In an analysis that included nearly 1.2 million participants and more than 135,000 deaths, mortality associated with a history of diabetes, stroke, or heart attack was similar for each condition, and the risk of death increased substantially with each additional condition a patient had, according to a study in the July 7 issue of JAMA.
The prevalence of cardiometabolic multimorbidity (defined in this study as a history of 2 or more of the following: diabetes mellitus, stroke, myocardial infarction [MI; heart attack]) is increasing rapidly. Considerable evidence exists about the mortality risk of having any 1 of these conditions alone. However, evidence is sparse about life expectancy among people who have 2 or 3 cardiometabolic conditions at the same time, according to background information in the article.
John Danesh, F.Med.Sci., of the University of Cambridge, England, and colleagues estimated reductions in life expectancy associated with cardiometabolic multimorbidity. Age- and sex-adjusted mortality rates and hazard ratios (HR) were calculated using individual participant data from the Emerging Risk Factors Collaboration (689,300 participants; 91 cohorts; years of baseline surveys: 1960-2007; latest mortality follow-up: April 2013; 128,843 deaths). The hazard ratios from this study population were compared with those from the UK Biobank (499,808 participants; years of baseline surveys: 2006-2010; latest mortality follow-up: November 2013; 7,995 deaths).
Among the primary findings:
• Compared to participants who did not have a history of any of these conditions (diabetes mellitus, stroke, heart attack), participants who had 1 condition had about twice the rate of death; 2 conditions, about 4 times the rate of death; and all 3 conditions, about 8 times the rate of death. "Our results emphasize the importance of measures to prevent cardiovascular disease in people who already have diabetes, and, conversely, to avert diabetes in people who already have cardiovascular disease," the authors write.
• The results suggest that estimated reductions in life expectancy associated with cardiometabolic multimorbidity are of similar magnitude to those previously noted for exposures of major concern to public health, such as lifelong smoking (10 years of reduced life expectancy) and infection with the human immunodeficiency virus (11 years of reduced life expectancy). For example, at the age of 60 years, a history of any 2 of these conditions was associated with 12 years of reduced life expectancy and a history of all 3 of these conditions was associated with 15 years of reduced life expectancy. The researchers estimated even greater reductions in life expectancy in patients with multimorbidity at younger ages, such as 23 years of life lost in patients with 3 conditions at the age of 40 years.
• Modification by sex of associations between cardiometabolic multimorbidity and mortality were noted. For men, the association between baseline cardiovascular disease (i.e., a history of stroke or MI) and reduced survival was stronger than for women, whereas the association between baseline diabetes and reduced survival was stronger for women. Consequently, about 60 percent of the years of life lost from cardiometabolic multimorbidity can be attributed to cardiovascular deaths for men compared with only about 45 percent for women. "Nevertheless, for both men and women, our findings indicate that associations of cardiometabolic multimorbidity extend beyond cardiovascular mortality. Future work will seek to elucidate explanations for these interactions by sex."
The authors write that their results highlight the need to balance the primary prevention and secondary prevention of cardiovascular disease. "About 1 percent of the participants in the cohorts we studied had cardiometabolic multimorbidity compared with an estimate of 3 percent from recent surveys in the United States. There are currently an estimated 10 million adults in the United States and the European Union with cardiometabolic multimorbidity. Nevertheless, an overemphasis on the substantial reductions in life expectancy estimated for the subpopulation with multimorbidity could divert attention and resources away from population-wide strategies that aim to improve health for the large majority of the population."