ARTICLE IN BRIEF
Investigators, who analyzed data from a population-based health survey, reported that spinal cord injury (SCI) patients were 2.72 times more likely than people without a SCI to report having heart disease and 3.72 more likely to report having had a stroke.
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People with a spinal cord injury (SCI) are at significantly higher risk for heart disease and stroke, according to a new study that may prompt physicians dealing with SCI patients to pay more attention to cardiovascular health issues.
The study, based on the Canadian Community Health Survey, found that SCI patients were 2.72 times more likely than people without a SCI to report having heart disease and 3.72 more likely to report having had a stroke.
“These remarkably heightened odds highlight the exigent need for targeted intervention and prevention strategies addressing modifiable risk factors for CVD in individuals with SCI,” concluded the investigators of the study, which was published ahead of print in the July 24 edition of Neurology.
Prevention efforts could have a far-reaching affect considering that there are 200,000 people living with SCI in the U.S alone, according to government statistics.
“Over the last decade, there have been marked changes in the trends of morbidity and mortality among individuals with spinal cord injury (SCI),” the study authors said. “With advances in acute care and the management of septicaemia, renal failure and pneumonia, cardiovascular complications are now the leading cause of death in those with SCI. Moreover, several risk factors for cardiovascular disease (CVD) are amplified in individuals with SCI compared to able-bodied individuals, including physical inactivity, dyslipidemia. blood pressure irregularities, chronic inflammation, and abnormal glycemic control.”
The researchers used 2010 data complied from more than 60,000 individuals as part of the Canadian Community Health Survey. The survey uses trained interviewers to gather data from individuals aged 12 and over on a range of topics, including access to health care, health care utilization, lifestyle behaviors, socio-demographic factors, and health status. Stroke status was obtained with the question: “Do you suffer from the effects of stroke?” Heart disease status was obtained with the question: “Do you have heart disease?” Respondents were told to report only on conditions diagnosed by a health professional.
Among individuals with SCI, the prevalence of stroke was 5.7 percent compared with 1.1 percent in individuals without SCI. The prevalence of heart disease was 17.1 percent among individuals with SCI, compared with 4.9 percent in those without SCI.
After the researchers made statistical adjustments for age and sex, the risk for CVD was lower but still elevated — heart disease was 2.72 times more likely in persons with SCI and risk of stroke was 3.72 times greater.
“To put these values into context, these heightened ORs (odds ratio) reported here are similar in magnitude to the estimated ORs in the general population for the relationship between smoking and myocardial infarction (MI), diabetes and MI, and are in fact higher than those for the relationship between hypertension and MI, and abdominal obesity and MI,” the study said.
Jacquelyn J. Cragg, a PhD student at the University of British Columbia School of Population and Public Health who was the study's lead author, told Neurology Today that “there seems to be something particular about spinal cord injury that may put the individual at increased odds for cardiovascular problems.”
The researchers said that other potentially confounding factors such as hypertension, body-mass-index, smoking, and level of physical activity did not seem to explain the difference in cardiovascular risk between those with SCI and those without.
They said it was possible that the effects of SCI on the autonomic nervous system, such as blood pressure fluctuations, could explain the increased cardiovascular risk.
“Significant lability in blood pressure, from extreme hypotension during episodes of orthostatic hypotension to extreme hypertension during episodes of autonomic dysreflexia — are typical post SCI and unique features of SCI,” the study said. “Researchers have speculated that this blood pressure instability could result in vascular injury, and consequently results in greater risk for arterial disease in individuals with SCI.”
NEED TO CONSIDER CVD RISK
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Bruce H. Dobkin, MD, a professor of neurology at University of California, Los Angeles (UCLA), said the study provides important information on cardiovascular risk for physicians who care for SCI patients. Dr. Dobkin was not involved with the study.
“It means we need to pay attention to this,” he told Neurology Today. “What is missing, of course, is [the answer to the question:] ‘What is the mechanism?’”
