Cardiovascular disease (CVD) claimed about 18 million lives in 2019. While obesity is traditionally associated with CVD, the extent to which this association is mediated by other health conditions linked to obesity remains unknown.
A new study recently published in the International Journal of Obesity explores how obesity contributes to CVD by investigating this association in low-risk people.
Study: Association of obesity with cardiovascular disease in the absence of traditional risk factors. Image Credit: BELLA KA PANG / Shutterstock.com
Risk factors for CVD
Traditional risk factors for CVD include an abnormal lipid profile, hypertension, diabetes, and smoking; however, people without any of these risk factors may still develop CVD at a higher rate than expected.
Body mass index (BMI) and waist-height ratio (WHtR) are measures of obesity, both of which are associated with a higher risk of CVD. WHtR is a reliable measure of abdominal obesity and correlates better with CVD risk than waist circumference or waist-hip ratio. Despite this, conflicting findings from earlier studies have made it difficult to identify definitive associations between these measurements and CVD.
Earlier research has also largely focused on obesity with traditional CVD risk factors, thus providing little clarity on whether obesity by itself is a predictor of CVD. Such clarity is required to shape prevention strategies at the population level for low-risk obese individuals.
What did the study show?
In the current study, researchers used both BMI and WHtR to evaluate how overall and abdominal obesity correlate with CVD risk in the absence of other risk factors
The study was based on a population-based cohort from the Kailuan study. This study included about 32,000 people, about two-thirds of whom were male, with a mean age of 48 years. All study participants were followed up for a median of 13 years.
The mean BMI was 24 and mean WHtR 0.51. Older people, especially males, were more likely to be overweight or obese, have less education, and more risk factors.
During this period, there were about 1,300 CVD cases. When classified by BMI into obese and normal-weight groups, the risk of CVD, particularly for stroke and myocardial infarction (MI), increased by 30%, 20%, and 60%, respectively, in the obese group.
There were about 2.2 CVD events for every 1,000 person-years in the low-BMI group as compared to about four in the obese group. After compensating for confounding factors, the risk of CVD increased by 30% in the obese group as compared to the normal BMI group.
For stroke, the risk was 20% higher in obese individuals. Comparatively, for MI, the risk increased by over 60% in obese individuals as compared to those with a normal BMI. In all cases, the risk increased linearly with the BMI.
When categorized into obese and non-obese individuals by WHtR, a similar increase in risk was observed for CVD, stroke, and MI by 25%, 20%, and 60%, respectively in obese individuals as compared to non-obese groups. With about 2.3 CVD events for every 1,000 person-years in the non-obese group, there was a linear increase to 4.1 in the obese group, with the risk being 25% higher in obese individuals.
WHtR increased with age. The strongest correlation of WHtR with CVD was observed in people under 60 years of age, who were at a 44% higher CVD risk and 37% higher risk for stroke.
What are the implications?
Our study suggests that BMI and WHtR are important influencing factors of CVD even in individuals without traditional risk factors.”
These findings corroborate earlier studies, in which BMI was found to be an independent predictor of CVD risk. Some discrepancies such as a non-linear relationship between WHtR and CVD risk, with a steep rise in risk after a WHtR threshold of 0.5, might be due to the small sample sizes in many prior studies.
It has been suggested that cardiac failure with preserved ejection fraction (CFPEF) may be caused by obesity, with a risk of myocardial fibrosis. The chronic inflammation in abdominal fat deposits associated with obesity causes changes in the secretion of multiple adipokines and cytokines. This may contribute to cardiovascular stiffness, vasodilation, and cardiac diastolic dysfunction.
Another mechanism of heightened CVD risk in obesity is the activation of the renin-angiotensin-aldosterone system (RAAS). RAAS is pro-inflammatory under disease conditions and may lead to structural remodeling and, as a result, cardiovascular injury.
The study findings emphasize the importance of controlling BMI and WHtR to prevent the development of CVD, even in individuals without traditional CVD risk factors. Given that the participants were from a coal-mining industry, which increases their risk of exposure to air pollution and stress, further research into the impact of these factors, as well as the role of dietary and physical activity patterns, is needed to ensure the generalizability of these findings.
- Luo, H., Liu, Y., Tian, X., et al. (2023). Association of obesity with cardiovascular disease in the absence of traditional risk factors. International Journal of Obesity. doi:10.1038/s41366-023-01408-z.