The number of older people with four or more chronic diseases is expected to nearly double by 2035, researchers at the Newcastle University Institute for Ageing have reported.

As life expectancies are climbing across the board, the global healthcare system is forced to deal with an influx of elderly patients, many of whom suffer from a medley of chronic illnesses, Carol Jagger, PhD, and colleagues in the United Kingdom wrote. The number of people aged 85 and up is expected to double over the next two decades, and for that population, multi-morbidity is the norm.

“Healthcare delivery was built, and generally remains centered, on the treatment of single diseases,” Jagger and co-authors wrote. “Over the last decade, the growing number of older people has become a considerable challenge to health and social care service provision and funding, as over 50 percent have at least two chronic conditions.”

These diseases, which range from arthritis and cancer to dementia and depression, are not only lowering quality of life for these patients, but upping national healthcare costs, increasing dependency and normalizing polypharmacy, the authors said. They also included coronary heart disease, diabetes, hypertension, respiratory illnesses and stroke in their analysis.

Cancer and diabetes are expected to see the greatest jump in diagnoses between 2015 and 2035, Jagger et al. found, increasing by 179.4 percent and 118.1 percent, respectively. Arthritis and cancer are projected to see the greatest rise in prevalence.

In those 85 years old and up, all diseases barring depression and dementia are expected to more than double in absolute numbers over the next 20 years.

“More worryingly, our model shows that future young-old adults, aged 65 to 74 years, are more likely to have two or three diseases than in the past,” Jagger said in a release from Newcastle University. “This is due to their higher prevalence of obesity and physical inactivity which are risk factors for multiple diseases.”

The researchers also said that at least a third of all new multi-morbidity cases will include a mental illness—either depression, dementia or another cognitive impairment.

Jagger and colleagues emphasized the need for a new healthcare approach that can accommodate patients with multiple comorbidities.

“These findings have enormous implications for how we should consider the structure and resources for the NHS (National Health Service) in the future,” Jagger said. “Multi-morbidity increases the likelihood of hospital admission and a longer stay, along with a higher rate of readmission, and these factors will continue to contribute to crises in the NHS.”

Jagger et al.’s work was published this week in Age and Ageing, the scientific journal of the British Geriatrics Society.