LEARNING OBJECTIVES

After studying this chapter, you will be able to

• Identify key features of the adolescent period.

• Describe underlying factors that may influence adolescent risk taking behavior.

Adolescence is a period of rapid and transformative physical, psychological, sociocultural, and cognitive development. The physical changes of puberty—including growth and maturation of multiple organ systems such as the reproductive organs and brain—lay a biological foundation for the other developmental changes. The adolescent brain is rewired, with resulting maturation of cognitive abilities in early adolescence. When these new cognitive abilities are combined with life experiences, we often observe development of social judgment, including judgment about risk and safety. Adolescence is also marked by critical transformation in the relationship of a young person to the world, as the social circles of peers and the adult worlds of work, pleasure, and social responsibility become more central and the family circle becomes somewhat less prominent—at least temporarily. Adolescents must learn to deal with an expanding social universe and must develop the social skills to find friendship, romance, employment, and social standing within multiple social spheres. Finally, a critical task of adolescence is the establishment of a stable sense of identity and the development of autonomy or agency. This development of identity often occurs only after a period of exploration, of trial and error in social roles and social behaviors. Although most adolescents navigate the often turbulent course from childhood to adulthood to become healthy adults and productive citizens, many fail to do so. Too many fall prey to social and behavior morbidities and mortality, and many fail to achieve their full potential as workers, parents, and individuals. Many suffer substantial short-term impairment and disability, and for many this impairment extends into adulthood. Many of these failures of adolescent development are the result of preventable health risk behaviors.

Adolescence is marked by increasing involvement in health risk behaviors. Between the ages of twelve and twenty-five, we observe the initiation of myriad health risk behaviors, including alcohol and drug use, smoking, sexual behaviors, delinquency, and behaviors leading to intentional and unintentional injuries—all of which can adversely influence health in the short and long term. For example, alcohol and drug use are the proximate causes of unintentional injuries during adolescence; they also can lead to adult addiction and social and health impairment. Sexual behaviors often result in unplanned pregnancy and sexually transmitted diseases, including HIV infection. These adolescent risk behaviors may profoundly influence health in adulthood.

Paradoxically, the rise in health behavior-related morbidities is the result of public health success in controlling and eliminating infectious diseases. As the result of advances in medical and public health understanding and technologies such as clean water, sanitation, and vaccines, enormous progress was made throughout the nineteenth and twentieth centuries in controlling these traditional causes of morbidity and mortality. Today adolescents in the developed world are primarily at risk from diseases that originate from behavioral and social circumstances. For example, a teen in the United States is much more likely to die from handgun violence or a motor vehicle injury than polio or whooping cough.

How can we explain this explosion of risk taking within each new cohort of adolescents? Multiple explanations have been suggested, most of which are explored in this volume. From an evolutionary viewpoint, risk taking may have had important survival value, with inquisitive young humans exploring new lands and willing to develop new ways of surviving in hostile environments. As such, developmental psychology often discusses risk taking as normal adolescent exploration that is an important part of the learning process of a young person.

Social and cultural factors including family instability, poverty, and racism also seem to drive adolescent risk-taking behaviors. While these responses may seem maladaptive from a societal viewpoint, they can also be seen as adaptive responses to unsupportive circumstances. Risk taking may also exist simply as part of the adolescent’s new identification with peers and the desire to attain adult status. Recent attempts to understand adolescent resiliency and the positive health impact of school and community connectedness can be seen as reciprocal processes: adolescents with greater social capital or with greater identification with society’s benefits and values may be more likely to eschew risk behaviors. Finally, these processes of risk taking can be understood at the level of brain chemistry, at the level of individual autonomic responses, and even as social processes that support risk taking.

Today preserving health is a function of understanding and altering the risk behavior of entire populations. This realization is vital because it suggests that population-based strategies to improve public health must begin early, before risk behaviors become ingrained habits. The implication, then, is that adolescents should be the primary foci of health promotion efforts. To understand the rich potential to affect public health through intervention with adolescents, consider just a few examples.

The current epidemics of obesity and diabetes in the United States are an outgrowth of sedentary behaviors combined with the overconsumption of high-calorie or empty-calorie food products (such as soda, chips, burgers, and fries). Similarly, the epidemic of hypertension in the United States is being addressed by changing the dietary and exercise behaviors of adolescents before they develop essential hypertension. Clearly, the public health battle to prevent cancer involves the prevention of tobacco use above and beyond any other single risk factor. Given the strong addictive properties of nicotine, it becomes clear that prevention efforts aimed at nonsmokers or new smokers are highly likely to serve public health; thus, once again adolescents become the critical population.

DISCUSSION QUESTIONS

1. What biological and physiological changes occur during adolescence? How does the sociocultural environment interact with these changes to affect the development of individual identity and later risk-taking behavior?

2. Discuss reasons why preventive interventions should focus on adolescents as a means to preserve health and alter risk.

CHAPTER 2

TRENDS IN ADOLESCENT AND YOUNG ADULT MORBIDITY AND MORTALITY

FREDERICK P. RIVARA ■ M. JANE PARK ■ CHARLES E. IRWIN JR.

