Osuntokun Award Lecture 2021: Challenges of Measuring the Burden of Stroke in Africa.

BACKGROUND

Over recent years non-communicable diseases have dramatically increased in low- and middle-income countries, including those of sub-Saharan Africa. With continuing high levels of infectious disease, these countries now face the double burden of disease. Stroke has emerged as a major cause of hospital admission, disability, and mortality for which the major modifiable risk factor is hypertension, which is often not diagnosed and, even if diagnosed, not treated and, even if treated, not controlled.

METHODS

In this award lecture paper I outline my personal experience of measuring the burden of, and risk factors for, stroke in sub-Saharan Africa, along with the challenges faced. I will specifically describe the measurement of mortality and case fatality, prevalence and incidence as well as commenting on aetiology and risk factors and reflect on future initiatives and directions.

RESULTS

Over the past 5 decades there has been a dramatic increase in numbers of stroke patients admitted to hospital throughout sub-Saharan Africa, with high in hospital mortality rates, also reflected in high case fatality rates in those cohorts followed up following discharge from hospital. Community-based surveys assessing mortality from stroke using verbal autopsy have demonstrated very high age-adjusted rates. Age adjusted prevalence rates assessed by door-to-door surveys have generally shown lower prevalence than high income countries. The Tanzanian stroke incidence study, which incorporated verbal autopsy for those patients dying before reaching hospital, demonstrated some of the highest age-adjusted stroke incidence rates in the world. There were high rates of stroke in younger ages and high rates of intracranial haemorrhage though not as high as previously shown in hospital-based studies. Hypertension is the main modifiable risk factor but other risk factors such as HIV are important while, certainly in rural populations, raised cholesterol remains rare as does carotid artery stenosis and history of transient ischemic attack. Other vascular disease such as ischemic heart disease and peripheral vascular disease is also less common.

CONCLUSIONS

There is already a large burden relating to stroke in sub-Saharan Africa and this will only escalate further as the population ages. Hypertension is the biggest risk factor for mortality worldwide and in sub-Saharan Africa prevalence rates are very high with the majority of people suffering with stroke not being diagnosed with their hypertension prior to their stroke. The most important challenge is to improve primary prevention for which improving diagnosis and control rates for hypertension is the number one priority. For those who do have stroke there is a need to increase the number of suitably staffed stroke units as these have been shown to have a very large impact on improving both mortality and morbidity in high income countries. There are still many unanswered questions and a need for more research throughout sub-Saharan Africa on risk factors, and treatment, for stroke.