In the US, cancer deaths and death rates increased year after year since records have been kept, reaching peaks in the early 1990s. Indeed, while 12,769 Americans were reported to have died of cancer in 1900 or 3.7 % of total 343,217 deaths, 158,335 cancer deaths were recorded in 1940, 553,768 in 2001, and 597,689 in 2010, or 11.2 %, 23 %, and 24 % of total deaths (1,417,269, 2,416,425, and 2,468,435, respectively). Although older statistics lack accuracy, they reveal that, while cancer was the eighth cause of death (64/100,000) in 1900, it has risen to be second only to heart disease since 1940, reaching a rate of 186/1000,000 in 2010 [315]. This progressive rise in cancer deaths is linked to four major factors: increasing population (Fig. 6.1), increasing longevity, and a shift to an older population (Fig. 6.2), placing more individuals at risk of exposure to carcinogens for longer periods, and hence, an increased probability of developing cancer.

As reported by the US Bureau of the Census, the US population expanded by 104 % between 1950 and 2010 (from 151.3 to 308.7 million). Moreover, during the same period, the over-65 population subset more than trebled: from 12.4 to 40.2 million (e.g., from approximately 7.9–13 % of the total US population, respectively), as shown in Fig. 6.2. As a result of the aging population, the average life expectancy in the US rose from 62.9 years in 1950 to 78.7 years in 2010. In addition, 76 million American children born between 1945 and 1964, the so-called baby boomers, will reach the age of retirement in the late 2000s, further increasing the size of the aging population. Aging increases the risk of developing cancer, as approximately 75 % of cancers occur in individuals 55 years of age and older. Moreover, the risk rises exponentially with increasing age in both men and women. For example, the average age-specific cancer death rates during the 2000–2010 for both sexes were 11.7¹ for the 30–34 age group, but rose to 153.8¹ for ages 50–54, 870.2¹ for ages 70–74, and peaked at 1,759.2¹ for individuals age 85 and over (Fig. 6.3) [316].