A quantitative risk assessment for chronic traumatic encephalopathy (CTE) in football: How public health science evaluates evidence

How should science and policy interpret the recent finding that 110 of 111 former National Football League (NFL) players had brain pathology known as chronic traumatic encephalopathy (CTE) at autopsy? Some physicians view this (and related epidemiologic and mechanistic evidence) skeptically, emphasizing that the association between repeated head trauma (RHT) and CTE may be artifactual, that this “incidence” is biased by self-selection of players with cognitive or emotional symptoms, and that even if RHT causes CTE, the lesions themselves may be inconsequential. Public health scientists look at this emerging evidence quite differently; in particular, they tend not to fall prey to certain illogical arguments justifying inaction. We present a quantitative risk assessment showing that even accounting for the non-representativeness of the 110 cases, the risk of CTE in the NFL workforce amply meets both parts of the test for “a significant risk of material impairment of health” that would permit the U.S. Occupational Safety and Health Administration to intervene to reduce RHT exposure. We further conclude that according to available evidence, CTE is a public health problem, and that lawyers and physicians need to understand that this conclusion is based on standards of evidence at least as long-standing and robust as their own.     

Principal parts and morphological typology

Like the numbers in a sudoku puzzle, a lexeme’s principal parts provide enough information–but only enough–to deduce all of the remaining forms in its paradigm. Because principal parts are a distillation of the implicative relations that exist among the members of a lexeme’s paradigm, they afford an important (but heretofore neglected) basis for typological classification. We recognize three logically distinct sorts of principal-part systems that might be postulated for a given language: static, adaptive, and dynamic. Focussing for present purposes on dynamic systems, we propose five crosscutting criteria for the typological classification of principal-part systems. These criteria relate to (i) how many principal parts are needed to determine a lexeme’s paradigm; (ii) whether distinct lexemes possess parallel sets of principal parts; (iii) how many principal parts are needed to determine a given word in a lexeme’s paradigm; (iv) what sort of morphological relation exists between a principal part and the forms that it is used to deduce; and (v) whether lexemes’ nonprincipal parts are inferred from their principal parts in the same way from one inflection class to another. Drawing on these criteria, we propose a novel classification of a range of typologically diverse languages.