Epidemiol. 1976 Jun;103(6):565-75
pubmed: 937340
Demography. 1997 Feb;34(1):1-15
pubmed: 9074828
Lancet. 1970 Feb 7;1(7641):291-6
pubmed: 4189306
Int J Epidemiol. 2005 Oct;34(5):1149-59
pubmed: 15964911
Scand J Hist. 2001;26(3):157-76
pubmed: 17844640
J Epidemiol Community Health. 2003 Oct;57(10):784-9
pubmed: 14573581
JAMA. 1997 Sep 24;278(12):1012-4
pubmed: 9307350
Lancet Infect Dis. 2012 Jan;12(1):36-44
pubmed: 22032844
Int J Epidemiol. 1991 Dec;20(4):971-7
pubmed: 1800438
Milbank Mem Fund Q. 1971 Oct;49(4):509-38
pubmed: 5155251
Scand J Soc Med Suppl. 1981;21:1-101
pubmed: 7022620
Eur J Public Health. 2015 Apr;25(2):339-45
pubmed: 24919695
BMC Public Health. 2007 Sep 24;7:263
pubmed: 17892590
Int J Circumpolar Health. 2002 Nov;61(4):292-9
pubmed: 12546188
Elife. 2018 Oct 30;7:
pubmed: 30373715
Int J Epidemiol. 2001 Oct;30(5):1109-16
pubmed: 11689530
Int J Biometeorol. 1998 Dec;42(2):84-8
pubmed: 9923200