Open Access Research article

Similar decline in mortality rate of older persons with and without type 2 diabetes between 1993 and 2004 the Icelandic population-based Reykjavik and AGES-Reykjavik cohort studies

Elin Olafsdottir12, Thor Aspelund13, Gunnar Sigurdsson34, Rafn Benediktsson34, Bolli Thorsson1, Tamara B Harris5, Lenore J Launer5, Gudny Eiriksdottir1 and Vilmundur Gudnason13*

Author Affiliations

1 Icelandic Heart Association Research Institute, Kopavogur, Iceland

2 Public Health Sciences, University of Iceland, Reykjavik, Iceland

3 Faculty of Medicine, University of Iceland, Reykjavik, Iceland

4 Landspitali University Hospital, Reykjavik, Iceland

5 Intramural Research Program, National Institute on Aging, Bethesda, MD, USA

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BMC Public Health 2013, 13:36  doi:10.1186/1471-2458-13-36

Published: 15 January 2013

Abstract

Background

A decline in mortality rates due to cardiovascular diseases and all-cause mortality has led to increased life expectancy in the Western world in recent decades. At the same time, the prevalence of type 2 diabetes, a disease associated with a twofold excess risk of cardiovascular disease and mortality, has been increasing. The objective of this study was to estimate the secular trend of cardiovascular and all-cause mortality rates in two population-based cohorts of older persons, with and without type 2 diabetes, examined 11 years apart.

Methods

1506 participants (42% men) from the population-based Reykjavik Study, examined during 1991–1996 (median 1993), mean age 75.0 years, and 4814 participants (43% men) from the AGES-Reykjavik Study, examined during 2002–2006 (median 2004), mean age 77.2 years, age range in both cohorts 70–87 years. The main outcome measures were age-specific mortality rates due to cardiovascular disease and all causes, over two consecutive 5.7- and 5.3-year follow-up periods.

Results

A 32% decline in cardiovascular mortality rate and a 19% decline in all-cause mortality rate were observed between 1993 and 2004. The decline was greater in those with type 2 diabetes, as illustrated by the decline in the adjusted hazard ratio of cardiovascular mortality in individuals with diabetes compared to those without diabetes, from 1.88 (95% CI 1.24-2.85) in 1993 to 1.46 (95% CI 1.11-1.91) in 2004. We also observed a concurrent decrease in major cardiovascular risk factors in both those with and without diabetes. A higher proportion of persons with diabetes received glucose-lowering, hypertensive and lipid-lowering medication in 2004.

Conclusions

A decline in cardiovascular and all-cause mortality rates was observed in older persons during the period 1993–2004, in both those with and without type 2 diabetes. This decline may be partly explained by improvements in cardiovascular risk factors and medical treatment over the period studied. However, type 2 diabetes still persists as an independent risk factor for cardiovascular mortality.

Keywords:
Cohort study; Type 2 diabetes; Older persons; Cardiovascular disease mortality; Reykjavik study; AGES-Reykjavik