LEARNING OBJECTIVES

After studying this chapter, you will be able to

• Explain the trends in morbidity and mortality among adolescents and young adults over the last twenty-five years.

• Discuss how high-risk adolescent behavior can affect health outcomes in adulthood.

• Recognize that adolescents and young adults are not a homogeneous group; rather, they are part of larger subgroups with diverse risk profiles.

It is important to consider both early adolescents and young adults along with the middle adolescent ages of fourteen through eighteen when discussing the health of this population.

Adolescence is an age of transition between childhood and adulthood. During this critical time, health habits and behaviors are established that affect health not only during adolescence but throughout the lifespan. Viewed in this context, the health and health care of adolescents take on even greater importance and much greater urgency.

In this chapter, we have chosen to define adolescence and young adulthood as encompassing the ages of ten through twenty-four years. This range includes early adolescents, ages ten through thirteen, who are making the transition from childhood into adolescence, as well as individuals ages nineteen through twenty-four, who are making the transition into adulthood. Given the economic, social, educational, and cultural changes in the United States over the last few decades, it is important to consider both early adolescents and young adults along with the middle adolescent ages of fourteen through eighteen when discussing the health of this population.

POPULATION CHARACTERISTICS

The 63 million adolescents and young adults ages ten through twenty-four in the United States accounted for about 21 percent of the population in the country in 2006 (Centers for Disease Control and Prevention [CDC], 2007a). Approximately 60 percent of this population is non-Hispanic white, 15 percent non-Hispanic African American, 4 percent Asian or Pacific Islander, and 1 percent American Indian or Alaskan Native. Eleven million adolescents and young adults, or 17 percent, reported their ethnicity as Hispanic or Latino.

Since 1990, the Hispanic population of adolescents and young adults has increased by 92 percent, while the African American population in this age group has increased by 25 percent and the non-Hispanic white population has increased by only 2.7 percent (see Figure 2.1). Hispanics are thus the largest minority group of adolescents and young adults in the United States.

The United States continues to be a country of immigrants. In 1990, 19 percent of adolescents less than twenty years of age lived in immigrant families. This increased to 22 percent by 2004 (U.S. Census Bureau, 2004). In 2006, there were 10.2 million adolescents and young adults (16.4 percent) who were living in poverty, accounting for 27.7 percent of all people in poverty in the United States (U.S. Census Bureau, 2007). There were an additional 12.5 million who were living at incomes between 100 and 200 percent of the poverty level. Over 12.5 million adolescents and young adults—or one in five—were uninsured in 2007, accounting for 26.6 percent of the 47 million uninsured people in this country.

FIGURE 2.1. Race and ethnicity of U.S. population ages ten to twenty-four years, 1990-2006

Source: CDC (2007a).

MORTALITY

Overall mortality among individuals 10 through 24 years has decreased over the last twenty-five years (1980 to 2004), as shown in Figure 2.2. Mortality has fallen from 30.8 per 100,000 to 18.7 among 10- to 14-year-olds, from 97.9 to 66.1 among 15- to 19-year-olds, and 132.7 to 94.0 among 20- to 24-year-olds (CDC, 2007b). However, during this twenty-five-year period, the decline has not been constant for all age groups. Death rates among 15- to 19-year-olds increased by 10 percent between 1985 and 1991, and by 4.7 percent among 20- to 24-year-olds between 1985 and 1988, and again by 6.2 percent between 1999 and 2003. This trend is remarkable because these are the only age groups in the United States for whom mortality rates actually increased during this period. To better understand these trends in mortality, it is necessary to disaggregate the data and examine etiologic groups.

Mortality from Natural Causes

Mortality from cancer has decreased steadily among all three adolescent age groups over the last twenty-five years (see Figure 2.3). Cancer deaths dropped by 40.5 percent among 10- to 14-year-olds, 33.3 percent among 15- to 19-year-olds, and 34.7 percent among 20- to 24-year-olds. Deaths from cardiac disease showed similar large declines, of 28.6 percent, 31.3 percent, and 18.9 percent in the three age groups, respectively. Respiratory disease- related death showed little progress among the 10- to 14-year-olds, but declined by approximately 25 percent in the two older age groups. Deaths from infectious causes were stable among the two younger cohorts, but actually increased by 60 percent (from 1.0 to 1.6) among 20- to 24-year-olds. This increase is due to deaths related to HIV infection, which accounted for 30,243 deaths among 20- to 24-year-olds from the beginning of the epidemic to 2002.

Death rates among 15- to 19-year-olds increased by 10 percent between 1985 and 1991, and by 4.7 percent among 20- to 24-year-olds between 1985 and 1988, and again by 6.2 percent between 1999 and 2003.

FIGURE 2.2. Mortality from all causes for ages ten to twenty-four years, U.S., 1981-2004

Source: CDC (2007b).

