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'Exercise Cuts Stroke Risk in Elderly'
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'The risk of small brain infarcts was lower by about 40% in older people who reported high levels of physical activity'
complicating the findings somewhat, the researchers found no association between relative physical activity and total white matter hyperintensity volume as measured with MRI.
Willey and colleagues indicated that these brain abnormalities, although commonly the result of ischemic events, can have a variety of other causes too.
"While these changes can occur with chronic cerebral ischemia, nonarteriolar and nonischemic mechanisms for white matter hyperintensities have also been proposed, including endothelial dysfunction and venous sclerosis with subsequent venous hypertension," they wrote.
The signs of small brain infarcts on MRI are less ambiguous, Willey and colleagues suggested.
Another odd finding was that insurance status appeared to affect the strength of the association between activity and silent infarcts.
Highly active participants who were on Medicaid or without health insurance showed the same risk for these infarcts as did inactive participants. In contrast, the odds ratio for infarcts among highly active participants with private insurance or Medicare coverage was 0.4 (95% CI 0.2 to 0.7).
No definitive explanation was possible with the available data, but Willey and colleagues suggested one possibility.
"It may be that the overall adverse life experience for those who are uninsured or have Medicaid mitigates the protective effect of leisure-time physical activity. It is likely that being uninsured or having Medicaid is a reflection of lower socioeconomic status and is consistent with the extensive literature on social status being associated with a higher risk of cardiovascular disease independently of access to care,".
Lower prevalence of silent brain infarcts in the physically active - pdf attached
The Northern Manhattan Study
Neurology June 7 2011
"study objective- To examine the independent association between physical activity and subclinical cerebrovascular disease as measured by silent brain infarcts (SBI) and white matter hyperintensity volume (WMHV).......Engaging in moderate to heavy physical activities may be an important component of prevention strategies aimed at reducing subclinical brain infarcts.......we found that higher levels of leisure time physical activity were independently associated with a lower prevalence of SBI, but not total WMHV, in a multiethnic urban population-based cohort. Subclinical infarcts, also called silent infarcts, are more clinically significant than the name would imply, as they can have effects on functional and clinical outcomes.... It is possible that light intensity activity is also protective against SBI, but we may be underpowered to find more subtle benefits. It is important to note that light-intensity physical activity is likely to have protective effects against multiple other conditions asso-ciated with aging and our findings should not discourage individuals from performing even light intensity activities."
Subclinical cerebrovascular disease (SCVD), as manifested by subclinical brain infarcts (SBI) or white matter hyperintensities (WMH) visualized on MRI, is common in the elderly. SCVD has significant public health impact as it has been associated with impaired mobility and falls,1,2 cognitive dysfunction and dementia,3,4 and incident ischemic stroke.5
"Many of the risk factors for clinically apparent ischemic stroke are also associated with SCVD.2,6 Physical activity is a component of the guidelines for ideal cardiovascular health, which advise at least 150 minutes per week of moderate intensity, or 75 minutes of vigorous intensity activity.7 Physical activity has been associated with a lower risk of ischemic stroke in the Northern Manhattan Study (NOMAS) and others independently of other vascular disease risk factors.8,9 There has been little literature on the association between physical activity and SCVD,10,11 and few studies have included Hispanics. The purpose of this study is to examine the independent association between measures of physical activity and SCVD. We hypothesized that total physical activity would be as- sociated with a lower odds of SBI and lower WMH volumes (WMHV)."
