The number of adults aged 65 and over needing round-the-clock care will rise by over a third to more than one million during the next 20 years, experts have suggested.
The number of over-85s requiring 24-hour care will almost double to 446,000 in England by 2035, according to a new modelling study published in The Lancet Public Health.
The research, carried out by Newcastle University and the London School of Economics and Political Science, found there will be plenty of people living independent lives, with the number of over-65s living without care needs set to rise to 8.9 million - an increase of more than 60% from 5.5 million in 2015.
They predict this increase in independence will be seen mainly in men.
Nevertheless, they said the estimates predict a rise in the number of people living into old age with multiple long-term conditions, with the majority (80%) of older adults with dementia and in need of substantial care in 2035 likely to have two or more other diseases.
They said their study highlights the importance of ensuring that health and social care services adapt to the unprecedented needs of an increasing older population with complex care needs, with the authors warning that relying on the informal carers who provide around £57 billion worth of care in the UK is not a sustainable solution.
Professor Carol Jagger, from the Newcastle University Institute for Ageing, said: "The challenge is considerable.
"Our study suggests that older spouse carers are increasingly likely to be living with disabilities themselves, resulting in mutual care relationships that are not yet well recognised by existing care policy and practices.
"On top of that, extending the retirement age of the UK population is likely to further reduce the informal and unpaid carer pool, who have traditionally provided for older family members.
"These constraints will exacerbate pressures on already stretched social care budgets."
The team developed the Population Ageing and Care Simulation (PACSim) model as little research had previously been done on how levels of dependency might change for different generations of older people.
PACSim accounts for multiple risk factors for dependence and disability, including a wide range of sociodemographic factors (such as level of education) and health behaviours (for example, smoking status and physical activity), as well as 12 chronic diseases and geriatric conditions including coronary heart disease, stroke, hypertension, diabetes, arthritis, cancer and depression.
Using longitudinal data from three large nationally representative studies of adults (aged 35 and older), the study modelled future trends in social care needs for the population aged 65 and older in England between 2015 and 2035, according to varying levels of dependency.
Adults were categorised as high dependency if they required 24-hour care, medium dependency if they needed help at regular times daily, low dependency if they required care less than daily and were generally looked after in the community, or independent (without care needs).
Estimates suggest that the number of people over 65 will increase by just under 50% from 9.7 million in 2015 to 14.5 million in 2035, and highlight the very differing future care needs of men and women.
Between 2015 and 2035, life expectancy for men aged 65 is projected to rise by 3.5 years to 22.2 years, and the average number of years spent independent is expected to increase by 4.2 years (from 11.1 years to 15.2), while time spent living with substantial care needs (medium or high dependency) is likely to decline.
In contrast, for women average life expectancy at 65 will increase by just three years (from 21.1 to 24.1).
Over this time, the average number of years spent independent is expected to rise by less than a year (from 10.7 years to 11.6), and women will spend almost half of their remaining life with low dependency needs such as help with activities like washing and shopping, alongside a small increase in years requiring intensive 24-hour care (from two years in 2015 to 2.7 years in 2035).
Prof Jagger added: "Over the next 20 years, although young-old cohorts (aged 65-74) are more likely to enter old age independent, the proportion with multi-morbidities is projected to rise with each successive cohort, and this will result in a greater likelihood of higher dependency with further ageing.
"However, trends for men and women are likely to be very different, with women experiencing more low-level dependency than men, highlighting the importance of focusing on disabling long-term conditions such as arthritis that are more common in women than men."
The researchers also analysed how the burden of dementia with and without other chronic diseases will change demand for social care over the next 20 years.
For instance, while numbers of over-65s with dementia will fall by around a third (equivalent to 16,000 less people) by 2035, those with dementia and two or more conditions will more than double (equivalent to an additional 493,000 people).
Prof Jagger said: "This expanding group will have more complex care needs that are unlikely to be met adequately without improved co-ordination between different specialities and better understanding of the way in which dementia affects the management of other conditions."
Nick Forbes, senior vice chairman of the Local Government Association (LGA), said: "This report is a further warning of the crisis in adult social care and the urgent need to plug the immediate funding gap and find a long-term solution on how we pay for it and improve people's independence and wellbeing.
"With people living longer, increases in costs, decreases in funding, care providers closing and contracts being returned to councils, the system is at breaking point, ramping up pressures on unpaid carers who are the backbone of the care system.
"Adult social care services face a £3.5 billion funding gap by 2025, just to maintain existing standards of care. The likely consequences of this are more and more people being unable to get quality and reliable care and support, which enables them to live more fulfilling lives."
Alzheimer's Society chief executive, Jeremy Hughes, said: "These new estimates paint a challenging future, with the number of people needing constant care - the majority of whom will be living with dementia - starkly increasing in the next 20 years.
"After decades of starved funding, the social care system is buckling under the strain.
"Through our helpline we hear of people with dementia being forced to choose between a wash or a hot meal due to the limited time of a homecare visit, and ending up in hospital with an infection because they didn't have the support to shower each day."
A spokesman for the Department of Health and Social Care said: "In the Autumn we will set out our plans to reform adult social care alongside our long term plan for the NHS, so we can address the challenge of our growing ageing population head on and ensure services are sustainable for the future."
Copyright (c) Press Association Ltd. 2018, All Rights Reserved. Picture (c) Kirsty O'Connor / PA Wire.