The Prevalence of Chronic Pain in Developing Countries

It is often reported that the prevalence of self-reported chronic pain in the adult general population is approximately 20% in developed countries. All ages are affected, with women and the elderly being over-represented [1]. However, there have been few population-based surveys conducted in developing countries, defined by the World Bank as “a country that has a relatively low standard of living, an undeveloped industrial base and a moderate-to-low Human Development Index (HDI) score and per capita income” [101].

It could be argued that the prevalence of chronic pain would be higher in the developed world since individuals live longer and women have more access to health services. Alternatively, the prevalence of chronic pain may be higher in developing countries owing to a higher incidence of pain-related trauma from road traffic and industrial accidents, and a higher prevalence of pain-related diseases, such as diabetes, HIV/AIDS and cancer. Evidence suggests that common barriers to effective pain management in developing countries include the low priority given to pain management by government agencies, a lack of education in pain management, restriction of drug availability as a result of cost implications, poor patient compliance and a fear of addiction in relation to opioids [102]. Furthermore, the tendency for healthcare professionals in developing countries to focus on treating diseases causing pain, rather than relieving pain itself, may contribute to inadequate pain management [2]. Whether inadequate pain management affects prevalence is not known.

Interestingly, there is a lack of reliable statistics on the magnitude of chronic pain in developed and developing countries, making economic planning difficult. The majority of population-based surveys estimating the prevalence of chronic pain have been conducted by nongovernmental research programs, suggesting that governments do not consider epidemiological data on pain as a public health priority. An analysis of information provided by 19 member countries of the International Association for the Study of Pain found that only three countries (USA, UK and Portugal) used governmental epidemiological research on pain when developing national law, regulations or statutes, with epidemiological research by nongovernmental organizations used in only two other countries (Canada and Australia) [103]. In addition, most epidemiological research is funded by the developed world and favors studies on and investigating teams from affluent countries, resulting in larger sample population sizes. By contrast, studies estimating prevalence in developing countries are rare and tend to be part of multinational surveys.

In 2008, Smith and Torrance [3] estimated the mean worldwide prevalence as 22.9% (95% CI: 22.7–23.2%; range: 5.5% for Nigeria to 33% for Chile [4]). Recently, our team conducted a systematic review and found large variations in estimates of the prevalence of chronic pain within and between studies, countries and regions [5]. We estimated weighted mean ± standard deviation prevalence of chronic pain worldwide as 30.3 ± 11.7% (19 studies, 65 surveys, 34 countries, 182,019 respondents), although removal of a large study that may have included a sample of individuals with comorbidities reduced the estimate to 28.0 ± 11.8% (47 surveys, 33 countries and 139,770 participants) [6]. In our analysis, we also estimated the prevalence of chronic pain in countries with a HDI <0.9. The HDI is used to measure the impact of economic policies on quality of life. Countries with HDIs ≥0.9 are classified as developed and those with HDIs <0.9 as developing [104]. The HDI is calculated by averaging three indices that reflect health and longevity (measured by life expectancy at birth), education (measured by adult literacy, and enrollment into primary, secondary and tertiary education establishments) and living standards (measured by gross domestic product per capita. In our analysis, there was no correlation between HDI and prevalence. In countries with a HDI <0.9, prevalence was 33.9 ± 14.5% (three studies, 15 surveys, 12 countries and 25,843 respondents) and higher than prevalence in countries with a HDI of ≥0.9, which was 29.9 ± 12.7% (19 studies, 50 surveys, 22 countries and 156,176 respondents). We did not find any study reports that focused on a country with a HDI <0.9 on its own. Consequently, the data set for countries with HDIs <0.9 was dominated by three large epidemiological surveys that estimated the prevalence of chronic pain using sample populations from developed and developing countries [4,6,7]. Gureje et al. found that the prevalence of chronic pain ranged from 11.8 (Nagasaki, Japan) to 32.8% (Berlin, Germany) in developed countries and from 5.5 (Abadan, Nigeria) to 33.0% (Santiago, Chile) in developing countries [4]. Tsang et al. found that pain prevalence ranged from 38.4 to 49.6% in developed countries and from 24.1 to 60.4% in developing countries [6]. Breivik et al. found that prevalence ranged from 12 (Spain) to 30% (Norway) in developed countries and was 27% in Poland, the only country with a HDI <0.9 included in the study [7]. We concluded that there was insufficient reliable data to estimate the prevalence of chronic pain in countries with a HDI <0.9 with any certainty. Variability in estimates between surveys was a major concern.

It is likely that the determinants of chronic pain will differ between developing and developed countries, with a probability that the prevalence of neuropathic pain will be higher in developing countries owing to the predominance of etiologies that damage the somatosensory nervous system. Expert panels have suggested that neuropathic pain is underdiagnosed and undertreated in the Middle East [8] and Asia Pacific [9]. Furthermore, differences in prevalence between developed and developing countries may be exacerbated when comparing urban and rural populations. In 1997, Volinn conducted a criteria-based review that found that the prevalence of low back pain in the general populations of high-income countries was higher than the prevalence of rural-based populations of low-income countries [10]. Prevalence rates were two- to four-times higher in the general population in Belgium, Germany and Sweden than in farmers from the Philippines, Indonesia, Nigeria and southern China. Rates were also higher in urban populations of low-income countries than rural populations. More recently, a descriptive overview of 26 articles by Mousavi et al. suggested that the prevalence of low back pain in Iran ranged from 14.4 to 84.1% [11]. The incidence of disabling low back pain was 2.1%, which would be the third principal cause of disease in the general population of Iran.

The impact and burden of chronic pain on individuals and societies appear to be similar across the world, although most evidence to date has been gathered from North America, Europe and Australia, with limited data obtained from resource-limited countries. A recent study on individuals with cancer in Saudi Arabia found that the impact of chronic pain on the patients‘ life is similar to that in the developed world, although subtle cultural differences may present [12]. Pain-coping strategies adopted by individuals from Saudi Arabia were focused on spiritual- and cultural-based beliefs in God. A comparison of cancer patients from Iran found that there were higher levels of depressive symptoms, lower self-esteem, impaired emotional functioning and lower scores on global quality of life in individuals experiencing pain than those that did not [13]. There is a lack of data on the economic impact of chronic pain in countries with a HDI <0.9; however, a recent study in Morocco found that the average medical cost of diagnosis, treatment and 1-year follow-up of a lung cancer patient was US$4600 [14].

Clearly, there is a need for epidemiological studies that estimate the prevalence of chronic pain in developing countries to determine the scale of the problem. The large amount of heterogeneity in published surveys due to differences in methodologies, characteristics of target population and categorization of chronic pain hinders attempts to pool data. Often, surveys estimating the prevalence of chronic pain are not culturally sensitive and use survey tools developed in English-speaking countries. Our research on pain in the Arabic Middle East and North Africa demonstrates that it is possible to undertake population-based surveys relatively inexpensively using partnerships with investigators in developing and developed countries. Critical to our research has been the need to translate and linguistically validate commonly used survey tools into local languages so that they are fit for purpose in target populations [15,16]. Only by conducting more epidemiological studies in the developing world will we be able to fully understand the determinants and distribution of chronic pain worldwide.

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.