Cancer can develop for many reasons. As people age, their bodies change in ways that make cancer more likely. These include being exposed to cancer-causing substances for a longer time, more damage to DNA, a weaker ability to repair DNA, and changes in the immune system that make it harder to find and destroy abnormal cells.
Making healthy lifestyle choices can help lower cancer risk. Quitting smoking, drinking less alcohol, keeping a healthy weight, and limiting sun exposure can all help. Some causes of cancer are still not fully understood.
Lung Cancer Risks
Cigarette smoking causes 80 to 90 percent of lung cancers. When a person stops smoking, their risk of getting cancer starts to go down right away. Over time, their risk becomes nearly the same as someone who never smoked.
Lung cancer in people who never smoked or who smoked very little is becoming more common. These cases may be linked to genes, things in the environment, or other causes that are not yet fully understood.
Other Types of Cancer Risk
Many things can increase the risk of cancer. These may be related to chemicals, the environment, or lifestyle choices, such as:
- Chemicals, like pesticides that kill bugs and weeds
- Too much alcohol
- Too much sunlight (raises skin cancer risk)
- Obesity
- Exposure to radiation
- Certain viruses (HPV raises the risk of cervical cancer; hepatitis raises the risk of liver cancer)
Last Reviewed and Updated: October 2026
By: AGS/HiAF Public Education Committee, HealthinAging.org Content Reviewers