He said the study lacks information that could shed light on that question. For instance, was the injury caused by a traumatic event or by another condition, such as multiple sclerosis? Is it a complete or incomplete SCI? What is the level of the injury? Did subjects have supine hypertension with normal sitting blood pressure?
“Patients with an injury at or above T6, for example, often have autonomic problems and wide swings in blood pressure,” said Dr. Dobkin, director of the UCLA Neurologic Rehabilitation and Research Program.
“This study is a reminder that persons with SCI have a chronic disease and chronic disability and one needs to be vigilant in looking for reversible risk factors for stroke and cardiovascular disease,” he said. He said clinicians caring for SCI patients should focus on specific preventive strategies, including achieving good blood pressure control, both supine and seated/standing, treating diabetes, and encouraging their patients to exercise the muscles they can use, not smoke and take care not to gain excessive weight.
William A. Bauman, MD — director of the National Center of Excellence for the Medical Consequences of Spinal Cord Injury, which is located at the James J. Peters VA Medical Center in the Bronx, NY — told Neurology Today that not all researchers agree that people with SCI are at heighted cardiovascular risk. A 2008 report issued by the federal Agency for Healthcare Research and Quality concluded that while the amount of research on the topic is limited, “existing evidence does not indicate that adults with spinal cord injuries are at markedly greater risk for carbohydrate and lipid disorders or subsequent cardiovascular morbidity and mortality than able-bodied adults.” It also stated that evidence did not support the use of different criteria (such as what's considered “high cholesterol”) for those with SCI compared to the general population.
However, Dr. Bauman believes there is evidence that can be extrapolated from the general population to suggest that persons with SCI are at particular risk for cardiovascular disease and that prevention-focused guidelines developed for the general population may not be sufficient for persons with paralysis. His research has found, for instance, that those with acute SCI are likely to rapidly lose lean muscle mass and gain body fat — putting on about 10 to 15 pounds of body fat in the first two years following their injury. In addition, these individuals are on the lowest end of the activity spectrum. “Taken together, these adverse changes in body composition and level of activity will have a deleterious impact on metabolism, and may lead to insulin resistance,” he said. He said that HDL cholesterol levels can be very depressed in persons with SCI — a fact that is not reflected in guidelines for managing serum cholesterol in the able-bodied population.
INFLAMMATION COULD BE A FACTOR
In addition, SCI patients tend to be in a chronic state of inflammation, with clinical or subclinical urinary tract infections, slow-to-heal wounds, and gastrointestinal irritations common, said Dr. Bauman, professor of medicine and rehabilitative medicine at Icahn School of Medicine at Mount Sinai in New York City.
The medical literature suggests that chronic inflammation and higher levels of cytokines can lead to accelerated atherogenesis. Dr. Bauman said it would be useful to have SCI-specific criteria for risk factors, such as LDL cholesterol and BMI, that would better enable physicians to optimize treatments to reduce the risk of heart disease and stroke.
Dr. Bauman said physicians caring for SCI patients need to consider the bigger picture. SCI patients tend to see a variety of specialists — physiatrist, neurologist, urologist – but none of those practitioners is necessarily prone to thinking of metabolic abnormalities and their potential adverse impact on the cardiovascular system. This means risk factors for cardiovascular disease may go unidentified, he said.
The Canadian researchers acknowledged limitations with the study. It was based on self reports, not a review of medical records. Also, since the study involved one point in time, it was impossible to tell which came first — the SCI or the cardiovascular disease. The researchers hope to do more research using more extensive data from spinal cord registries.
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Jaimie Borisoff, PhD — the study's principal's investigator and Canada Research Chair in Rehabilitation Engineering Design at the British Columbia Institute of Technology and International Collaboration on Repair Discoveries — said that while additional research is needed to explain why cardiovascular risk is higher among person with SCI, clinicians caring for SCI patients need to focus more on “how they can improve their health regardless of whether a cure (for SCI) might come down the road.'”
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