BMI vs. CVD contradiction

The study observes that higher BMI is associated with higher cardiovascular mortality and morbidity. On the contrary, it is intriguing to see that CVD longevity is prolonged in adults with elevated BMI (>25) compare to those with normal BMI (19-25). A speculative explanation could be that once cardiovascular illness has been established, the high BMI-induced damage is irreversible and subsequently somewhat protective. Future research will clarify the molecular mechanisms of these observations.

GT

 

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JAMA Cardiology

Population-Based

February 2018

 

Importance

Prior studies have demonstrated lower all-cause mortality in individuals who are overweight compared with those with normal body mass index (BMI), but whether this may come at the cost of greater burden of cardiovascular disease (CVD) is unknown.

 

Objective

To calculate lifetime risk estimates of incident CVD and subtypes of CVD and to estimate years lived with and without CVD by weight status.

 

Design

In this population-based study, we used pooled individual-level data from adults (baseline age, 20-40, 40-60, and 60-80 years) across 10 large US prospective cohorts, with 3.2 million person-years of follow-up from 1964 to 2015. All participants were free of clinical CVD at baseline with available BMI index and CVD outcomes data. Data were analyzed from October 2016 to July 2017. World Health Organization–standardized BMI categories.

 

Outcomes

Total CVD and CVD subtype, including fatal and nonfatal coronary heart disease, stroke, congestive heart failure, and other CVD deaths. Heights and weights were measured directly by investigators in each study, and BMI was calculated as weight in kilograms divided by height in meters squared. We performed (1) modified Kaplan-Meier analysis to estimate lifetime risks, (2) adjusted competing Cox models to estimate joint cumulative risks for CVD or noncardiovascular death, and (3) the Irwin restricted mean to estimate years lived free of and with CVD.

 

Results  

Of the 190,672 in-person examinations included in this study, the mean age was 46.0 years for men and 58.7 years for women, and 140,835 patients (73.9%) were female. Compared with individuals with a normal BMI (defined as a BMI of 18.5-25), lifetime risks for incident CVD were higher in middle-aged adults in the overweight and obese groups.

Compared with normal weight, among middle-aged men and women, competing hazard ratios for incident CVD were

  • 1.21 and 1.32 , respectively, for overweight (BMI, 25.0-30),
  • 1.67 and 1.85 for obesity (BMI, 30.0-40), and
  • 3.14 and 2.53 for morbid obesity (BMI, ≥40.0).

Higher BMI had the strongest association with incident heart failure among CVD subtypes.

  • Average years lived with CVD were longer for middle-aged adults in the overweight and obese groups compared with adults in the normal BMI group. Similar patterns were observed in younger and older adults.

 

Conclusions

In this study, obesity was associated with shorter longevity and significantly increased risk of cardiovascular morbidity and mortality compared with normal BMI.

Despite similar longevity compared with normal BMI, overweight was associated with significantly increased risk of developing CVD at an earlier age, resulting in a greater proportion of life lived with CVD morbidity.

 

 
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