▎ WuXi AppTec content team editor
The aging of the global population is accelerating, and ageing is often accompanied by the decline of physical functions and the development of a variety of diseases. Understanding how the elderly population gradually transitions from a healthy state to suffering from chronic disease or death, and what are the characteristics and speed of the onset of the disease, is of great reference significance for the formulation of interventions and the planning of the health care system.
Recently, The Lancet Healthy Longevity published a large-scale study that quantified the trajectory of disease in the elderly population. The study reported four key findings:
Among healthy older people, the most commonly occurring disease is cancer, which affects 10.1% of people;
4.8% of people lose independence, develop disability or dementia, and are at higher risk of developing disability or dementia after stroke;
It is worth noting that among the healthy people aged ≥ 70, 80.6% of them are still able to stay healthy for the next 5 years.
And increased age is closely associated with an increased risk of almost all health problems. In addition, women of the same age are healthier than men.
The concurrent review article notes that the study "greatly enriches our understanding of the shift in health in older adults."
Screenshot source: The Lancet Healthy Longevity
Rich, ubiquitous data
The study is based on a secondary analysis conducted by the well-known ASPREE study. ASPREE is a randomized, double-blind, placebo-controlled clinical trial exploring the effects of low-dose aspirin on healthy, independent lifespan in healthy older people. The analysis focused on the transition of these older adults from their health status to their first illness event( including heart events such as cancer, stroke, hospitalization for myocardial infarction and heart failure, as well as physical disability or dementia) and eventual death. These disease events, which the study chose to focus on, are the main reasons for the loss of healthy life expectancy in people over the age of 70.
The ASPREE study, which began in 2010 and was conducted in 50 clinical centres in Australia and the United States, included 19,114 older adults ≥ 70 years of age who were initially healthy and had no history of cardiovascular events, dementia or major physical disabilities, and had a high 5-year survival rate. Common aging disorders were also systematically assessed at follow-up follow-up, and cognitive function and physical disability status were regularly assessed. Therefore, this provides a unique and detailed data resource for understanding the aging trajectory that is broadly applicable to healthy older populations.
Image credit: 123RF
The most common deaths occur after cancer, and stroke is an important cause of disability or dementia
The median follow-up was up to 4.7 years, during which time:
1933 people (10.1%) developed cancer,
487 people (2.5%) had a cardiac event,
398 (2.1%) had a stroke,
924 (4.8%) develop persistent physical disability or dementia,
1052 (5.5%) died.
1539 people (80.6%) did not have any of the above incidents.
▲ All 12 hypothetical disease/death trajectories. Arrows along the line data indicate the number of people and the incidence per 1000 person-years. "Enter" indicates the number of people entering each state, and "leaving" indicates the number of people who are no longer in that state at the end of the follow-up. (Image source: References[1]; Translation: New Perspectives on Medicine)
Similarly, if chronic disease occurs for the first time after focusing on health status, it is cancer (9.7%), followed by disability or dementia (4.3%), cardiac events (2.2%) and stroke (1.7%). 1.5% of people died without the above diseases.
In all 12 hypothetical disease/death trajectories, mortality after disease occurred was much higher than the probability of progression from healthy state to death.
The probability of progression to death after the onset of cancer is 158 cases per 1000 person-years, and the probability of progression to death after stroke, cardiac event and disability or dementia is 112 cases/1000 person-years, 88 cases/1000 person-years, and 69 cases/1000 person-years, respectively.
In a healthy state, the probability of progression to death is only 4 cases/1000 person-years.
Of all deaths, 47.6% (501/1052) were also diagnosed with cancer for the first time, and 12.3% (129/1052) had a physical disability or dementia for the first time.
The highest incidence of disability or dementia for different diseases was stroke (55 cases/1000 person-years), followed by cardiac events (32 cases/1000 person-years), cancer (16 cases/1000 person-years) and health status (11 cases/1000 person-years).
Increased age is an important factor in the disease, and men are at higher risk
The research team also analyzed the effects of age and gender.
For most health problems (except for progression to disability or dementia from stroke), age (≥75 versus <75 years) was significantly associated with accelerated progression.
For example, ≥ 75-year-olds have twice the mortality rate after cancer than < 75-year-olds (223 cases/1000 people-year vs 110 cases/1000 people-years).
For every 5 years of age, the risk of transitioning from healthy status to death nearly doubles (HR 1.99), the risk of developing disability or dementia from cardiac events (HR 1.97), and the risk of death after stroke (HR 1.988).
Of the 12 aging trajectories, men were significantly associated with 5 accelerated progressions.
From health to the development of cancer, cardiac events or death, women are at 41%, 50 percent and 39 percent lower risk than men, respectively.
After developing cancer, men are twice as likely to develop disability or dementia as women (21 cases/1000 people-years vs 10 cases/1000 people-years).
After disability or dementia, the mortality rate for men is also twice that of women (94 cases/1000 person-year vs 49 cases/1000 person-year).
Compared to men of the same age, women aged 75 and 85 are more likely to remain healthy.
For healthy older people aged 75, the total expected remaining life expectancy for men and women is 4.87 and 4.93 years, respectively, and the expected remaining healthy life expectancy for women is longer (4.60 vs 4.40 years).
For healthy elderly people aged 75, the 5-year mortality rate for men was 7.03%, higher than the 4.13% for women. The 5-year mortality rates for healthy men and women aged 85 were 21.91% and 13.51%, respectively.
The 5-year probability of disability or dementia in healthy men and women aged 75 was 4.75% and 4.52%, respectively, compared with 11.90% and 12.70% at age 85.
▲Probability of health status over time. (A) 75 male, (B) 75 female, (C) 85 male, (D) 85 female. (Image source: References[1])
Understand aging and promote healthy aging
The paper notes that these findings provide unique insights into the frequency and trajectory of disease events, as well as the impact of age and gender.
Most healthy older people are able to remain healthy, which underscores the benefits of effective preventive interventions. Individual-level prevention through guidance by healthcare professionals, and at the population level through measures such as screening, can help reduce the impact of risk factors that are often the common target of interventions for multiple diseases. Cancer screening is of particular concern.
These results are also important for care planning for the elderly population. The United Nations has initiated the Ten-Year Action Plan on Healthy Ageing to better understand aging and prevent the elderly from transitioning from a healthy state to chronic disease, loss of independence and death, which will promote the improvement of the lives of the elderly.