Abstract
BACKGROUND: Existing models for forecasting future care needs are limited in the risk factors included and in the assumptions made about incoming cohorts. We estimated the numbers of people aged 65 years or older in England and the years lived in older age requiring care at different intensities between 2015 and 2035 from the Population Ageing and Care Simulation (PACSim) model. METHODS: PACSim, a dynamic microsimulation model, combined three studies (Understanding Society, the English Longitudinal Study of Ageing, and the Cognitive Function and Ageing Study II) to simulate individuals' sociodemographic factors, health behaviours, 12 chronic diseases and geriatric conditions, and dependency (categorised as high [24-h care], medium [daily care], or low [less than daily] dependency; or independent). Transition probabilities for each characteristic were estimated by modelling state changes from baseline to 2-year follow-up. Years in dependency states were calculated by Sullivan's method. FINDINGS: Between 2015 and 2035 in England, both the prevalence of and numbers of people with dependency will fall for young-old adults (65-74 years). For very old adults (≥85 years), numbers with low dependency will increase by 148·0% (range from ten simulations 140·0-152·0) and with high dependency will almost double (increase of 91·8%, range 87·3-94·1) although prevalence will change little. Older adults with medium or high dependency and dementia will be more likely to have at least two other concurrent conditions (increasing from 58·8% in 2015 to 81·2% in 2035). Men aged 65 years will see a compression of dependency with 4·2 years (range 3·9-4·2) of independence gained compared with life expectancy gains of 3·5 years (3·1-4·1). Women aged 65 years will experience an expansion of mainly low dependency, with 3·0 years (3·0-3·6) gained in life expectancy compared with 1·4 years (1·2-1·4) with low dependency and 0·7 years (0·6-0·8) with high dependency. INTERPRETATION: In the next 20 years, the English population aged 65 years or over will see increases in the number of individuals who are independent but also in those with complex care needs. This increase is due to more individuals reaching 85 years or older who have higher levels of dependency, dementia, and comorbidity. Health and social care services must adapt to the complex care needs of an increasing older population. FUNDING: UK Economic and Social Research Council and the National Institute for Health Research.