As the adoption of physical activity is a complex behavior, varying degrees of participation were observed in the community: 54.6% of the subjects complied with walking on more than four days a week, while 32.2% engaged in brisk walking on one to four days a week; the dropout rate was 13.2%. Earlier studies on the promotion of physical activity have shown dropout rates ranging from 0 to 60% and compliance ranging from 53 to 100%.[19
] Another study observed a dropout rate of 33% in the intervention group, at the end of 24 weeks.[20
] The present study has demonstrated that it is feasible to motivate a community in a low resource setting to undertake a behavior-related non-pharmacological intervention.
This study has proved that a 10-week intervention to promote physical activity was effective in significantly reducing population mean BP by 1.56 / 0.74 mm Hg by the ‘Intention to Treat’ analysis and 1.82 / 0.87 mm Hg by the ‘Per Protocol’ analysis. The magnitude of BP response varied across studies, depending on the type of study (original study or meta-analysis), study setting (community or clinic based), duration of the study, type of participants (free or paid volunteers), methods of promoting physical activity, type and intensity of physical activity, techniques of monitoring compliance (investigator or group monitoring or no monitoring), reporting of physical activity (self-reported, group attendance or pedometer-based), and type of analysis (Per Protocol or Intention to Treat). Given the wide heterogeneity in study methodologies, comparison with other studies is difficult, but the public health implications of the significant BP reduction observed in this study can be illustrated as follows: It has been estimated that a 2 mm Hg downward shift in the distribution of SBP is likely to reduce annual mortality from stroke by 6%, CHD by 4%, and all causes by 3%. Mortality due to CHD, stroke, and all causes in India was 0.8[7
] and 7.4[21
] per thousand (2008). It can be calculated that for a population of one million, the intervention effect of 1.56 mm Hg would result in an annual reduction of 25, 28, and 173 deaths due to CHD, stroke, and all causes, respectively, provided the population engages in physical activity of 30 minutes / day, four days a week.
In this study, the BP-lowering effect of brisk walking was more pronounced in hypertensives (4.5 / 2.74 mm Hg) compared to normotensives (1.55 / 0.69 mm Hg). This concurred with findings of several meta-analyses[22
] and the World Hypertension League, which stated that BP reduced by 11 / 6 mm Hg in hypertensives and 4 / 4 mm Hg in normotensives, in response to physical activity.[12
] SBP reduction of 5 mm Hg in hypertensives has the potential to reduce mortality from CHD, strokes, and all causes by 9, 14, and 7%, respectively.[25
] The reduction of a 5 mm Hg SBP in hypertensives exhibited in this study proves the public health significance of the promotion of physical activity intervention in hypertensives as well. Regular exercise is also known to affect other cardiovascular risk factors favorably, such as, dyslipidemia, insulin resistance, body weight, arterial compliance, left ventricular hypertrophy, or impaired cardiovascular reflex control. Given the additional benefits and better acceptability as a lifestyle modification,[16
] hypertensives should engage in regular physical activity.
However, the fact that hypertensives have higher BP reduction than normotensives does not undermine the importance of physical activity in the normal population; the significant BP reduction found in normotensives in this study is also important. Although relative risk of stroke and CHD in hypertensives is greater than in normotensives, the absolute number of deaths from these causes is greater in normotensive adults.[19
] Studies have observed that the greatest absolute number of strokes occurred in individuals with DBP between 80 and 89 mm Hg.[26
] The risk of stroke and CHD is directly related to the level of BP throughout the normotensive and hypertensive range.[27
] This intervention reduced the proportion of hypertensives in the study population from 7.8 to 4.5% and increased the prevalence of normotensives from 34 to 37%. Therefore, the significant BP reductions observed among both hypertensive and normotensive adults in this study have public health importance in the prevention of hypertension and CVD at the population level.
The main strength of this study was the ‘Intention-to-Treat’ analysis, which facilitated an understanding of the effectiveness of the intervention. Replication of similar interventions would be possible in community settings in developing countries, as the study was conducted with minimal resources. Use of pedometers to monitor exercise sessions was not possible in this study because of cost and logistic reasons. As it was not possible to include a control population, a pre-post intervention design was adopted within the available resources. The strategy to increase walking could have included a graduated increase in the physical activity program, to allow for behavioral conditioning of the subjects, but this would have posed difficulties in understanding the effect size attributed purely to the intervention. Longer periods of study would be necessary to record changes in measurements like waist circumference or BMI and to observe attrition patterns in participation behavior. In countries such as India where there are competing demands for limited resources, evaluation of public health interventions have to be tailor-made to reduce costs involved in research. In this study, a significant mean reduction of fasting blood sugar by 2.82 mg%, body weight by 0.17 kg, BMI by 0.06 kg / m2
, and a non-significant reduction of 0.04 cm in waist circumference were observed. This has to be interpreted in the light of the fact that higher exercise intensity is required to influence body weight and blood sugar (50 to 60 minutes per day on most days of the week).[6
Developed countries like Canada, Finland, New Zealand, Australia, US, and Denmark have implemented comprehensive strategies to address physical inactivity. Developing countries like Iran (Isfahan Healthy Heart Project) and Pakistan (Lodharan project) have initiated demonstration projects on the promotion of physical activity. India has initiated community projects like the Ballabgarh initiative and Chandigarh Healthy Heart project. The World Health Organization states that the important characteristics of the promotion of physical activity programs are: political commitment, integration in national policies, goal setting, funding, support from stakeholders, cultural sensitivity, inter-sectoral coordination, strong leadership, and workforce development.[29
] This is reflected in the National program for Prevention and Control of Diabetes, Cardiovascular Diseases, and Stroke,[30
] in India, which aims at health promotion through community interventions, by targeting physical activity and diet.
In conclusion, the functional feasibility of enabling people to undertake physical activity in the natural community and its effectiveness in significantly reducing the population's mean BP and blood sugar levels, in a low resource setting, have been proven by this study. Given the burden of Hypertension and CVD in India, there is an urgent need for community-based interventions, to socially market the concept of a physically active lifestyle. The findings of this study can help secure public support and an enabling environment for comprehensive community-based lifestyle interventions, even in developing countries.