"In our analyses, moreover, only those in the highest categories of physical activity had a reduced prevalence of SBI. We did not find an association with SBI for the third quartile of MET score or light- intensity activity. These observations are consistent with our prior finding in the NOMAS prospective cohort that only the highest levels of physical activity were inversely associated with incident ischemic stroke.8 Other groups have also found a similar threshold association with total physical activity, such that light intensity activity was not associated with risk of stroke.16,25,26 A meta-analysis summarizing the association between physical activity and ischemic stroke similarly found that higher intensity activity was consistently protective, while less intense activities were not.27"
"......physical activity has independent health benefits through modulation of inflammation, endothelial function, and vascular reactivity.28 Our findings are in keeping with the current recommendations for vascular disease primary and secondary prevention that call for a target of reasonably high intensity and energy levels of activity rather than just performing low-level activity.7,29 -31"
"An additional novel finding in our study was that moderate to heavy physical activity was not associated with a lower odds of SBI among NOMAS participants who were uninsured or had Medicaid. We did not collect information on household income, but believe that being uninsured or having Medicaid is a proxy for socioeconomic status, though it may also indicate poor access to medical care. It may be that the overall adverse life experience for those who are uninsured or have Medicaid mitigates the protective effect of leisure time physical activity. It is likely that being uninsured or having Medicaid is a reflection of lower socioeconomic status, and is consistent with the extensive literature on social status being associated with a higher risk of cardio- vascular disease independently of access to care.32"
J.Z. Willey, MD, MS Y.P. Moon, MS M.C. Paik, PhD M. Yoshita, MD, PhD C. DeCarli, MD
R.L. Sacco, MD, MS M.S.V. Elkind, MD, MS C.B. Wright, MD, MS
From the Departments of Neurology (J.Z.W., Y.P.M., M.S.V.E.), Biostatistics (M.C.P.), and Epidemiology (M.S.V.E.), Columbia University, New York, NY; Department of Neurology (M.Y.), Kanazawa University, Kanazawa, Japan; Department of Neurology (C.D.), University of California at Davis, Davis; and Departments of Neurology, Epidemiology, and Human Genetics (R.L.S.), Departments of Neurology and Epidemiology (C.B.W.), and Evelyn F. McKnight Brain Institute (C.B.W.), University of Miami, Miami, FL.
Address correspondence and reprint requests to Dr. Joshua Z. Willey, 710 West 168th Street, Box 30, New York, NY 10032jzw2@columbia.edu
Abstract
Objective: To examine the independent association between physical activity and subclinical cerebrovascular disease as measured by silent brain infarcts (SBI) and white matter hyperintensity volume (WMHV).
Methods: The Northern Manhattan Study (NOMAS) is a population-based prospective cohort examining risk factors for incident vascular disease, and a subsample underwent brain MRI. Our primary outcomes were SBI and WMHV. Baseline measures of leisure-time physical activity were collected in person. Physical activity was categorized by quartiles of the metabolic equivalent (MET) score. We used logistic regression models to examine the associations between physical activity and SBI, and linear regression to examine the association with WMHV.
Results: There were 1,238 clinically stroke-free participants (mean age 70 ± 9 years) of whom 60% were women, 65% were Hispanic, and 43% reported no physical activity. A total of 197 (16%) participants had SBI. In fully adjusted models, compared to those who did not engage in physical activity, those in the upper quartile of MET scores were almost half as likely to have SBI (adjusted odds ratio 0.6, 95% confidence interval 0.4-0.9). Physical activity was not associated with WMHV.
Conclusions: Increased levels of physical activity were associated with a lower risk of SBI but not WMHV. Engaging in moderate to heavy physical activities may be an important component of prevention strategies aimed at reducing subclinical brain infarcts.
Subclinical cerebrovascular disease (SCVD), as manifested by subclinical brain infarcts (SBI) or white matter hyperintensities (WMH) visualized on MRI, is common in the elderly. SCVD has significant public health impact as it has been associated with impaired mobility and falls,1,2 cognitive dysfunction and dementia,3,4 and incident ischemic stroke.5
Many of the risk factors for clinically apparent ischemic stroke are also associated with SCVD.2,6 Physical activity is a component of the guidelines for ideal cardiovascular health, which advise at least 150 minutes per week of moderate intensity, or 75 minutes of vigorous intensity activity.7 Physical activity has been associated with a lower risk of ischemic stroke in the Northern Manhattan Study (NOMAS) and others independently of other vascular disease risk factors.8,9 There has been little literature on the association between physical activity and SCVD,10,11 and few studies have included Hispanics. The purpose of this study is to examine the independent association between measures of physical activity and SCVD. We hypothesized that total physical activity would be as- sociated with a lower odds of SBI and lower WMH volumes (WMHV).
DISCUSSION
In our study, we found that higher levels of leisure time physical activity were independently associated with a lower prevalence of SBI, but not total WMHV, in a multiethnic urban population-based cohort. Subclinical infarcts, also called silent infarcts, are more clinically significant than the name would imply, as they can have effects on functional and clinical outcomes.3,4,6,24 In exploratory analyses in the sub- sample for whom we could calculate the HOMA index, we found that leisure time physical activity is associated with fewer silent infarcts even after adjusting for insulin resistance. Engaging in physical activ- ity may be an important strategy to reduce the prevalence of SBI and thus, potentially, improve functional outcomes.
