Why Cancer Is More Common With Age

Age is the single biggest risk factor for cancer. Cancer risk climbs sharply as people get older. This is true for cancer overall, and for most individual cancer types. This does not mean cancer is inevitable with age. It means the odds shift, and knowing that can help you take screening seriously as you get older.

The numbers make the pattern clear. Among people under age 20, cancer strikes fewer than 26 people out of every 100,000 each year. Among people 60 and older, that number climbs past 1,000 per 100,000. The median age at cancer diagnosis overall is 67. For specific cancers, the typical age at diagnosis varies: 63 for breast cancer, 66 for colorectal cancer, 68 for prostate cancer, and 71 for lung cancer.

Cells in your body divide constantly throughout your life, copying their DNA each time. Every division carries a small chance of a copying error, called a mutation. Most mutations are harmless or get repaired. But over decades, mutations can build up in the same cell. Cancer usually needs several specific mutations to develop, not just one. The longer you live, the more time your cells have had to build up these mutations. Over decades, enough of them can add up in one cell to turn it cancerous.

Age affects the body in other ways that matter too. Your immune system normally finds and destroys abnormal cells before they can grow into cancer. That system works less efficiently as people get older. Years of exposure to things that damage cells also add up over a lifetime. This includes sun exposure, smoking, and certain infections. All of this stacks the odds higher with each passing decade.

Getting older is not something you can avoid, and this is not a reason for alarm. It is a reason to take age-appropriate cancer screening seriously. Many screening guidelines are built directly around this pattern. Mammograms, colonoscopies, and other tests usually start at a specific age. That age is chosen because it is when risk starts climbing meaningfully for that particular cancer.

Breast, colorectal, prostate, and lung cancer all show the same climbing pattern with age, even though they affect different organs and have different risk factors. This consistency is part of why doctors treat age as such a central piece of information. It is not specific to one body part or one cause. It reflects something general about how cells change over a long lifetime.

None of this means younger people are safe from cancer. Some cancers, including certain leukemias, testicular cancer, and cervical cancer, are relatively more common at younger ages. And rates of some cancers, including colorectal cancer, have been rising among younger adults in recent years. Age is a strong pattern, not a rule that applies to every person or every cancer. Do not dismiss a persistent symptom just because you feel too young for cancer to be likely.

You cannot change your age. But you can control how you respond to it. Keep up with age-appropriate screening, even when you feel completely healthy, since many cancers cause no symptoms in their earliest, most treatable stage. Tell your doctor about your family's cancer history, since that can shift your personal screening schedule earlier than the general guidelines suggest.

Ask what cancer screening tests are recommended for your age, and when to start. Ask whether your family history changes that timeline for you specifically. Ask what symptoms, at any age, should prompt a visit rather than a wait-and-see approach.

• National Cancer Institute — Age and Cancer Risk.