Published: Oct 8, 2014
By Salynn Boyles, Contributing Writer, MedPage Today

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Action Points

• Higher values of BMI and systolic and diastolic BP in childhood and adulthood were significantly associated with higher LV mass index and LVH.
• Higher values of BMI and BP in childhood and adulthood were significantly associated with eccentric hypertrophy and concentric hypertrophy but not with concentric remodeling.

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The adverse long-term influence of obesity and elevated blood pressure on left ventricular remodeling begins in childhood, according to findings from the world’s longest running biracial heart study.

Among participants in the Bogalusa Heart Study, higher body mass index (BMI) and systolic and diastolic blood pressure in childhood and adulthood, as well as total area under the curve (AUC) and incremental AUC, were all significantly associated with higher left ventricular mass and left ventricular hypertrophy, reported Gerald S. Berenson, MD, of Tulane University School of Public Health and Tropical Medicine in New Orleans, and colleagues.

The Bogalusa study involved 1,061 adult participants who were followed as preschool and school-age children for close to 4 decades in the town of Bogalusa, La.

Previous Bogalusa study findings suggested that childhood BMI and blood pressure predict adult left ventricular hypertrophy (LVH), but data on the impact of long-term cumulative burden of obesity and elevated blood pressure on left ventricular geometric remodeling patterns since early life have not been previously reported, the researchers noted online in the Journal of the American College of Cardiology.

“By taking advantage of the longitudinal cohort of the Bogalusa Heart Study followed up from childhood, we found that the influence of adiposity measures and blood pressure levels began in early life,” the researchers wrote, adding that long-term cumulative burden and trends of BMI and blood pressure from childhood significantly predicted LVH in middle-age adults.

Study Details

Between 1973 and 2010, nine cross-sectional surveys of children (ages 4 to 18) enrolled in the study and 10 cross-sectional surveys of adults (ages 19 to 52), who had been previously examined as children were conducted, resulting in serial observations every 2 to 3 years from childhood to adulthood.

The newly published analysis initially included 1,194 adults who had recorded left ventricular dimensions in adulthood, captured from 2004 to 2010, and repeated measurements of cardiovascular risk factors from childhood to adulthood.

After excluding participants being treated for hypertension and those examined for cardiovascular risk factors less than four times, 1,064 adults remained (717 whites and 344 blacks; 42.6% men; ages 24 to 46). They underwent exams for LV dimensions at least two times each in childhood and adulthood, and were followed for a mean of 28 years.

LV dimensions were assessed by two-dimensional guided M-mode echocardiography. LV mass was calculated from a necropsy-validated formula on the basis of a thick-wall prolate ellipsoidal geometry. To take body size into account, LV mass was indexed for body height (m2.7) as LV mass index (LVMI).

The AUC was calculated as a measure of long-term burden (total AUC) and trends (incremental AUC) of BMI and blood pressure from childhood to adulthood. Four LV geometric types were defined on the basis of LVMI for body height and relative wall thickness:

• Normal or normal relative wall thickness with no LVH
• Concentric remodeling (CR) or increased wall thickness without LVH
• Eccentric hypertrophy (EH) or normal wall thickness with LVH
• Concentric hypertrophy (CH) or increased wall thickness with LVH

 

Among the findings from the analysis, LV geometric patterns differed by race, with blacks having a higher prevalence of EH than whites (17.8% versus 8.95%, P<0.001) and CH (9.1% versus 3.6%, P<0.001). CR patterns did not differ significantly by race (10.1% versus 10.9%,P=0.701).

In the total cohort, CR had a prevalence of 9.1%, while EH came in at 10.2%, and CH at 4.2%.

In four separate regression models adjusted for race, sex, and adult age, adult LVMI and LVH were significantly associated with BMI and systolic blood pressure.

In linear regression models, standardized regression coefficients of BMI (0.26-0.42) were consistently greater than those of systolic blood pressure (0.08-0.16) for LVMI. In logistic regression models, odds ratios of BMI (1.65-2.53) were consistently greater than those of systolic blood pressure (1.27-1.56) for LVH.

BMI Versus BP

The authors reported that the interaction effects of BMI with blood pressure were not significant in terms of childhood, adulthood, and total incremental AUC values on LVMI (P=0.204-0.619 for BMI with systolic blood pressure; P=0.121-0.844 for BMI with diastolic blood pressure). However, BMI-diastolic BP interaction of total AUC did reach significance (P=0.046).

In four separate regression models, adjusted for race, sex, and adult age, childhood, adulthood, total AUC, and incremental AUC values of BMI and systolic blood pressure were all significantly associated with EH and CH, but not CR.

All values of BMI also had consistently and significantly stronger associations with EH compared with systolic blood pressure.

“Importantly, this study provides strong evidence that, compared with blood pressure, BMI is more closely and consistently associated with EH using childhood, adulthood, and AUC values,” the researchers wrote. “These observations suggest that the process of LV enlargement and subclinical changes in cardiac structure are affected by a life course of excessive adiposity and blood pressure cumulatively and independently from early life, through multiple complex pathophysiological and metabolic mechanisms.”

The community-based, longitudinal cohort provided a unique opportunity to examine the relationship of cumulative life-course burden of obesity and increased blood pressure with the development of LVH and changes in cardiac structure, they said.

However, Berenson’s group noted that the exclusion of patients on blood pressure medications was a potential limitation of the analysis, “because these patients represent a subgroup with the highest blood pressure levels.”

Collaborative Data, New Insights

In an accompanying editorial, Sheldon E. Litwin, MD, of the Medical University of South Carolina in Charleston, wrote that measuring the evolution of organ damage from childhood to adulthood remains a challenge, but that the methodological tools used by the Bogalusa Heart Study researchers “should prove valuable for quantifying the cumulative burden of any risk factor or combination of risk factors over time in longitudinal studies.”

The finding that BMI is a stronger predictor of eccentric hypertrophy in adults than blood pressure differs from several other recent studies, he noted.

“Conventional thinking has held that hypertension produces concentric hypertrophy, whereas obesity is predominantly associated with eccentric hypertrophy,” he wrote, adding that the latter point of view was related, in theory, to the volume load on the heart of chronically elevated cardiac output.

“Contrary to this standard of thinking, several recent large-scale, cross-sectional studies have shown that obese adults most often had concentric, not eccentric, LV geometry,” he wrote. “The interaction of comorbidities such as increasing severity of obesity, hypertension, and nocturnal hypoxemia due to sleep-disordered breathing appeared to synergistically contribute to more severe LV hypertrophy.”

The Bogalusa researchers are currently collaborating with investigators who are conducting three other large, longitudinal, childhood-to-adulthood studies as part of theInternational Childhood Cardiovascular Cohort Consortium.

“This type of collaborative effort is highly commendable and likely to yield extraordinary new knowledge that will benefit the global health community in understanding the effects of childhood obesity,” Litwin wrote. “Although we eagerly await the insights that will emerge from the collaboration, we cannot forestall embarking on the monumental effort that will be required to find methods to control or, better yet, prevent the growing crisis of childhood obesity.”

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