Perceived anthropomorphism of AI and belongingness need: the sequential roles of liking and perceived emotional support.

The substantial global increase in human life expectancy—a major public health achievement—has sparked significant academic and policy debate regarding the “lifespan-healthspan” dynamic (; ). At the core of this discourse is whether older adults are living longer, healthier lives, or merely enduring extended periods of illness and disability. Three competing paradigms address this question. The “compression of morbidity” hypothesis posits that lifestyle modifications and medical advances delay the onset of chronic illness, compressing the period of infirmity into a shorter interval near the end of life (, ). Conversely, the “expansion of morbidity” (or “failures of success”) perspective argues that medical technologies—particularly those controlling fatal complications—inadvertently prolong the duration of chronic diseases and disability (). Proposing a middle ground, the “dynamic equilibrium” theory suggests that while the prevalence of chronic conditions may rise with increased survival, their severity diminishes, maintaining a relatively stable overall functional status (). Decades of empirical research have yielded mixed results, indicating that these paradigms are not mutually exclusive but rather domain-specific and highly contextualized (). Globally, recent comprehensive analyses reveal that gains in life expectancy have outpaced improvements in health-adjusted life expectancy. This suggests a general expansion of morbidity driven by the rising prevalence of chronic conditions and behavioral risk factors (; ). Meanwhile, the overall global disease burden remains highly concentrated in older populations (). However, this overarching trend masks divergent patterns across specific nations and health domains. In the United States, researchers have documented a pronounced expansion of disease alongside a clear deterioration in mobility functioning (). Although some long-term improvements in disability-free life expectancy at older ages have been observed (), recent cohort studies reveal marked reversals. Younger cohorts, such as the Baby Boomers, are experiencing a pronounced expansion of morbidity, while disability trends remain generally stable—aligning with dynamic equilibrium—or only expand among socioeconomically disadvantaged subgroups (; ). Furthermore, these recent cohorts exhibit worsening physiological and mental health profiles (). European evidence, by contrast, presents a differing trajectory. Danish studies, for instance, demonstrate a “success of success” effect, where later-born cohorts of nonagenarians exhibit significantly better cognitive functioning and abilities in daily living, though objective physical performance showed no consistent improvement compared to their predecessors born a decade earlier (, ). Similarly, longitudinal data from the Netherlands highlight a distinct domain divergence: a substantial decline in physically healthy life expectancy occurring simultaneously with a marked increase in cognitively healthy life expectancy ().