Heavy burden of non-communicable diseases at early age and gender disparities in an adult population of Burkina Faso: world health survey

The steady rise in non-communicable diseases (NCDs) worldwide is a key challenge on the global health agenda. Not only are chronic pathologies the leading cause of mortality globally, but they represent an increasing burden of morbidity and mortality in the developing world [1]. World Health Organization (WHO) estimates show that age-specific death rates from non-communicable diseases are already higher in sub-Saharan Africa (SSA) than in established market economies [2]. Moreover, overall mortality rates are higher in low- and middle-income countries (LMIC) than in high-income countries (HIC) [3].

NCDs increasingly take their toll in Western Africa in the form of cardiovascular diseases and pulmonary pathologies. The prevalence of asthma on the African continent has been estimated at 10.4% [3, 4], and a similar rate of 9.6% was observed in a population aged 15 to 64 years in the urban setting of Bobo-Dioulasso, Burkina Faso [5]. The prevalence of hypertension in an urban setting of Burkina Faso was estimated at 23% among adults aged 18 years or older [6]. The rise in NCDs has been attributed to rapid urbanization, sedentary lifestyles, global marketing of tobacco and food, and population aging [7]. In fact, economic growth, market integration, foreign direct investments and urbanization are driving long-term changes in mortality due to cardiovascular diseases and other NCDs, and their influence in LMICs is roughly three times stronger than that of population aging [8].

In spite of worldwide recognition that NCDs are a growing health problem that will hinder LMICs' social development and economic growth, few population-based studies are available to estimate their prevalence and distribution by age, gender, social group or urban/rural setting. In addition, while the literature clearly describes social differentials in health and presents conclusive and repeated evidence that the burden of illness falls disproportionately on women and the poor [9‐12], little is known about the scope of these inequalities with respect to NCDs, particularly in sub-Saharan Africa. Because women have less wealth, are more likely to be uneducated and have higher burdens of work [13, 14], all deriving from structures that shape gender and economic inequality, we can also expect to observe gender-related disparities, with higher prevalence of NCDs in women than in men. In fact, in 2004, the estimated proportional mortality from all NCDs in Burkina Faso was 24.7% for men and 27.6% for women [15]. Drawing upon data on Burkina Faso in the World Health Survey (WHS), a population-based household survey, our aim in this study was to describe the prevalence of NCD symptoms by age, gender, socioeconomic group and rural/urban setting, and to assess gender and socioeconomic differences in the prevalence of these symptoms.

Changing patterns in the causes of mortality and morbidity in low- and middle-income countries constitute one of the most important challenges on the global health agenda. Sub-Saharan Africa is doubly disadvantaged by the persistence of diseases of the pre-transition era--infectious disease conditions still account for two-thirds of deaths in sub-Saharan Africa [21] -- and the concurrent emergence of the heavy burden related to non-communicable diseases. This dual burden of disease [22‐24] is a considerable challenge to the countries' health systems. Our analyses show, first, that Burkina Faso, one of the poorest countries on the continent, is already facing the burden of NCDs. The overall prevalences of joint disease and back pain in our study were similar (16.2% [13.5; 19.2] and 24% [21.5; 26.6], respectively) to estimates reported in a comparative study on the prevalence of chronic pain conditions in developing countries [25]. The prevalence of asthma symptoms is also comparable (11.6% [9.5; 14.2]) to overall estimates for Africa [4] and to a previous study in Burkina Faso [5]. Finally, 17.9% [15.8; 20.2] of the adults who participated in the WHS reported angina pectoris-like symptoms; we did not find population estimates in the literature that would help correlate our results with comparable sub-Saharan populations. However, a previous study conducted in an urban setting in Burkina Faso found that the prevalence of hypertension, a known risk factor for angina pectoris, was about 23% among adults [6].

Our observations show a consistent relationship between age and the prevalence of NCD symptoms. However, the significance of this is paralleled by what appears, in terms of health conditions, to be evidence of early aging in the adult population. A markedly high prevalence for all studied conditions was present in young adults, suggesting early onset of NCDs and premature health decline in this population. Joint disease and back pain were unexpectedly high among the youngest, and their frequency increased steeply with age up to a prevalence of over 50% starting in the group aged 55-64 years. These observations converge with those of other studies suggesting that NCDs are both more lethal and developing at earlier ages in sub-Saharan Africa [2, 21, 26, 27]. For example, in a study by Baingana et al., half of cardiovascular disease deaths occurred among people 30 to 69 years of age, which is 10 or more years younger than in more developed regions [27]. Similar trends have been reported in Tanzania [2] and South Asia [28]. In India, 52% of cardiovascular deaths occur before the age of 70 years, whereas the rate in established market economies is only 23% [29]. Rheumatoid arthritis (RA) symptoms seem to occur nearly 10 years earlier in LMICs than in Caucasian populations in the United States and Europe [30, 31]. In a South African study, the prevalence of RA among adults 40 years old was significantly higher in native African populations than in people of European origin [31, 32]. Asthma in Africa is also more prevalent in adults younger than 40 years of age [4].

