Abstract
Leo Tolstoy's novel Anna Karenina starts with the famous line, “All happy families are alike; each unhappy family is unhappy in its own way.” This “Anna Karenina Principle” has been applied in numerous contexts, including ecological risk assessment, microbiomes, economics, and many others. In physiology and health, we might rephrase it as a hypothesis; “All healthy physiologies are healthy in relatively standard ways, but there are limitless ways in which physiology can go awry.” This hypothesis raises interesting corollaries: to what extent is there a general, unique profile of physiological “health,” which might be perturbed in a multiplicity of ways? Can we understand health as the body's ability to maintain such a homeostatic state, or more broadly its dynamic equilibrium? Might having an overall profile that is far from average be an indicator either of a specific but undiagnosed pathology, or of a general lack of resiliency predisposing the individual to higher risks of a host of adverse outcomes?
Highlights
Leo Tolstoy’s novel Anna Karenina starts with the famous line, “All happy families are alike; each unhappy family is unhappy in its own way.”. This “Anna Karenina Principle” has been applied in numerous contexts, including ecological risk assessment, microbiomes, economics, and many others. We might rephrase it as a hypothesis; “All healthy physiologies are healthy in relatively standard ways, but there are limitless ways in which physiology can go awry.”
This hypothesis raises interesting corollaries: to what extent is there a general, unique profile of physiological “health,” which might be perturbed in a multiplicity of ways? Can we understand health as the body’s ability to maintain such a homeostatic state, or more broadly its dynamic equilibrium? Might having an overall profile that is far from average be an indicator either of a specific but undiagnosed pathology, or of a general lack of resiliency predisposing the individual to higher risks of a host of adverse outcomes?
One way to operationalize the Anna Karenina Principle and tackle such questions is via the Mahalanobis distance (MD), a measure that assesses how unusual a multivariate profile is, taking into account known correlations among the variables [1]
Summary
Leo Tolstoy’s novel Anna Karenina starts with the famous line, “All happy families are alike; each unhappy family is unhappy in its own way.” This “Anna Karenina Principle” has been applied in numerous contexts, including ecological risk assessment, microbiomes, economics, and many others. Might having an overall profile that is far from average be an indicator either of a specific but undiagnosed pathology, or of a general lack of resiliency predisposing the individual to higher risks of a host of adverse outcomes?
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