Exercise is Medicine
The Dose response associated with chronic diseases
There is overwhelming evidence that fitness is associated with a wide range of health outcomes that include respiratory disease, digestive and colorectal cancer, as well as circulatory disease and all- cause mortality.
Furthermore, these associations are independent of potential measured confounding factors, ranging from socio demographics, diet, adiposity, watching TV and self- rated health.
The body depends on oxygen to meet its metabolic and respiratory demands. An obstruction to easy flow of oxygen compromises this and leads to deterioration in respiratory and metabolic processes and ultimately may result in death. Chronic obstructive pulmonary disease ( COPD)
represents an increasing public health burden globally, and is in the top five leading causes of mortality world- wide.
The underlying mechanisms remain to be fully established and are likely multifactorial in nature.
One potential mechanism could be due to a higher fitness being associated with lower levels of inflammation, which plays a pivotal role in the disease process of COPD.
As noted in previous series, the effect of fitness against all- cause mortality and circulatory disease ( CVD) events were reported, that those with low fitness to be at 56percent increased risk of all- cause mortality and 47percent increased risk of CVD incidence, compared with those with intermediate fitness. The magnitude of the association was greater in comparison with high fitness individuals. Shuval et al, in a more recent study of 3141 participants, reported those in the intermediate and high fitness groups to be at 20percent and 24percent reduced hazard of all- cause mortality, respectively, after long- term ( median 28 years) follow- up. These findings suggest that fitness is a useful clinical indicator for both short- and long- term mortality risk.
What is also evident from these studies is that there is not a strong dose– response relationship evident between fitness and every health outcome. An observational study by Stell et al, is not able to uncover the underlying mechanisms but it may be that for certain conditions, such as circulatory disease, there is a threshold effect after which no further benefits of higher fitness are found.
EXERCISE IS MEDICINE: The Dose response association with chronic diseases
The majority of previous studies demonstrate that higher levels of fitness may result in protective effects against all- cancer mortality with limited evidence demonstrating an association between fitness and specific cancers.
Previous publications from the Aerobics and Cooper Center Longitudinal Studies reported that, when compared with unfit men, fit men had lower colorectal cancer incidence. Similar results have been reported by Thompson and colleagues, in men with pre- diabetes and diabetes.
Contrary to the potential health benefits, there are findings that a high level of fitness (> 10 METs) to be associated with higher risk of incident atrial fibrillation and prostate cancer. This describes the J curve association relating to the degree of physical intensity and mortality. This
Means there is a considerable level where a sustained higher intensity puts one at more risk of sustaining atrial fibrillation compared with those of moderate intensity.
There is propelling evidence that higher fitness is associated with lower CVD disease and all- cause mortality. It is demonstrated that fitness is also associated with wider health outcomes including respiratory disease and colorectal cancer.
Although fitness has an important genetic component, regularly performing moderate to vigorous intensity, endurance- based activities ( eg, brisk walking, running, cycling) can increase fitness. Such exercise training ( ranging from 4 to 36 weeks) can increase fitness by ≥ 1MET(~ 10percent) in a range of adult populations ( eg, healthy, obese, heart disease, hypertension and diabetes), which highlights that the majority of adults in the population can acquire clinically important gains in fitness.
Journal article source:
Steell L, Ho FK, Sillars A, et al. Br J Sports Med Epub 2018. doi: 10.1136/ bjsports- 2018- 099093