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Obesity and Its Effects on Mortality Rate

Does obesity increase or decrease death rate?

Obesity is connected to a variety of cardio metabolic diseases such as type 2 diabetes mellitus (T2DM), hypertension, hyperlipidemia, metabolic syndrome and cardiovascular disease (CVD), all of which contribute to increased mortality. Also, a number of epidemiologic surveys have indicated that individuals otherwise healthy and lacking any detectable diseases or health risks are at a higher risk of cardio metabolic dysfunction and mortality if they are overweight or obese. The world Health Organization (WHO) has recommended classifications of body weight based on body mass index (BMI), calculated as weight in kilograms divided by height in meters squared (kg/m2) as a substitution for thinness and fatness. BMI is an independent risk factor for increased all-cause mortality in the general population. BMI from 18.5 to 25 is categorized as normal, 25-30 as overweight, 30-35 as moderately obese, and over 40 as severely obese. Overweight and obese people are more likely to be affected by cardiovascular events than people of normal weight. Scientists say overweight people die one year earlier than expected and moderately obese people die up to three years prematurely. However, severe obesity could cost as much as eight years of life. For these reasons, physicians have advised against being overweight; carrying too much weight is second to smoking as cause of premature death.

The aim of this study is to investigate the association between BMI and all-cause mortality in Taiwanese patients with T2DM to define optimal body weight for health. There were 2161 T2DM patients, and excluded patients were acute myocardial infarction, heart failure, stroke and ESRD. Baseline included medical history and laboratory tests were measured. Patients were followed every 2 to 6 months for lab values to be reevaluated. Weight and height were measured and BMI calculated. All statistical operations were carried out using SAS version 9.4. One hundred and nineteen patients died during the followup period. Those with BMI < 22.5 kg/m2 had significantly elevated all-cause mortality as compared with those with BMIs 22.5 to 25.0kg/m2. (BMI 17.5-20.0 kg/m2; HR 1.989, P < 0,001; BMI 20.0-22.5 kg/m2: HR 1.286, P= 0.02) as did those with BMIs > 30.0 (BMIs 30.0-32.5 kg/m2: HR 1.670, P < 0.001: BMIs 32.5-35.0: HR 2.632, P< 0.001). This study had a number of limitations, such as the duration of the diabetic patients varied, and BMI could not be calculated at the time of their diagnosis. A U- shaped relationship between all- cause mortality and BMI in patients with T2DM in Taiwan, irrespective of age, sex and smoking status, was shown. Those with BMI of ≥30 kg/m2 are at higher risk of mortality, and weight management should be strongly recommended.

Another study was conducted in Germany to analyze the association between BMI and all-cause mortality in patients with and without diabetes using established data. All patients registered between 1 January 2000 and 31 December 2008 who reached the hospital alive and survived more than 28 days after Acute MI.  After exclusions the final data set comprised 4054 patients. Participants were interviewed using a standardized questionnaire. BMI is measured and classified under normal, overweight and obesity. Information provided by patients was verified on the patients’ chart. Vital status was monitored through the population registries and outcome was determined to be an all-cause mortality. ANOVA was used for the data analysis. Patients with diabetes had a higher long term mortality rate (40 deaths per 1000 person years; n =273) than patients without diabetes (21 deaths per 1000 person years; n=366). With 50 deaths per 1000 person years (n=66) and 26 deaths per 1000 person years (n=135) normal weight individuals had the highest long term mortality rate both among patients with and without diabetes respectively. Overweight patients without diabetes had a statistically significant 0.73-fold risk of dying (95% CI 0.58-0.93; P = 0.009) and obese patients without diabetes had even lower HR of 0.64 (95% CI 0.47-0.87; P= 0.004) compared with normal weight patients. A few limitations of this study included the fact that information on other relevant conditions affecting survival after AMI were not collected. Also, patients with type 1 diabetes only accounted for 2.1% of the study population with diabetes mellitus.

In conclusion, AMI patients without diabetes detected a significant protective effect of overweight and obesity on all-cause mortality, which diminished with increasing observation while remaining statistically significant. However, in AMI patients with diabetes being overweight or obese did not result in survival benefit.

Practice Pearl:

  • Obesity is connected to a variety of cardio metabolic diseases such as type 2 diabetes mellitus (T2DM), hypertension, hyperlipidemia, metabolic syndrome and cardiovascular disease (CVD), all of which contribute to increased mortality.
  • AMI patients without diabetes detected a significant protective effect of overweight and obesity on all-cause mortality which diminished with increasing observation while remaining statistically significant.
  • However, in AMI patients with diabetes being overweight or obese did not result in survival benefit.

References

Colombo, Miriam Giovanna et al. “Association of Obesity and Long-Term Mortality in Patients with Acute Myocardial Infarction with and without Diabetes Mellitus: Results from the MONICA/KORA Myocardial Infarction Registry.” Cardiovascular Diabetology 14 (2015): 24. PMC. Web. 18 July 2016.

Kuo, Jeng-Fu et al. “The Association between Body Mass Index and All-Cause Mortality in Patients with Type 2 Diabetes Mellitus: A 5.5-Year Prospective Analysis.” Ed. Kistner. Anna. Medicine 94.34 (2015): e1398. PMC. Web. 18 July 2016.