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Population studies

Obesity-related diseases can decrease life by 11 years

Decreased life years dependent on gender, race, BMI classification and age

Obesity-related diseases (ORDs) such as coronary heart disease, hypertension, diabetes, and stroke can increase the chances of dying and decrease life years by 0.2 to 11.7 years, according to a study, 'Life Years Lost Associated with Obesity-Related Diseases for US Non-Smoking Adults', published online in the journal Plos One.

The study authors from Washington University School of Medicine, St Louis, said that reduced life expectancy is dependent on gender, race, BMI classification and age.

“The life years lost associated with ORDs was more pronounced for younger, black, male, and more obese adults than for older, white, female, and less obese adults”, they write. “To our knowledge, none has focused on the incidence of ORDs or the association of ORDs with mortality and life expectancy.”

The research was designed to predict the life years lost associated with obesity-related diseases (ORDs) for US non-smoking adults and to examine the relationship between those ORDs and mortality.

Study design

The researchers used data from the National Health Interview Survey (1997–2000). Age at death or censor was the outcome variable and they included gender, race, educational attainment, alcohol consumption, and physical activities in each model.

The ORDs included in the study were coronary heart disease, hypertension, diabetes, and stroke. In addition, age and divided the groups into the ages 20 and 29, 30 and 39, 40 and 49, 50 and 59, 60 and 69, and 70. BMI classifications were based on the standards established by the World Health Organization.

The life years lost was predicted by simulating life years for populations with at least one ORD and without ORDs based on the estimates in the final model. They divided the sample into groups with different combinations of race, gender, age, and BMI classification.

They subsequently simulated their survival densities based on the parameter estimates in the final model and predicted life years. “Life years lost was projected by comparing the predicted life years of people with ORDs to that of people without ORDs within the same group,” the authors explain.

Results

They report the life years lost associated with ORDs is more marked for younger adults than older adults, for blacks than whites, for males than females, and for the more obese than the less obese (Figure 1). They found that the mean life years lost associated with ORDs for US non-smoking black males aged 40 to 49 years with a BMI >40 was 5.43 years, which translates to a 7.5% reduction in total life years. White males of the same age range and same degree of obesity lost 5.23 life years on average – a 6.8% reduction in total life years, followed by black females (5.04 years, a 6.5% reduction in life years), and white females (4.7 years, a 5.8% reduction in life years). Overall, ORDs increased chances of dying and lessened life years by 0.2 to 11.7 years depending on gender, race, BMI classification, and age.

Figure 1: Life years lost associated with obesity-related diseases for US white and black, male and female, overweight and obese, non-smoking adults

An additional ORD was associated with an increase in risk of death for every age group, though mortality risk was more severe for younger individuals: 5.11 [95% CI: 3.85–6.79] for ages 20 to 29; 3.05 [95% CI: 2.31–4.02] for ages 30 to 39; 2.49 [95% CI: 2.09–2.98] for ages 40 to 49; 2.07 [95% CI: 1.71–2.50] for ages 50 to 59; 1.87 [95% CI: 1.63–2.14] for ages 60 to 69; and 1.34 [95% CI: 1.24–1.44] for ages 70 and above (Figure 2).

Figure 2: Marginal effect of obesity-related diseases on mortality rate for each age group

With regard to BMI, they reported that found that the underweight, class II, and class III obese had higher mortality rates than the normal-weight (Figure 3). The class III obese had the highest hazard ratio (1.69 [95% CI: 1.37–2.08]) compared to normal-weight people, followed by the underweight (1.54 [95% CI: 1.39–1.70]), and the class II obese (1.28 [95% CI: 1.14–1.44]). The overweight (0.90 [95% CI: 0.84–0.96]) and class I obese (0.997 [95% CI: 0.91–1.09]) had lower death rates than the normal-weight, but the latter was not statistically significant.

Figure 3: Hazard ratios for death for each BMI classification (reference: the normal-weight

Conclusion

“Our results confirm that being obese or underweight increased risk of mortality…This conclusion not only conveys a message that these populations are more vulnerable to ORDs, but it also informs policy makers that public health initiatives should put more emphasis on the prevention of obesity and obesity-related comorbidities for these populations,” the authors concluded. “More importantly, future studies should investigate how different ORDs separately observed at different life stages impact life years lost.”

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