Researchers are offering a new way to understand why aging is so closely connected to chronic illness. In a review published in Aging-US titled “Aging as a multifactorial disorder with two stages,” scientists from University College London and Queen Mary University of London describe a model suggesting that diseases linked to aging may develop through two separate but connected phases over the course of life.
The review was written by David Gems and Alexander Carver from University College London, along with Yuan Zhao from Queen Mary University of London. Their work combines ideas from evolutionary biology with findings from modern biomedical research to explain how early damage in the body may later contribute to diseases such as cancer, arthritis, and infections.
How Early-Life Damage May Shape Health Decades Later
According to the researchers, the first stage begins earlier in life when the body experiences various forms of disruption. These can include infections, physical injuries, or genetic mutations. While the body is often able to repair or contain much of this damage, some of it may remain hidden rather than being fully removed.
The second stage occurs later in life as normal genetic activity starts changing in ways that are no longer beneficial to the body. These late-life biological changes can weaken the body’s ability to keep earlier damage under control. As a result, previously contained problems may gradually develop into disease.
The scientists argue that this process helps explain why many illnesses appear mainly in older adults even though their origins may trace back much earlier.
Why Diseases Like Shingles and Arthritis Appear With Age
The review highlights aging as a multifactorial process, meaning it is driven by many interacting biological factors instead of a single cause. The proposed model suggests that the combination of earlier damage and later-life genetic changes plays a major role in age-related disease.
For example, dormant viruses that remain inactive for years can become active again when the immune system weakens with age, leading to conditions such as shingles. In a similar way, injuries sustained in youth may eventually contribute to osteoarthritis as aging tissues become less resilient over time.
Inherited genetic mutations may also stay silent for decades before increasing the risk of diseases such as cancer or fibrosis later in life.
Evolutionary Biology and Aging Research
The researchers say their model builds on long-standing evolutionary theories of aging. One influential idea is that natural selection becomes weaker later in life, allowing harmful biological processes to emerge with age because they have less impact on reproduction and survival earlier in life.
The review also references studies involving the roundworm Caenorhabditis elegans. In these experiments, early mechanical damage in the worms eventually led to fatal infections in old age. The scientists suggest similar patterns may also occur in humans.
A New Framework for Healthier Aging
Overall, the review presents aging as a process shaped by multiple interacting causes that unfold over time. By separating aging into two major stages, early-life damage and later-life genetic activity, the researchers believe their framework could help guide future strategies aimed at disease prevention and healthier aging.
The findings also raise the possibility that reducing damage earlier in life or targeting harmful late-life biological changes could help lower the risk of chronic disease in older adults.