Introduction: Non-communicable diseases have emerged among the prominent causes of preventable mortality and morbidity across the world. South Africa is currently dealing with a considerable burden of non-communicable diseases in addition to the burden of existing communicable diseases. Hypertension is among the top ten non-communicable diseases in the country. Non-communicable diseases are strongly associated and causally linked, to a large extent, to modifiable behavioural risk factors namely tobacco use, alcohol use, and physical inactivity as well as physiological risk factors such as obesity. With an increasingly aging population there is a need for more research on the incidence and associated risk factors of non-communicable diseases particularly among older adults aged 50 and over in the South African context.

Methods: This study utilized a mixed method design consisting of a quantitative and qualitative component. A cohort study design was used for the quantitative component which involved following the selected cohort from the baseline South African National Income Dynamics Study (NIDS) wave 1 in 2008 to wave 3 conducted 4 years later in 2012. An exploratory study design was used for the qualitative component.
The quantitative component of the study aimed to determine the incidence of hypertension in Wave 3 (2012) among individuals aged 50 and over in rural contexts in South Africa with no baseline hypertension in NIDS Wave 1 (2008) and to investigate the association between the selected modifiable behavioural and physiological risk factors including tobacco use, alcohol consumption, physical inactivity, and obesity. The baseline sample for this study consisted of 1460 adults aged 50 and over (mean age=63.2), who at baseline (2008) did not have hypertension, who developed hypertension by 2012, of whom there were n=309. The study also investigated the association of demographic and socioeconomic variables with the development of risk factors such as obesity and physical inactivity, and the initiation of smoking, and alcohol use between wave 1 and wave 3. The qualitative study aimed to explore individuals' perceptions of risk factors and disease. The qualitative sample consisted of 20 individuals aged 50 and over from a selected health care facility in a rural setting in South Africa.

Results: The hypertension incidence in the sample from the baseline wave 1 (2008) to follow up at wave 3 (2012) was 30.4% (CI 26.1%-35%). Multi-variable logistic regression revealed that those from the White, Indian and Coloured race group were 184% more likely to develop hypertension than those from the African race group between the two time periods. Individuals who were never married were 58% less likely to develop hypertension incidence than married individuals. Individuals who reported consuming alcohol less than three times a week were 60% less likely to develop hypertension, compared to those who reported never drinking alcohol suggesting a protective association. No significant relationships were found between the incidence of hypertension and physical inactivity, BMI and tobacco use in the multivariable analysis.
The study also investigated the association of demographic and socioeconomic variables with the development of risk factors such as obesity and physical inactivity, and the initiation of tobacco and alcohol use between Wave 1 and Wave 3. Significant findings showed that those with primary level education had a 43% reduced likelihood of developing obesity between the two time periods. For physical inactivity, females were 59% less likely to become physically inactive than males and with every year increase in age, there is a 2% reduced likelihood of incident physical inactivity. Those from the non-African race group were 90% more likely to report incident physical inactivity than the African race group. With tobacco use, with each year increase in age there is a 2% reduced likelihood of smoking incidence. Those from the non-African race group were 77% more likely to report tobacco use incidence than those from the African race group while females were 79% less likely than males to engage in this risk behaviour. Age and gender had significant results for alcohol consumption with a 3% reduced likelihood of reporting incident alcohol consumption in every year increase in age and females 51% less likely to report initiating alcohol use than males between the two time periods. The qualitative findings suggest that older respondents were aware of non-communicable diseases and generally recognised the impact that lifestyle factors have on health outcomes. Despite this, many admitted to not engaging in healthy lifestyle behaviour.

Conclusion: The findings of this study provide evidence that the rural older population is not spared from the burden of hypertension. In the four-year follow-up, 30% of individuals aged 50 and over, who were exposed to selected modifiable behavioural and physiological risk factors, had hypertension incidence. There is a need for continued research on the risk factors in South Africa as well as their association with the incidence of non-communicable diseases.