Signature Methods

• April 19, 2016
• by Kristofer
• in Disease prevention, Educational

Physical activity is a therapeutic, medicinal strategy to combat the leading causes of death world-wide. Currently the top two leading causes of death world-wide (ischemic heart disease & stroke) out total the next eight leading causes of death combined (World Health Organization, 2014). One of the primary causes of ischemic heart disease and the most common form of stroke is atherosclerosis. Atherosclerosis is the buildup of fats, cholesterol, and other substances in and on the artery walls which results in restricted blood flow. Risks for both of these leading causes of death revolve around high blood cholesterol and triglyceride levels. A condition called dyslipidemia refers to hypercholesterolemia, high triglycerides, or low levels of high-density lipoprotein cholesterol (HDL-C) (Dishman, Health & Lee, 2013). Hypercholesterolemia refers to levels of total serum cholesterol that exceeds the population average of 200 mg/dl among adults. Cholesterol is a waxy, fat-like substance that travels through the bloodstream in small packages called lipoproteins. There are two types of lipoproteins: low-density lipoprotein cholesterol (LDL-C), often referred to as bad cholesterol, and high-density lipoprotein cholesterol (HDL-C), commonly called good cholesterol. Low-density lipoprotein carries cholesterol to tissues, including the arteries leading to the heart and the brain which can lead to build up on the arterial walls. High-density lipoprotein helps remove cholesterol from the arteries. When the LDL level is great or the HDL level is low, the risk of coronary heart disease, ischemic stroke, and thromboembolic stroke increases.

Coronary heart disease, ischemic stroke, and thromboembolic stroke result from the blockage of the arteries supplying blood to the heart or brain. Ischemic heart disease refers to an impedance or blockage of one or more arteries that supply blood to the heart, usually due to atherosclerosis. A stroke is the loss or impairment of bodily function resulting from injury or death of brain cells consequent to insufficient blood supply. About 85% of strokes are classified as primary ischemic or thromboembolic strokes (Dishman et al., 2013). They result from thrombosis (clotting in a vessel) or stenosis (narrowing of the artery), usually from atherosclerosis, or from an embolism (occlusion of a vessel by a circulating atheroma or clot, often from the heart). The stenosis of an artery often begins in childhood, and its severity is related to the level of blood cholesterol and its lipoprotein constituents. As mentioned, low-density lipoprotein (LDL-C) cholesterol accelerates atherosclerosis, while high-density lipoprotein (HDL-C) cholesterol retards it.

Increased high-density lipoprotein cholesterol has been shown to be protective against cardiovascular disease, and associated with reduced risk of ischemic stroke in the elderly and among different racial groups (Sacco, Benson, Kargman, Boden-Albala, Tuck, Lin, Cheng, Paik, Shea, Berglund, 2001). Aerobic exercise at a moderate intensity has shown to significantly increase HDL-C over the short course of six months (Duncan, Gordon, & Scott, 1991). High amounts of weekly exercise, even without weight loss, has widespread beneficial effects on the lipoprotein profile (Kraus, Houmard, & Duscha, 2002). These improvements are related to the amount of activity and not the intensity of exercise or improvement in fitness. The lipoprotein profile is associated with hypercholesterolemia and the total serum cholesterol level. Increasing HDL-C and lowering LDL-C will enhance reductions of risk for both types of stroke and CHD.

A 10% decrease in total blood cholesterol levels may result in an estimated 20% to 30% reduction in the incidence of CHD (Dishman et al. 2013). The overall evidence that regular aerobic or endurance exercise can improve lipoprotein profiles is encouraging. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triglycerides, TC low-density lipoprotein cholesterol (LDL-C) ratio and the atherogenic index of plasma were significantly lower in both categories of professional athletes than the sedentary participants (Lippi, Schena, Salvagno, Montagnana, Ballestreiri, & Guidi, 2006). Mean HDL-C concentration was significantly higher in the professional athletes as well. Based on the evidence, aerobic exercise expending between about 1200 and 2400 kcal each week for at least 12 weeks and conducted at moderate or vigorous intensities yields favorable changes in lipoprotein profiles (Dishman et al., 2013). The best available evidence suggests that increases in HDL and decreases in triglycerides and LDL in people with dyslipidemia are dose dependent on total energy expenditure, more so than exercise intensity, occurring after thresholds of 10 to 13 MET-hours per week of physical activity (Kodama, Tanaka, Saito, Shu, Sone, Onitake, Suzuki, Shimano, Yamamoto, Kondo, Ohashi, Yamada, & Stone, 2007).

The relationship between dyslipidemia, cardiovascular disease, and stroke appears to be clear and direct. The medical cost of cardiovascular disease and stroke related to dyslipidemia were estimated to exceed $400 billion in 2006 (Smith, 2007). The total costs included medical services and lost wages. The cost for lipid lowering treatment on average saved $15,000 to $20,000 per life-year saved. In some low-risk cases, treatment saved up to $490,000 per lifetime.

