title: Extended Twilight among Isogenic C. elegans Causes a Disproportionate Scaling between Lifespan and Health.
abstract: Although many genetic factors and lifestyle interventions are known to affect the mean lifespan of animal populations, the physiological variation displayed by individuals across their lifespans remains largely uncharacterized. Here, we use a custom culture apparatus to continuously monitor five aspects of aging physiology across hundreds of isolated Caenorhabditis elegans individuals kept in a constant environment from hatching until death. Aggregating these measurements into an overall estimate of senescence, we find two chief differences between longer- and shorter-lived individuals. First, though long- and short-lived individuals are physiologically equivalent in early adulthood, longer-lived individuals experience a lower rate of physiological decline throughout life. Second, and counter-intuitively, long-lived individuals have a disproportionately extended "twilight" period of low physiological function. While longer-lived individuals experience more overall days of good health, their proportion of good to bad health, and thus their average quality of life, is systematically lower than that of shorter-lived individuals. We conclude that, within a homogeneous population reared under constant conditions, the period of early-life good health is comparatively uniform, and the most plastic period in the aging process is end-of-life senescence.
authors.affiliation: Department of Genetics, Washington University in St. Louis, St. Louis, MO 63110, USA; Department of Developmental Biology, Washington University in St. Louis, St. Louis, MO 63110, USA.
authors.forename: William B
authors.initials: WB
authors.lastname: Zhang
authors.affiliation: Department of Genetics, Washington University in St. Louis, St. Louis, MO 63110, USA; Department of Developmental Biology, Washington University in St. Louis, St. Louis, MO 63110, USA; Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA.
authors.forename: Drew B
authors.initials: DB
authors.lastname: Sinha
authors.affiliation: Department of Genetics, Washington University in St. Louis, St. Louis, MO 63110, USA; Department of Developmental Biology, Washington University in St. Louis, St. Louis, MO 63110, USA; Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA.
authors.forename: William E
authors.initials: WE
authors.lastname: Pittman
authors.affiliation: Department of Genetics, Washington University in St. Louis, St. Louis, MO 63110, USA; Department of Developmental Biology, Washington University in St. Louis, St. Louis, MO 63110, USA.
authors.forename: Erik
authors.initials: E
authors.lastname: Hvatum
authors.affiliation: Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Stroustrup
authors.affiliation: Department of Genetics, Washington University in St. Louis, St. Louis, MO 63110, USA; Department of Developmental Biology, Washington University in St. Louis, St. Louis, MO 63110, USA. Electronic address: zpincus@wustl.edu.
authors.forename: Zachary
authors.initials: Z
authors.lastname: Pincus
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans; D011788:Quality of Life
keywords: Caenorhabditis elegans; health; healthspan; inter-individual variation; lifespan; rate of aging