Global burden of physical inactivity

Guidelines on the total volume of physical activity required to reduce the risk of specific NCDs are imprecise; however, the WHO recommends that adults undertake at least 150 min of moderate-intensity physical activity per week, or 75 min of vigorous-intensity physical activity per week, to reduce the overall risk of NCDs.1 Worldwide 23.3% of adults do not meet these recommendations and are considered physically inactive.2 Low physical activity was identified as one of the leading risk factors responsible for the global disease burden, with an estimated 1.4 million deaths attributed to low physical activity in 2016, an increase of 18.4% since 2006.5 The disease burden is especially high in LMICs, with 75% of the estimated 13.4 million disability-adjusted life years lost to physical inactivity in 2013 attributed to these regions.6 In the same year, physical inactivity was estimated to have cost global healthcare systems international $ 53.8 billion.6

Burden of physical inactivity in Africa

Africa is a region in transition. The demographic profile of the continent is changing: reductions in infant and child mortality have contributed to rapid population growth and a concomitant rise in life expectancy. Africa is also the fastest urbanising continent, with the number of people living in urban areas projected to triple in the next 50 years.7 Globalisation, technological advances and economic development have all contributed to a trend towards sedentary lifestyles and the uptake of unhealthy behaviours on the continent. These demographic, social and environmental changes have led to an emerging NCD epidemic, complicated by an existing high prevalence and incidence of chronic infectious diseases such as tuberculosis, malaria and HIV. Physical activity is influenced by a complex interaction of biological, social and environmental factors. As such, the distribution and determinants of physical inactivity, and its relative contribution to the burden of NCDs, will likely differ within and between African countries at varying stages of economic development and with diverse sociocultural contexts. A meta-analysis of self-reported physical activity data from 22 African countries found 16% of men and 24% of women were physically inactive, which is comparable to prevalences reported in HICs.8 However, the prevalence of physical inactivity varied between countries, ranging from 46.2% of men and 60.3% of women in Mali to 3.8% of men and 4.2% of women in Mozambique.8 The source of this variation is not well understood, but differences in body mass index, perceptions of body image, socioeconomic status, urbanicity, safety, security and access to spaces that support physical activity are likely to be contributing factors.9–15

Improving our evidence base through the objective measurement of physical activity

The limitations of self-report data currently restrict our ability to accurately characterise the dose–response relationship between physical activity and disease risk in these populations. Meanwhile, the technology of objective measurement devices is constantly evolving: manufacturers are continually refining device algorithms to improve activity pattern recognition, increasing our ability to delineate the health benefits of specific activities.9 Our knowledge of the social, biological and environmental determinants of physical activity in Africa, including the impact of urbanisation and economic development, is limited by the need for context-specific measures for these determinants and the paucity of longitudinal data to determine causation.21 Smart phone ownership in Africa is accelerating: a median of 33% reported owning a smart phone in 2018, with a 14%–15% increase in ownership reported in Senegal, South Africa and Ghana between 2015 and 2017.22 This and the increasing availability of commercial physical activity monitors presents an opportunity to harness physical activity data collected as users carry out their daily lives.22 With careful consideration of ethical, data privacy and security issues, these devices have the potential to facilitate routine surveillance and monitoring of population physical activity patterns and trends, as well as evaluating clinical, societal and environmental interventions at the individual and population level.

Opportunity for intervention

The majority of African countries have a policy or strategy which addresses physical inactivity, but only 70% report that these are operational,23 and evidence of effectiveness is scarce, partly due to the limited surveillance of physical activity across the continent. Integrating active living and sports programmes within schools and work places is a strategy advocated by global policy makers and a recommended ‘best buy’ intervention for the prevention and control of the global NCD pandemic.24 Likewise, creating environments which support the integration of physical activity into people’s daily lives through active travel or leisure activity is highly recommended.25 However, evidence of effective and sustainable interventions to increase physical activity at the population level within these settings is limited. Furthermore, the observed benefits of such interventions may not transfer directly to the African context. The unprecedented, and often uncontrolled, growth in urbanisation on the continent calls for urgent and innovative urban planning policies that support an active population.

Using context-specific data on population activity levels and their social and environmental determinants in the design and implementation of policies ensures they address the specific needs of populations in these regions. Similarly, integrating objective measurement of physical activity patterns and trends within research and surveillance infrastructure will be integral to improving the evidence base for policy development and the effective evaluation of these interventions at the population level. The success of such interventions will likely require engagement with education, commercial, urban planning, transportation, environmental and sports and recreation sectors. Consideration of individual-level factors such as wearer compliance and participation, as well as broader environmental issues such as climate, geography, safety and security will be necessary for the long-term sustainability of these interventions.9 12 20 21 25 Capacity building initiatives and financial support will also be integral to the widespread deployment of objective measurement devices. Finally, physical activity interventions should be integrated within a broader NCD prevention strategy addressing NCD risk factors such as diet, smoking and alcohol consumption.