The remarkable increase in life expectancy observed across most high-income countries has sparked growing concern about whether additional years of life are accompanied by good health or by increasing levels of disability and dependence. To address this issue, public health research has focused on indicators such as disability-free life expectancy (DFLE), which estimate not only how long people live, but also how many of those years are lived without significant functional limitations [1–3]. These metrics are essential for understanding the evolving needs of aging populations and for anticipating future demands on health and long-term care systems. In this context, analyzing long-term trends in disability and dependence at the national level provides valuable insights into the sustainability of care models and the equity of support systems, particularly in societies facing rapid demographic aging.

In public health, disability is typically understood through the International Classification of Functioning, Disability and Health (ICF), which defines it as a result of impairments, activity limitations, and participation restrictions caused by the interaction between health conditions and contextual factors [4]. Dependence, in turn, refers to the need for personal assistance or technical aids to perform basic or instrumental activities of daily living. These concepts are particularly relevant in aging societies, where the distribution and severity of disability have direct implications for long-term care needs [5].

While international indicators such as Healthy Life Years (HLY) are widely used for cross-country comparisons, they are based on a single self-reported item and do not distinguish the severity or functional impact of limitations. [3]. Spain regularly contributes to these international datasets, yet such harmonized metrics may overlook national specificities in the distribution and intensity of disability. As a result, complementary national-level analyses remain essential for understanding population needs, especially in contexts where care systems are under pressure and long-term planning depends on accurate projections of dependency and support requirements.

Since the 1980s, several theoretical models have emerged to explain how gains in longevity might relate to trends in disability. Gruenberg’s “failures of success” hypothesis argued that medical advances had reduced mortality without preventing the onset of chronic or disabling conditions, thereby extending years lived with disability [6]. Fries’ compression of morbidity theory suggested the opposite—that better health behaviors and preventive care could delay the onset of disability, compressing it into the final years of life [7]. Manton’s dynamic equilibrium model offered a middle ground, where disease prevalence may remain stable or rise, but with a shift toward milder forms of disability [8].

Empirical evidence has since revealed heterogeneous patterns. While some countries have reported compression of disability, others have seen expansion, or shifting thresholds between mild, severe, and dependent states [9, 10]. These divergences reflect not only epidemiological differences (e.g., morbidity profiles, health behaviors), but they also have important implications for care provision. In Southern European countries, including Spain, where a familialist model of care predominates and informal caregiving by family members—especially women—remains central [11], rising disability prevalence may put additional pressure on households. This pressure is further compounded by demographic and social changes, such as population aging, declining fertility, rising female labor force participation, and the growth of single-person households [12].

Spain, despite having one of the highest life expectancies globally, has limited long-term evidence on national trends in disability, particularly regarding severity and dependence. Earlier research has documented both increases in chronic conditions [13, 14] and signs of compression in functional limitations [15, 16], but often with methodological or geographic limitations. Moreover, little is known about how the burden of disability has evolved by age, sex, and intensity of limitation over the past three decades.

Understanding these trends is essential for anticipating care demands and evaluating the sustainability of current models of provision. While the majority of dependent older adults in Spain still rely on family members for support, recent evidence points to a slow but growing shift toward defamilialization, particularly among the oldest age groups [17, 18]. Mapping the evolution of disability, severe disability, and dependence is therefore not only an epidemiological task, but also one with major implications for care systems and policy planning.

This study examines trends in total and disability-free life expectancy, as well as in years lived with severe disability, and with dependence, in Spain between 1986 and 2020. Drawing on four waves of nationally representative disability surveys and applying the Sullivan method, we analyze how these indicators have evolved over time by age and sex. Spain represents a particularly relevant case for studying these dynamics, as it combines one of the highest life expectancies in the world with a traditionally family-based model of care provision. While not aiming to compare countries directly, our findings contribute to broader public health discussions on aging, disability, and care, offering insights that may inform policy responses in other aging societies where informal caregiving continues to play a central role.

This study used microdata from four cross-sectional disability surveys conducted in Spain in 1986, 1999, 2008, and 2020: the Encuesta sobre Discapacidades, Deficiencias y Minusvalías [19], the Encuesta sobre Discapacidades, Deficiencias y Estado de Salud [20], and the Encuesta sobre Discapacidad, Autonomía personal y Situaciones de Dependencia [21, 22]. All four surveys were designed and carried out by the Spanish National Statistics Institute (INE) to estimate the prevalence and severity of disability in the population aged 6 years and older living in private households. The core samples excluded institutionalized individuals, although supplementary institutional samples were collected in 2008 and 2020. To ensure comparability across the entire 1986–2020 period, these supplementary samples were not included in our analysis. Each survey used probabilistic, stratified sampling methods to ensure national representativeness.

A clear demographic shift is observed in the Spanish population, with the largest age group moving progressively from ages 10–14 in 1986 to 40–44 in 2020. The proportion of the population in older age groups has also increased substantially over time (Supplementary Figure S1). At the same time, the distribution of disability by age and sex shows parallel changes across the study period.

In relative terms, disability rates consistently rise with age in both men and women across all periods. However, changes in population age structure have also resulted in notable shifts in the structure of disability. In 1986, the highest number of people with disabilities was found in the 60–64 age group for men and 70–74 for women. By 1999, this shifted to the 75–79 group for both sexes. In 2008, the peak remained at 75–79 for men but rose to 80–84 for women. Finally, in 2020, the highest number of people with disabilities was observed in the 80–84 age group for men and 85–89 for women.

