ReviewThe effect of walking on risk factors for cardiovascular disease: An updated systematic review and meta-analysis of randomised control trials
Introduction
Physical inactivity is the fourth leading cause of global mortality (World Health Organisation, 2009) responsible for 6–10% of the major non-communicable diseases of coronary heart disease, type 2 diabetes, and breast and colon cancers (Lee et al., 2012). Whilst sport, running and vigorous gym based exercise are often seen as counter measures, walking offers a natural, widely accepted, low cost, low injury risk (Hootman et al., 2001) and environmentally friendly approach to physical activity which can be incorporated into activities of daily living and/or undertaken recreationally. Walking is also likely to be more accessible and suitable to a considerable portion of the higher-risk population who may be obese, sedentary, at high risk of cardiovascular disease and for whom strenuous forms of exercise may be unsuitable. Walking at a self-selected pace is moderate intensity for most adults (Ainsworth et al., 2000, Murtagh et al., 2002). Indeed it is estimated that walking at 3 mph would be vigorous intensity for approximately 20% of the population (Kelly et al., 2011). Systematic reviews have indicated that inactive people can be encouraged to walk more by tailored interventions (Ogilvie et al., 2007) and the National Institute for Health and Clinical Excellence has recently produced guidelines to promote walking for travel and recreational purposes (National Institute for Health and Clinical Excellence, 2012).
Whilst it is unsurprising that walking has become a cornerstone of physical activity promotion strategies, a challenge faced by healthcare professionals and patients is knowing the effects of walking on health, especially as many published walking interventions employ relatively small samples and findings are often inconsistent between studies. Conversely, the use of meta-analysis increases the precision and accuracy of the estimates of the effects of walking, quantifies the inconsistency between studies and enhances generalizability to a larger population. We previously reported a meta-analysis of walking interventions published up to 2004, that included aerobic fitness, blood pressure, and body composition (Murphy et al., 2007). Since then there has been an increase in the number of published interventions examining the effects of walking on risk factors for cardiovascular disease. In addition, an increased range of outcome measures have been included in these studies, such as blood lipids and several measures of adiposity. Whilst there is now greater evidence of the concomitant dangers of these factors to public health (Physical Activity Guidelines Advisory Committee, 2008) a recent comprehensive synthesis of evidence from randomised control trials on the effect of walking on health is lacking. This updated meta-analysis therefore expands our understanding of the treatment–effect relationship between walking and health.
The objective of this study was to assess the effect of walking interventions on risk factors for cardiovascular disease in previously inactive adults. This updates our previous review and provides healthcare professionals with a synthesis of the effects accruing when inactive adults undertake a walking programme.
Section snippets
Methods
We followed the PRISMA statement (preferred reporting items for systemic reviews and meta-analyses) in conducting and reporting the meta-analysis (Moher et al., 2009). A review protocol has not been published separately.
Study selection
A total of 210 articles were identified by electronic searches and 16 articles from hand-searching. Thirty one duplicates were then excluded. After reviewing the title and abstract of the 195 articles identified, 150 were excluded as they did not meet the inclusion criteria. The full text versions of 45 articles were then reviewed. Fifteen studies were deemed eligible for inclusion in the study and combined with studies reported in our previous meta-analysis (Murphy et al., 2007) (n = 17).
Discussion
This updated systematic review and meta-analysis suggests that walking programmes improve several markers of cardiovascular risk, including aerobic capacity, systolic and diastolic blood pressure, and adiposity (waist circumference, body mass, percentage body fat and body mass index) in previously inactive but apparently healthy adults. However there was no evidence of changes in total cholesterol, HDL cholesterol, LDL cholesterol or waist-to-hip ratio. In this updated meta-analysis we analysed
Conclusions
Our findings confirm the important role that regular walking can play in the prevention of cardiovascular disease. The meta-analysis revealed positive changes for multiple cardiovascular disease risk factors, including aerobic fitness, systolic and diastolic blood pressure, and several measures of adiposity in previously inactive adults who walked as part of a randomised controlled trial. Clinicians and health-care providers can prescribe walking with confidence that it will evoke health
Conflict of interest statement
The authors declare that there are no conflicts of interest.
Acknowledgments
Funding was received from the Mary Immaculate College Research Directorate Seed-funding scheme for assistance with data extraction. This funder had no role in the study.
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