The number of older people diagnosed with four or more diseases will double within the next 20 years due to rising levels of obesity and a lack of physical activity.

Researchers at Newcastle University found there will be large growth in the number of people with multiple diseases, known as 'multi-morbidity'.

By 2035, life expectancy is predicted to increase by 3.6 years for men and 2.9 years for women, however, the researchers estimate that two-thirds of that time will be spent living with four or more diseases.

Published in the journal Age and Ageing, the study also predicted that a third of people will be diagnosed with dementia, depression or a cognitive impairment.

Lead author Carol Jagger, professor of epidemiology of ageing at Newcastle University’s Institute for Ageing, developed a Population Ageing and Care Simulation model that takes into consideration characteristics including socio-demographic factors, health behaviours, chronic diseases and geriatric conditions.

The largest increase in diagnoses in the older population will be cancer (up by 179 per cent) and diabetes (up by 118 per cent), while arthritis and cancer will see the greatest rise in prevalence.

In the over-85s, all diseases apart from dementia and depression will more than double between 2015 and 2035.

The number of people in the UK aged over 85 is expected to double from 1.3 million in the next two decades.

“Much of the increase in four or more diseases, which we term 'complex multi-morbidity', is a result of the growth in the population aged 85 years and over,” said Professor Jagger.

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

The research paper says: “Poor health behaviours such as obesity and physical inactivity are risk factors common to a number of diseases, but have received little attention as risk factors for multi-morbidity.”

The authors argue that healthcare delivery is generally built on the treatment of single diseases but that patients with complex multi-morbidity need a different approach.

They call for a focus on prevention of disease and a bespoke healthcare service provision for patients with multi-morbidity.