This study offers the most comprehensive long-term analysis to date of trends in disability and dependence in Spain, drawing on nationally representative data collected between 1986 and 2020. Over this period, both life expectancy (LE) and disability-free life expectancy (DFLE) increased across all age groups, although not in all subperiods. However, the absolute number of years lived with disability—particularly in its severe and dependent forms—also rose. These findings support the concept of an incomplete compression of morbidity, where gains in healthy life years are not fully offset by reductions in time lived with disability [7, 26].

The observed disability trends are consistent with those reported in earlier periods [15, 16, 27], confirming that the trajectory of DFLE gains, coupled with rising years with disability, has continued into the last decade. This pattern partially aligns with the hypothesis of disability compression proposed by Fries in 1980, which anticipated a decline in disability relative to overall life expectancy [7]. Similar dynamics have been documented in other high-income countries such as Sweden [28, 29], Norway [30], Denmark [31], and the United Kingdoms [32].

One particularly persistent pattern is the gender gap in disability [33], Women consistently exhibit longer life expectancy and longer DFLE than men, but they also live more years with disability. This gap has remained stable in Spain over the study period. The disparity has been attributed to biological factors, historical differences in smoking behaviors, social and economic inequalities, and gender-specific prevalence of disabling and fatal conditions [34, 35]. In the Spanish context, a considerable portion of the sex difference in disability prevalence is explained by higher rates of musculoskeletal disorders among women, notably osteoporosis and osteoarthritis [36]. A relevant hypothesis for future research concerns the long-term effect of smoking uptake among Spanish women since the 1980s [37], and whether this will shift sex patterns in disability over time.

A notable contribution of this study is the observation of an increase in severe disability among older adults, a trend consistent with findings from several high-income countries, particularly in Scandinavia [28, 30, 31]. These results suggest that while some compression of disability may be occurring, it is likely concentrated in milder forms of functional limitation. In contrast, severe disability appears to be expanding, especially in advanced age. This pattern contrasts with Manton’s dynamic equilibrium hypothesis [8], which posits that increased longevity is associated with a shift toward less severe forms of morbidity. Our findings, however, indicate that this equilibrium may not extend to the most disabling conditions. Increases in severe disability among younger age groups appear to be relative rather than absolute, potentially reflecting a postponement in the onset of disabling conditions to more advanced ages. This shift has significant implications for late-life quality of life and long-term care needs.

Alongside the increase in severe disability, this study also documents a rise in dependency among older adults, a pattern not previously observed in Spain. However, similar developments have been reported in countries such as the United Kingdom [38], in Germany [39], and in Japan [40]. These nations have more institutionalized or mixed long-term care systems, where formal services play a stronger role alongside family care. In contrast, Spain represents a Mediterranean, family-based model of care, with a much greater reliance on informal support provided mainly by relatives, particularly women [41]. This combination raises critical concerns about the sustainability of informal support systems in the face of demographic aging, smaller household sizes, and shifting family dynamics.

These findings offer a valuable complement to international indicators such as Healthy Life Years (HLY), which, despite their utility, often rely on simplified measures of limitation and do not distinguish severity or dependency. By using nationally detailed data, this study provides a more nuanced picture of disability dynamics and associated care needs, which are particularly relevant in familialist welfare contexts like Spain.

These changes call for a deeper examination of Spain’s long-standing care model. Traditionally, care for people with disabilities and dependent older adults has been provided within families, predominantly by women [17]. Yet major cultural and structural changes—including greater female labor market participation, aging of caregivers, and evolving family configurations—are challenging this model [42]. Martínez-Pastor [43], distinguishes between familial strategies, where care remains within the household (e.g., through reduced work hours or intergenerational support), and defamilialization, where responsibility shifts toward public services or private care providers. Although these categories were first developed in the context of child care, they are increasingly applicable to elder care.

Recent studies show that most dependent individuals in Spain are still cared for by relatives—especially spouses or children—with a significant gender bias [18]. However, preferences are shifting: nearly 17% of those over 85 now rely on external caregivers, and institutionalization affects about 8% of the disabled population [44, 45]. These trends suggest that defamilialization is gradually expanding, particularly among the oldest age groups, as new forms of care become more socially acceptable and financially viable.

Looking ahead, Spanish society will likely face a widening imbalance between the growing number of individuals requiring care and the shrinking pool of potential informal caregivers. This demographic tension may further accelerate the demand for alternative forms of care provision—whether market-based, community-driven, or publicly supported. Monitoring and anticipating these transitions will be essential for informing long-term care policies that are equitable, resilient, and adapted to demographic realities.

These findings should also be interpreted in the light of international policy frameworks on ageing. The World Health Organization (WHO) defines healthy ageing as the process of developing and maintaining the functional ability that enables wellbeing in older age [5]. According to this perspective, increasing years lived with severe disability and dependence highlight the need to create environments and services that support functional ability throughout the life course. In line with the WHO Decade of Healthy Ageing 2021–2030 [46], our results stress the importance of prevention, rehabilitation, and integrated long-term care policies that allow older adults not only to live longer, but to preserve autonomy and quality of life.