In our analyses, moreover, only those in the highest categories of physical activity had a reduced prevalence of SBI. We did not find an association with SBI for the third quartile of MET score or light- intensity activity. These observations are consistent with our prior finding in the NOMAS prospective cohort that only the highest levels of physical activity were inversely associated with incident ischemic stroke.8 Other groups have also found a similar threshold association with total physical activity, such that light intensity activity was not associated with risk of stroke.16,25,26 A meta-analysis summarizing the association between physical activity and ischemic stroke similarly found that higher intensity activity was consistently protective, while less intense activities were not.27
Physical activity was associated with a lower prevalence of SBI independently of conventional stroke risk factors. We cannot exclude the possibility of residual confounding, though physical activity has independent health benefits through modulation of inflammation, endothelial function, and vascular reactivity.28 Our findings are in keeping with the current recommendations for vascular disease primary and secondary prevention that call for a target of reasonably high intensity and energy levels of activity rather than just performing low-level activity.7,29 -31
An additional novel finding in our study was that moderate to heavy physical activity was not associated with a lower odds of SBI among NOMAS participants who were uninsured or had Medicaid. We did not collect information on household income, but believe that being uninsured or having Medicaid is a proxy for socioeconomic status, though it may also indicate poor access to medical care. It may be that the overall adverse life experience for those who are uninsured or have Medicaid mitigates the protective effect of leisure time physical activity. It is likely that being uninsured or having Medicaid is a reflection of lower socioeconomic status, and is consistent with the extensive literature on social status being associated with a higher risk of cardio- vascular disease independently of access to care.32
We did not, however, find an association between physical activity and WMHV. Others have also failed to find an association between physical activity and WMHV. In the NHLBI Twin Study, physical activity was not associated with WMHV, while it was associated with other measures of brain morphology.10 In the Cardiovascular Health Study, physical activity was not associated with WMHV at baseline, or with worsening over time.2 The explanations for the lack of association between physical activity and WMHV could be due to the heterogeneity of pathology underlying WMHs. While evidence links a heavy burden of WMHs to numerous vascular risk factors, retinal vascular changes,33 subcortical cerebral infarction, and intracerebral hemorrhage,34 the pathologic basis remains poorly characterized, with only small series providing definite pathologic correlation with MRI. In many of the pathologic series, cellular changes in myelin, astrocytes, and endothelial cells are seen in areas of affected white matter, with concomitant blood- brain barrier breakdown. While these changes can occur with chronic cerebral ischemia,35 nonarteriolar and nonischemic mecha- nisms for WMHs have also been proposed, including endothelial dysfunction and venous sclerosis with subsequent venous hypertension.36,37 While nonisch- emic lesions can be mislabeled as infarcts, SBI may be less prone to misclassification and, unlike WMHs, they share many of the pathologic features of clinical lacunes38 and have similar risk factors, including physical inactivity.
Our study has important strengths, with a large proportion of participants who are Hispanic, older, with Medicaid or no insurance, and urban dwelling, all of which have been underrepresented in previous studies of risk factors and measures of SCVD. Previous studies on the association between physical activity and cardiovascular disease are often difficult to interpret given the variable methods used to categorize physical activity. In our study we characterized physical activity by several methods.
Our study also has some important weaknesses, however. Risk factors for SBI and WMH were measured several years before MRI, and it may be that changes in risk factor status may be more informative than measurement at one time.39 We adjusted for time between the physical activity questionnaire and MRI and noted that our results did not change. Furthermore, our methodology makes it less likely that participants engaged in less physical activity because of the findings on MRI and allows us to gain additional information from a temporality. We did not have available direct measures of physical fitness, though in previous studies questionnaires correlate well with measures of oxygen consumption.14 It is possible that light intensity activity is also protective against SBI, but we may be underpowered to find more subtle benefits. It is important to note that light-intensity physical activity is likely to have protective effects against multiple other conditions asso-ciated with aging and our findings should not discourage individuals from performing even light intensity activities. Finally, as with any epidemio- logic study, it is not possible to establish causation. A decline in physical activity is a hallmark of frailty, which in and of itself may be partly influenced by SCVD.40 Further studies will be required to clarify these causal pathways.
In our study, we found that physical activity was associated with a reduced prevalence of SBI, but not WMHV. This may have potential therapeutic implications given the multiple adverse health outcomes associated with SBI in older individuals. These interventions will however have to consider socioeconomic status and access to care limitations so as to gain the maximum benefit from exercise.
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