, based on data from a 5.5-year population-based study in Korea.
In a model adjusted for age, sex, smoking, alcohol consumption, regular exercise, and income status the group with high variability for all four parameters had a significantly higher risk for all-cause mortality (hazard ratio, 2.27; 95% confidence interval, 2.13-2.42), for MI (HR, 1.43; 95% CI, 1.25-1.64), and for stroke (HR, 1.41; 95% CI, 1.25-1.60), compared with the group with low variability for all four parameters. The association with risk was graded and persisted after multivariable adjustment.
“Variability in metabolic parameters may be prognostic surrogate markers for predicting mortality and cardiovascular outcomes,” wrote senior author Seung-Hwan Lee, MD, PhD, and professor of endocrinology at the College of Medicine of the Catholic University of Korea in Seoul, South Korea, and colleagues. “High variability in metabolic parameters (may be) associated with adverse health outcomes not only in a diseased population, but also in the relatively healthy population although the mechanism could be somewhat different.”
Korea has a single-payer system, the Korean National Health Insurance system, that includes health information on its entire population. The researchers selected data from 6,748,773 people who were free of diabetes mellitus, hypertension, and dyslipidemia, and who underwent three or more health examinations during 2005-2012 that documented body mass index (BMI), fasting blood glucose, systolic blood pressure, and total cholesterol. Participants were followed to the end of 2015, for a median follow-up of 5.5 years. There were 54,785 deaths (0.8%), 22,498 cases of stroke (0.3%), and 21,452 MIs (0.3%).
The research team defined high variability as the highest quartile, classifying participants according to the number of high-variability parameters. A score of 4 indicated high variability in all four metabolic parameters – body weight, systolic blood pressure, total cholesterol, and fasting blood glucose.
In the highest quartile in fasting blood glucose variability, compared with the lowest quartile, the risk of all-cause mortality increased by 20% (HR, 1.20; 95% CI, 1.18-1.23), MI by 16% (HR, 1.16; 95% CI, 1.12-1.21), and stroke by 13% (HR, 1.13; 95% CI, 1.09-1.17).
For the highest quartile in total cholesterol variability, compared with the lowest quartile, the risk of all-cause mortality increased by 31% (HR, 1.31; 95% CI, 1.28-1.34), MI by 10% (HR, 1.10; 95% CI, 1.06-1.14), and stroke by 6% (HR, 1.06; 95% CI, 1.03-1.10).
For the highest quartile in systolic BP variability, compared with the lowest quartile, the risk of all-cause mortality increased by 19% (HR, 1.19; 95% CI, 1.16-1.22), MI by 7% (HR, 1.07; 95% CI, 1.03-1.11), and stroke by 14% (HR, 1.14; 95% CI, 1.10-1.18).
For the highest quartile in BMI variability, compared with the lowest quartile, the risk of all-cause mortality increased by 53% (HR, 1.53; 95% CI, 1.50-1.57), MI by 14% (HR, 1.14; 95% CI, 1.09-1.18), and stroke by 14% (HR, 1.14; 95% CI, 1.10-1.18).
“It is not certain whether these results from Korea would apply to the United States. However, several previous studies on variability were performed in other populations, suggesting that it is likely to be a common phenomenon,” the authors wrote.
The study was supported in part by the National Research Foundation of Korea Grant funded by the Korean Government. The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
SOURCE: Lee S-H et al. Circulation. 2018 Oct.