Final answer:
Illnesses and disease usually overtake accidents as the leading cause of death by the age of 70, with susceptibility to chronic diseases like cancer and hypertension increasing due to aging factors such as telomere shortening and DNA mutations caused by environmental mutagens.
Step-by-step explanation:
In adulthood, the leading causes of death shift from accidents to diseases and illnesses as people age. During early adulthood, accidents, including motor vehicle accidents, are a leading cause of death. However, as individuals transition into middle adulthood, chronic diseases become more prevalent. Diseases such as hypertension, heart disease, and cancer are diagnosed more frequently during middle adulthood, and their incidence increases with age. This change reflects the susceptibility to diseases related to aging and functional impairments.
Cell death contributes to aging in two primary ways. First, programmed factors such as the shortening of telomeres affect the aging process. The declining ability of cells to divide and repair themselves leads to decreased organ function and increased susceptibility to diseases. Second, damage-related factors, including exposure to environmental mutagens, can result in DNA mutations that accelerate the aging process and disease progression.
By old age, typically regarded as beginning in the mid-60s, the immune system has become less efficient, resulting in a greater risk of serious illnesses such as cancer and Alzheimer's disease. Illnesses and disease generally overtake accidents as the leading cause of death around the age of 70, although this can vary due to lifestyle, genetics, and environmental factors.