When considering dyslipidemia and its associated risks of coronary heart disease and stroke, its obvious that physical activity is an important part of prevention. Taking group classes like power & acroyoga, walking the dog at the dog park, playing a game of kickball with the friends, or even cleaning around the house will all improve your health. Just remember, the intensity is less important while the duration of activity is.

Now that we’ve addressed one of the major contributors to the most common forms of stroke and coronary heart disease, let’s address what else we can do to lower their risks. The economic burden of CHD was estimated at $177 billion in 2010 in the United States alone (Dishman et al. 2013). Coronary heart disease is a major contributor to disability and lost productivity in the economy. CHD also takes many lives annually (425,000). Coronary heart disease accounts for over 50% of cardiovascular deaths and 1 of 6 deaths each year in the United States. CHD has led the way as the leading cause of death worldwide for nearly a century (World Health Organization, 2014).

Physical activity level is important, but so is the amount of time we are sedentary. The time spent sitting is directly related, in a dose-response fashion, to cardiovascular disease mortality (Katzmarzyk, Church, Craig, & Bouchard, 2009). Physical activity shows a curvilinear dose-response relationship with CHD risk (Sattelmair, Pertman, Ding, Kohl, Haskell, & Lee, (2011). An amount of energy expenditure equivalent to 150 min/week of moderate-intensity aerobic activity, or 75 min/week of vigorous-intensity aerobic activity, or a combination of the two that generates equivalent energy clearly is associated with reduction in rates of CHD (U.S. Department of Health and Human Services, 2008). Additional reductions in CHD rates occur with 300 min/week of moderate-intensity, or 150 min/week of vigorous-intensity aerobic physical activity, or an equivalent combination of the two.

Physical activity shows promising associations with reductions in CHD risk. Participants who engaged in 150 minutes of moderate-intensity leisure activity had a 14% lower risk of coronary heart disease compared with those who reported no exercise or physical activity (Medical Economics, 2011). Participants who engaged in more than 150 minutes gained additional benefits and those who engaged in less than 150 mintues still had a lower risk of CHD than those who reported no activity. Since health is related to both sedentary and physical activity levels it’s important to address both. Disconnecting the cable for an extended period of time like a summer or a given month will decrease sitting time. Parking as far from the front door of the place you are going is a great way to increase activity level. Another challenge is taking the stairs whenever possible. Getting off the bus or subway one stop early and walking the rest of the way is another fantastic option for increasing activity levels. No matter what you choose to do for physical activity, make sure it is at a moderate to vigorous intensity and long enough to match the guidelines above.

Reducing the prevalence of cerebrovascular disease (stroke) is extremely important. 610,000 adults 20 years and older have their first stroke each year in the United States. Another 185,000 have a recurrent stroke, and about 160,000 die from stroke-related causes (American Heart Association, 2012). The direct and indirect economic cost of stroke in the United States for 2010 was estimated at $73.7 billion (American Heart Association, 2012). Physically active men and women generally have a lower risk of stroke incidence or mortality than the least active, with more active persons demonstrating a 25% to 30% lower risk for all strokes (including ischemic and hemorrhagic stroke) (U.S. Department of Health and Human Services, 2008). The evidence for a dose-gradient reduction in stroke risk with increasing weekly energy expenditure or a higher intensity of physical activity is less clear than for CHD. It appears that increased physical activity is associated with a reduced risk of atherosclerosis and blood clotting (Dishman et al. 2013). Optimal levels of intensity and duration of physical activity have eluded scientists when considering reductions in risk of stroke. However, a decreased risk was observed at energy expenditures of 1000 to 1999 kcal/week, with further risk diminishment seen at 2000 to 2999 kcal/week (Lee, & Paffenbarger, 1998). Although an optimal level of intensity nor duration of physical activity has not been found for reducing risk of stroke, physical inactivity is associated with greater risk of having a stroke (Boden-Albala, Sacco, 2000). Physical activity itself has shown to decrease risk of stroke, as well as provide a preventative measure by increasing blood flow to the brain (Endres, Gertz, Lindauer, Katchanov, Schultze, Schrock, & Laufs, 2003). Taking a dance class, playing a sport, power walking around the block, and performing household chores are all viable options to stay active and reduce the risk of stroke.

The double edged sword of stroke and coronary heart disease are both related to another disease known as dyslipidemia. Physical activity has a positive affect on reductions in the risks of all three of these health concerns while physical inactivity predisposes us to them. Finding manageable and maintainable ways to stay physically active is ideal. Following the guidelines of the U.S. Department of Health and Human Services, 75 minutes of vigorous-intensity exercise and 150 minutes of moderate-intensity exercise per week should be enough to keep you on your feet and these diseases at bay, so get out and go do!

References

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