Background and methods 

Platelets are key cells in coagulation and inflammation andas such play an important role in the development of ischemic cardiovascular diseases(CVD) such as myocardial infarction and ischemic stroke. Stroke is a leading cause ofdeath in Sub-Saharan Africa (SSA). The incidences of CVD are rising due to lifestyle changesaffected partly by global urbanization. To date, no data are available on determinants ofplatelet activation and reactivity in populations in SSA. The aim of our study was to studyenvironmental and non-genetic host determinants of platelet reactivity in a cohort of319 healthy Tanzanian adults with a special focus on differences between those living inurban or rural areas. In addition, we studied the associations of platelet parameters withcirculating inflammatory markers and cytokine production capacity.

Results 

While measures of platelet activation/reactivity were similar between urban and rural subpopulations, their associations with both host and environmental factorsshowed distinct patterns between urban and rural subpopulations. Only in the urbanpopulation, platelet activation/reactivity was associated with traditional risk factorsfor CVD including advanced age, high systolic blood pressure, alcohol use and smokingof tobacco. Other factors associated with platelet activation/reactivity were use of pitlatrine or smoke emitting cooking fuel. Important differences between urban and ruralsubpopulations were also found in associations of platelet reactivity with inflammatorymarkers: platelet reactivity correlated positively with plasma levels of alpha-1-antitrypsin(AAT) and negatively with interleukin (IL)-1β and IL-18 levels in the urban but not in therural subpopulation, whereas only in the rural subpopulation platelet reactivity wasstrongly correlated with IL-1Ra and IL-18BPa levels. In addition, platelet numbers wereinversely associated with whole blood cytokine production capacity in general, whereasplatelet activation had predominantly negative correlations with TNFα production in therural subpopulation.

Conclusion 

Associations between platelet reactivity with environmental and non-genetichost factors and plasma inflammatory markers differ between individuals from healthyrural and urban subpopulations in Tanzania. These differences provide novel insights inthe possible health consequences of urbanization and lifestyle changes in SSA.