Why Does Cancer Become More Common with Age? Exploring the Biological Links and Understanding Common Cancer Types in Older Adults.
Written by Caitlin Ng
Cancer is a disease caused by uncontrolled division of abnormal cells in a part of the body. The vast majority of cancer cases occur in individuals over 50, and a remarkable one-third of all diagnoses in the UK occur in people 75 years of age or older providing strong evidence that aging significantly raises the risk of developing cancer (Cancer Research UK 2023). These figures demonstrate the significant health challenges that happen with age, but why does this happen?
There are many factors that show a connection between aging and cancer including: DNA mutations, immune system decline, cellular senescence leading to inflammation, and hormonal imbalance.
In our daily lives, we are exposed to carcinogens, substances that can cause cancer such as UV radiation, and natural errors during cell replication, that can accumulate over decades and mutate our DNA. As we age, these damages overwhelm the body's ability to repair DNA, resulting in mutations that disrupt normal cell growth, increasing the likelihood of cancer development. These mutations frequently affect oncogenes, which maintain the speed of the cell cycle, and tumour suppressor genes, which prevent the cell cycle from going too fast; mutations in these genes cause the cell cycle to speed up and go out of control, potentially leading to malignant transformation and cancerous growth (National Human Genome Research Institute 2024).
The immune system protects the body against illness and infection, as people age their immune system naturally weakens through a process known as immunosenescence. T cells are a type of white blood cells that scan the body for infected or cancerous cells, then locate the cancer cells and destroy them. However, due to the deterioration of the thymus gland due to age fewer T cells are produced and therefore weakens the immune system (Medicine Net n.d.). Another type of white blood cell, natural-killer cells (NK cells) detect abnormal cells and inject toxic proteins into the cell such as Perforins to destroy the cell. Furthermore, NK cells release signal molecules called cytokines which can help engage additional immune cells at the site of tumor growth, however, due to aging NK cell activity diminishing, their ability of identifying and destroying cancerous cells leading to tumour growth is reduced(National Library of Medicine 2023).
Senescent cells are body cells that eventually stop multiplying but remain metabolically active, more of these cells enter this stage as we age. Even though these cells prevent damaged cells from proliferating they release inflammatory signals called the senescence-associated secretory phenotype (SASP). SASP can signal the immune system to attack and remove damaged cells however can promote tissue repair but can also support cancer cell growth (Nature reviews clinical oncology 2022).
Hormones are chemical messengers that regulate many processes in the body. However, hormonal imbalance can increase the incidence of developing cancer. Prolonged exposure to oestrogen, which promotes breast and uterine cell growth, increases the risk of breast or endometrial cancer mutations. Testosterone can fuel the growth of prostate cells which also increases the risk of prostate cancer due to testosterone levels declining with age and prostate cells responding abnormally. Additionally, imbalances in insulin and IGFs can also stimulate tumour growth, particularly lung, breast, prostate, colorectal, pancreatic, and skin cancer. Therefore, hormone regulation is crucial in controlling the development of cancer in people of age.
In conclusion, DNA mutations, immune system decline, cellular senescence, and hormonal imbalance all outstandingly contribute to the increased cancer risk in older adults by not only weakening the immune system but also increasing the incidence of abnormal or malignant cells to develop and proliferate in the body, leading to the development of cancers such as lung, breast, prostate, colorectal, and skin cancer in aging populations. However, through increased awareness, routine cancer screenings, and the adoption of healthier lifestyle choices, it is possible to mitigate these risks. While aging remains one of the strongest risk factors for cancer, proactive measures and early detection can significantly alter the direction of the disease, offering better quality of life and survival rates for older adults.
Edited by Olivia Zhang