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Obesity and Life Expectancy in Older Diabetes Patients

The treatment of choice for obese T2D patients is weight loss.

The majority of patients with T2D have a high BMI of ≥ 30kg/M2. Weight loss leads to increased insulin sensitivity and an enhanced metabolic control in obese patients. Although obesity is seen and characterized as a risk factor for many conditions such as hypertension, coronary heart disease and chronic kidney disease, there is a lack of direct correlation. Being overweight is associated with twice the risk of developing cardiac and metabolic morbidities. This risk increases in proportion to the BMI.

Statistics used in this metanalysis study were hazard ratio, and 95% CI for each study, I2 statistic was used to determine heterogeneity of the studies. Statistical significance was determined using P < 0.005. This study had a total of 250,016 patients and produced results that indicated a decreased all-mortality risk for patients who were obese compared to normal weight patients. These results were not statistically significant (HR 0.87, 95% CI, 0.75 – 1.01, P = 0.058, I2 = 91.8%). Further analysis of the studies revealed that significantly lower risk of death was only observed in elderly patients but not in younger patients. (HR 0.69, 95% CI, 0.63 – 0.75, P = 0.0001, I2 = 50.4%). A lower mortality was also evident in studies that had a follow-up time of less than 10 years compared to studies that had a follow-up time of more than 10 years (HR 0.78, 95% CI, 0.65 – 0.93, P = 0.0006, I2 = 85.5%). Two more studies that were used to analyze all-cause mortality for high BMI vs normal weight patients showed consistent results of high life expectancy in older obese patients vs normal weight older patients (HR 0.84, 95% CI, 0.77 – 0.91, P = 0.0001, I2 = 91.5%). Studies that looked at BMI in relation to cardiovascular death in diabetes patients indicated a 15% reduction in risk of death in obese patients compared to normal weight patients. (HR 0.85, 95% CI, 0.74 – 0.97, P = 0.015, I2 = 12.9%).

This meta-analysis demonstrates a significantly reduced risk of death in obese patients than in normal weight patients, but longer follow-up periods reduced the benefits. This benefit of decreased risk was only observed in the elderly obese patient population. The finding of opposite relationship between obesity and mortality confirm earlier finding of a meta-analysis by Liu et al. In another study by Zoppini et al, 3,400 T2D patients were observed for 10 years and it was shown that patients who were over 65 years of age had a reduced risk of death from increased weight compared to younger obese T2D patients.

Studies suggest that increased muscle mass is associated with decreased insulin resistance. As one ages, muscle mass decreases, which results in lower body weight in the elderly patient and thus worse outcome.

Limitations of this study include inability of BMI to differentiate body fat from lean muscle. There was generalization due to many studies, which made it impossible to focus on specific patient characteristics that may differ from other patients. Most of the studies included provided baseline BMI values and weight change over time was not put into consideration.

The results of this study demonstrated a decreased risk of mortality in diabetes patients who were overweight but this benefit of increased weight and decreased risk was decreased by an increased follow-up period. Causal relationship between obesity and decreased risk was not studied requiring caution when interpreting the results of this study. A well-designed RCT is needed to study the relationship between BMI and risk reduction in T2D patients.

Practice Pearls:

  • The treatment of choice of T2D patients who are overweight is weight reduction.
  • Low mortality rate is observed in overweight diabetes patients than normal weight patients, but this benefit decreased with longer follow-up period.
  • As one ages, muscle mass decreases, which results in low body weight, hence worse outcomes.

References

Kivimäki, Mika et al. “Overweight, Obesity, and Risk of Cardiometabolic Multimorbidity: Pooled Analysis of Individual-Level Data for 120 813 Adults from 16 Cohort Studies from the USA and Europe.” The Lancet. Public Health 2.6 (2017): e277–e285. PMC. Web. 27 July 2017.

Gao F. Wang ZJ. Shen H Et al. Impact of obesity on mortality in patients with diabetes: Meta-analysis of 20 studies including 250,016 patients. Journal of Diabetic Investigation. 8 June 2017 DOI: 10.1111/jdi.12677

 

Josephat Macharia, PharmD candidate, Lecom School of Pharmacy class of 2018