Does Being Fit Help Reduce Risk of Death in Women With with Metabolic Syndrome?
In the past, we have published a couple of blogs on the topic of metabolic syndrome (MetSyn). To refresh your memory, MetSyn is a very common condition where three or more of the following cardiovascular disease risk factors are present. This is sometimes referred to as ‘"risk factor clustering.’ "
-Fasting blood triglyceride level >150 mg/dL
-Blood HDL cholesterol level: Men, <40 mg/mL; <50 mg/dL in women
-Waist circumference: Men, >40 inches; >35 inches in women
-Resting blood pressure >130/85 mmHg or on blood pressure medication
-Fasting blood glucose level >100 mg/dL or on diabetes medication
Currently, nearly 100 million American adults have MetSyn, which is strongly associated with an increased risk of developing type 2 diabetes, cardiovascular disease, and some cancers. One of the root causes of MetSyn is a condition known as insulin resistance, where the pancreas is producing insulin but the tissues are resistant to its effects. Insulin resistance is most commonly seen in middle-aged to older adults who are sedentary and overweight, but it can be seen in younger individuals as well. Genetics can also predispose individuals to being insulin resistant.
Cardiorespiratory fitness (CRF) is defined as the body’s ability to utilize oxygen at the cellular level, and can be objectively measured by maximal treadmill exercise testing. The treadmill test is one of the important cornerstones of a preventive medical exam at the Cooper Clinic. Research, including findings from the Cooper Center Longitudinal Study (CCLS), shows it has been well known for many years that individuals with moderate to high levels of CRF are substantially less likely to currently have or to develop MetSyn in the future. The Cooper Center Longitudinal Study (CCLS) has made important contributions to this area of research. To put it simply, having a moderate to high level of CRF seems to make insulin work better. Rather than being insulin resistant, fit individuals tend to be insulin sensitive. In other words, a little bit of insulin goes a long way if you are fit.
However, less is known regarding the effects of CRF on mortality risk in women who have MetSyn. To that end, my colleagues and I recently published a study on 1,798 women with MetSyn who were examined at the Cooper Clinic. Based on the results of their treadmill exercise test and their age, women were placed into two broad categories of CRF:
During an average follow-up period of 17 years, 204 women died; the majority of deaths were from cardiovascular disease and cancer. After taking age, smoking, and length of follow-up into account, the mortality risk for the two fitness categories is displayed below in the Figure.
As shown above, Unfit women with MetSyn were 36% more likely to die during follow-up as compared to Fit women with MetSyn. We believe that ours is the first study to report on these findings in women; a similar study was published on Cooper Clinic men in 2004.
The take-home message is that women with metabolic syndrome should strive for a moderate level of cardiorespiratory fitness in order to reduce the risk of premature death. Meeting the most recent guidelines for physical activity is the most effective strategy for achieving this goal.
Farrell, S.W., et al. (2023). Cardiorespiratory fitness and all-cause mortality in women with metabolic syndrome. Metabolic Syndrome and Related Disorders. Published ahead of print. February 27, 2023.
Farrell, S.W., et al. (2004). Prevalence of the metabolic syndrome across cardiorespiratory fitness levels in women. Obesity Research. 12(5):824-830.
Katzmarzyk, P.T., et al. (2004). Cardiorespiratory fitness attenuates the effects of the metabolic syndrome on all-cause and cardiovascular disease mortality in men. Archives of Internal Medicine. 164:1092-1097.