SPH-B postdoctoral fellow develops rigorous method to assess lifespan-healthspan dynamics

For physicians, extending the length of a patient’s life is not only a standard of practice; it is often an expectation. And when it comes to caring for patients of an advanced age, many practitioners confront the issue of morbidity (i.e., illness or problematic symptoms that affect quality of life). Until recently, the critical question

“As longevity increases, are we gaining healthier years or simply more years?” was unanswered—partly because there was no standard method for statistically combining longitudinal mortality and morbidity data in longevity research. According to Deependra Thapa, a postdoctoral fellow in the Indiana University School of Public Health-Bloomington (SPH-B) and primary author of recently published research, “This lack of statistical technique has hindered the progress in identifying interventions that effectively extend both lifespan and healthspan.”

This issue was at the forefront of Thapa’s mind as he and co-researchers published their findings in GeroScience, described as “the leading international journal focused on the biology of aging and the pathophysiology of age-related diseases.” The result of this research, “Life extending interventions do not necessarily result in compression of morbidity: a case example offering a robust statistical approach,” found no evidence that lifespan extension was accompanied by compression of morbidity. Rather, their research indicated a possible “expansion of morbidity… particularly for chronic caloric restriction.”

A keystone of their study is the development of the difference in rate effect method, referred to in the publication as DIRE. Through this novel analytical approach, which jointly analyzes mortality and morbidity data, Thapa offers a more robust framework for evaluating whether gains in lifespan are accompanied by proportional improvements in healthspan, and contributes to address a critical gap in aging research.

“We do not claim that lifespan-extending interventions categorically fail to compress morbidity,” the publication reads. “Rather, we illustrate here how a rigorous analytical approach can be applied to analyze the hypothesis of [compression of morbidity]. In the absence of robust standardized methods for evaluating this relationship, our approach provides a useful framework for future studies.”

Read more about SPH-B faculty, staff, and students making a difference at go.iu.edu/48bx.