Platelet activation plays an important role in hemostasis through its participation in preventing excessive bleeding. [1] On the other hand, platelet activation may also lead to arterial thrombosis, an essential element for several cerebrovascular diseases. [2] While the extent of platelet activation and reactivity can be measured using various laboratory tests, such tests are not routinely performed. Modern hematology analyzers are routinely used for complete blood count, a commonly performed blood test, and report platelet indices that are associated with heightened platelet activation. [3,4] These platelet indices are potentially useful markers for early diagnosis of cardiovascular diseases such as myocardial infarction and stroke. Platelet distribution width (PDW) is one of the platelet indices and indicates the heterogeneity in circulating platelet sizes. [5] Increased variation in platelet sizes, hence elevated PDW, may result from low-grade ongoing platelet activation; platelet activation is associated with morphologic changes in platelets. [4,6] PDW has a heritability of 37%, suggesting that high PDW levels may have long-term effects on human health. [7]

PDW is associated with a wide variety of morbidities and mortality in several studies. For example, PDW is associated with increased mortality in a wide variety of patient subpopulations, such as those with heart failure, coronary artery disease, or stroke. [[8], [9], [10], [11], [12]] PDW is also associated with poor prognosis after heart failure, stroke, or myocardial infarction. [[13], [14], [15], [16]] On the other hand, some studies have found no relationship between PDW and mortality after myocardial infarction, stroke, or heart failure. [[17], [18], [19], [20]] These disparate results may stem from the limitations of these studies; many of these studies had small sample sizes, enrolled specific subpopulations, or were focused on hospitalized patients. To mitigate these limitations, we examined the relationship between PDW and all-cause and cause-specific mortality in a large cohort representative of the United States population.