Fluctuations in weight, blood pressure, cholesterol and/or blood sugar levels in otherwise healthy people may be associated with a higher risk of heart attack, stroke and death from any cause compared to people with more stable readings, according to research. This is the first study to suggest that high variability of these risk factors has a negative impact on relatively healthy people. The study is also the first to indicate that having multiple measures with high variability adds to the risk.
Compared to people who had stable measurements during an average 5.5 year follow-up period, those with the highest amount of variability (in the upper 25%) on all measurements were: 127% more likely to die; 43% more likely to have a heart attack; and 41% more likely to have a stroke.
Using data from the Korean National Health Insurance system, researchers examined data on 6,748,773 people who had no previous heart attacks and were free of diabetes, high blood pressure, or high cholesterol at the beginning of the study. All participants had at least three health examinations between 2005 and 2012 (every two years is recommended in the system). Records of the exams documented body weight, fasting blood sugar, systolic (top number) blood pressure and total cholesterol.
Because high variability could result from either positive or negative changes, the researchers looked separately at the effect of variability in participants who were more than 5% improved or worsened on each measurement. In both the improved and the worsened groups, high variability was associated with a significantly higher risk of death.
"Healthcare providers should pay attention to the variability in measurements of a patient's blood pressure, cholesterol and glucose levels as well as body weight. Trying to stabilise these measurements may be an important step in helping them improve their health," said Dr Seung-Hwan Lee, senior author of the study and professor of endocrinology at the College of Medicine of the Catholic University of Korea in Seoul, South Korea.
The study was observational, which means that it cannot prove a cause-and-effect relationship between high variability and the risk of heart attacks, strokes or death from any cause. The study also did not delve into the reasons behind the fluctuations in the participants' risk factor measurements.
"It is not certain whether these results from Korea would apply to the US. However, several previous studies on variability were performed in other populations, suggesting that it is likely to be a common phenomenon," Lee said.
Background: Variability in metabolic parameters, such as fasting blood glucose and cholesterol concentrations, blood pressure, and body weight can affect health outcomes. We investigated whether variability in these metabolic parameters has additive effects on the risk of mortality and cardiovascular outcomes in the general population.
Methods: Using nationally representative data from the Korean National Health Insurance System, 6748773 people who were free of diabetes mellitus, hypertension, and dyslipidemia and who underwent ≥3 health examinations from 2005 to 2012 were followed to the end of 2015. Variability in fasting blood glucose and total cholesterol concentrations, systolic blood pressure, and body mass index was measured using the coefficient of variation, SD, variability independent of the mean, and average real variability. High variability was defined as the highest quartile of variability. Participants were classified numerically according to the number of high-variability parameters (eg, a score of 4 indicated high variability in all 4 metabolic parameters). Cox proportional hazards models adjusting for age, sex, smoking, alcohol, regular exercise, income, and baseline levels of fasting blood glucose, systolic blood pressure, total cholesterol, and body mass index were used.
Results: There were 54785 deaths (0.8%), 22498 cases of stroke (0.3%), and 21452 myocardial infarctions (0.3%) during a median follow-up of 5.5 years. High variability in each metabolic parameter was associated with a higher risk for all-cause mortality, myocardial infarction, and stroke. Furthermore, the risk of outcomes increased significantly with the number of high-variability metabolic parameters. In the multivariable-adjusted model comparing a score of 0 versus 4, the hazard ratios (95% CIs) were 2.27 (2.13-2.42) for all-cause mortality, 1.43 (1.25-1.64) for myocardial infarction, and 1.41 (1.25-1.60) for stroke. Similar results were obtained when modeling the variability using the SD, variability independent of the mean, and average real variability, and in various sensitivity analyses.
Conclusions: High variability of fasting blood glucose and total cholesterol levels, systolic blood pressure, and body mass index was an independent predictor of mortality and cardiovascular events. There was a graded association between the number of high-variability parameters and cardiovascular outcomes.
Mee Kyoung Kim, Kyungdo Han, Yong-Moon Park, Hyuk-Sang Kwon, Gunseog Kang, Kun-Ho Yoon, Seung-Hwan Lee
[link url="https://www.heart.org/en/news/2018/10/01/big-fluctuations-in-bp-and-cholesterol-increase-heart-disease-stroke-risk"]American Heart Association material[/link]
[link url="https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.118.034978"]Circulation abstract[/link]