Age is the primary predictor of chronic illness survival, and aging explains the growth in prevalence of NCDs globally [7]. However, the aging process does not affect all the world's peoples in the same way [33]. The sources of the differential vulnerability of people living in resource-poor countries and the mechanisms that sustain it are still obscure. The lack of sufficient evidence is exacerbated by the facts that: 1) almost all studies on risk factors for NCDs--particularly cardiovascular diseases--have been carried out in developed countries; 2) it is uncertain to what extent the results of these studies can be directly generalized to the LMIC context [2, 24]; and 3) environmental factors could have a significant influence [2, 24]. Chronic stress, repeated exposure to infectious diseases and chronic inflammation caused by harsh living conditions might all play a key role in the premature aging of organs and body systems and, ultimately, in the incidence of NCDs [34].

In its recent report on NCDs, WHO [35] reported that poor and disadvantaged populations were more exposed globally to behavioural risks that lead to NCDs. Studies in Asia and Latin America, in particular, have demonstrated the existence of significant associations in LMICs between the prevalence of NCDs and socioeconomic status, especially level of education [35‐40]. These associations were not seen in our study in Burkina Faso; education did not appear to have a protective effect on NCDs symptoms, and no pattern emerged from the study of any reported prevalence by income level. In fact, these results are not really surprising in the particular context of Burkina Faso, a sub-Saharan African country with a double burden [2, 41, 42] of infectious and chronic diseases. In many SSA countries, health inequality remains anchored in social inequality, but is caused also by changes in lifestyles and diet in all social classes [43], particularly among residents of cities and members of advantaged groups. NCDs are thus the product of a complex combination of forces and determinants, and they affect, depending on the circumstances, both disadvantaged and more advantaged classes. This explains the contradictory results reported by studies examining the relationship, in SSA, between socioeconomic status and the presence of NCDs or of their risk factors, such as obesity, hypertension, or metabolic syndrome. Some have reported greater exposure to risk and higher prevalence of NCDs among the poor [35, 44, 45], while others have reported more pronounced vulnerability among the elite, the middle classes, and city residents [45‐49]. WHO and the research community have highlighted the need for more research to better understand the complex interrelationship between NCDs and socioeconomic status [35, 43]. There is also evidence that NCDs take a heavier toll on women than on men, and that in this area as in others, women are considerably more exposed to illness and have worse prognoses [28]. It has been suggested that the incidence of chronic diseases in old age is related to life course adversities [50]. Because of their social disadvantage and differential exposure to risk factors [51‐53], women are apt to accumulate life course socioeconomic adversities that will be translated into adverse health outcomes. Our observations tend to support the idea that women are subject to greater differential vulnerability than men in terms of NCDs. Gender differences were quite large and significant in our study. Women more often reported symptoms of all four conditions. Differences did not disappear after adjustment for socioeconomic characteristics. When gender and occupation were considered jointly, housewives and unemployed women systematically and significantly remained the group with the highest prevalence rates.

None of the Millennium Development Goals make reference to NCDs. Because of this oversight, governments and the international community have paid little attention to major issues in transforming the post-transition morbidity profiles of African societies. However, these morbidity profiles can be assessed at the population level through the World Health Surveys, from which the amplitude of NCD symptoms can be appreciated. Our work suggests that social inequality extends into the distribution of NCDs among social groups, and supports the thesis of a differential vulnerability in Burkinabè women. It raises the disturbing possibility of an abnormally high rate of premature morbidity that could manifest as a form of premature aging in the adult population. Finally, our work supports the need for sustained commitment to research on population issues related to NCDs in resource-poor countries. The economic and health-related stakes, in terms of both chronic illnesses in general and their premature occurrence in particular, are potentially very high. We believe it is essential, with the help of large population studies, to characterize the distribution of NCDs more precisely across all social and age gradients. Second, more research is necessary to uncover the gender features and understand the sources of women's differential vulnerability to chronic diseases. Third, the question of the alleged premature aging should be at the centre of this research agenda. We need to understand the processes that control the aging of social groups and the underlying causes of the vulnerability of people living in LMICs, and especially the differential vulnerability of specific groups. Finally, health policies should be informed by an estimate of the social burden caused by premature morbidity and its effects on healthcare systems that are struggling to meet their populations' basic needs and are already very fragile.