Mortality from Injuries

Injury—specifically unintentional injury, homicide, and suicide—accounts for almost three-quarters of all mortality in this age group. Overall injury mortality has declined substantially among people this age over the twenty-five-year period, although the aggregate data hide some important subgroup differences described below. Injury deaths decreased by 44.7 percent, 34.4 percent, and 32.3 percent among 10- to 14-, 15- to 19-, and 20- to 24-year-olds, respectively. Aggregate data also hide the considerable gender differences in mortality. Males have higher mortality rates than females, across these three age groups and for all three causes of injury mortality. For ages 10 through 24, the gap is highest for homicide, with males at a rate more than five times that of females. For unintentional injury mortality, males have just under five times the rate of females; for suicide, this ratio is 2.5.

Deaths related to HIV infection, which accounted for 30,243 deaths among 20- to 24-year-olds from the beginning of the epidemic to 2002.

Unintentional Injuries Mortality due to unintentional injuries declined steadily over the last twenty-five years in all three age groups: 53.0 percent among 10- to 14-year-olds, 44.4 percent among 15- to 19-year-olds, and 39.6 percent among 20- to 24-year-olds (see Figure 2.4). The largest single cause of adolescent and young adult mortality is motor vehicle crashes. There have been substantial and similar decreases in death rates from motor vehicle crashes across all three age groups: 40.9 percent decrease among 10- to 14-year-olds, 41.2 percent among 15- to 19-year-olds, and 40.7 percent among 20- to 24-year-olds. Motor vehicle crash rates peak for ages 20 through 24 and then decrease throughout the life span until age 70, when they peak again.

FIGURE 2.3. Mortality from selected causes for ages ten to twenty-fouryears, U.S., 1981-2004

Source: CDC (2007b).

FIGURE 2.4. Mortality from unintentional injuries for ages ten to twenty-four years, U.S., 1981-2004

Source: CDC (2007b).

Homicide Homicide rates demonstrated the largest fluctuation among all causes of deaths for adolescents over the last twenty-five years (see Figure 2.5). In all three age groups, homicide death rates were lower at the end of the period than at the beginning. All three age groups, however, had increases in the homicide rates during the late 1980s and early 1990s, peaking in 1993 and then declining to levels last seen in the 1960s through 1970s. Nearly all of this increase was due to homicides involving guns. Although the causes of this increase (and subsequent decrease) are complex, the sudden appearance of crack cocaine on the East and West Coasts and then spreading inland played a large role (Blumstein, Rivara, & Rosenfeld, 2000).

Suicide Trends in suicide deaths among adolescents and young adults are complex (Figure 2.6). Suicide increased among 10- to 14-year-olds from 0.8 deaths per 100,000 in 1980 to 1.34 in 2004. However, during that twenty-five-year period suicides increased in this group of young adolescents to a peak of 1.72 per 100,000 in 1995 before slowly dropping to their current levels. This represents a 115 percent increase from the rate in 1980. Suicide rates among 15- to 19-year-olds were lower in 2004 than in 1980. Again, however, this masks a 34 percent increase during the 1980s. Only among 20- to 24-year-olds was there a slow, steady decline in suicide deaths by an average of 1 percent per year over this twenty-five-year period.

FIGURE 2.5. Mortality from homicide for ages ten to twenty-four years, U.S., 1981-2004

Source: CDC (2007b).

FIGURE 2.6. Mortality from suicide for ages ten to twenty-four years, U.S., 1981-2004

Source: CDC (2007b).

Unfortunately, suicide rates among 10- to 24-year-olds have risen recently by 8 percent in 2003-2004 (CDC, 2007c). This overall increase was due to a rise in suicide among 10- to 19-year-old females and 15- to 19-year-old males. Although firearms remain the most common method of suicide for ages 10 through 24, hanging and suffocation have become more common among all suicides in this age group and now represent the most common method for completed suicides among females.

HIGH-RISK BEHAVIORS AS UNDERLYING CAUSES OF DEATH

By traditional markers such as rates of mortality, chronic disease, and hospitalization, adolescents and young adults are healthy. Most health problems in this age group stem from high-risk behaviors that jeopardize health. Moreover, these behaviors also have implications for health outcomes in the long term, including premature death. In 1993, McGinnis and Foege published a seminal paper on the actual causes of death in the United States. This was updated in 2004 by Mokdad et al., who described actual causes of death in 2000 (Mokdad, Marks, Stroup, & Gerberding, 2004). Half of all deaths are due to potentially modifiable factors: tobacco, poor diet and physical inactivity, alcohol consumption, microbial agents, toxic agents, motor vehicle crashes, guns, sexual behavior, and illicit drugs. Most important for both this chapter and the rest of this book is that all these modifiable behaviors also occur in adolescents and young adults, and for some behaviors (such as smoking) the majority begin during adolescence. Some behaviors and negative outcomes—including use of tobacco, alcohol, and illicit drugs and the rate of sexually transmitted infections—peak in the late teens and early twenties.

Half of all deaths are due to potentially modifiable factors: tobacco, poor diet and physical inactivity, alcohol consumption, microbial agents, toxic agents, motor vehicle crashes, guns, sexual behavior, and illicit drugs.

Tobacco Use

An estimated 440,000 people die from smoking-related causes each year in the United States (Mokdad et al., 2004). Nearly all smoking-related deaths occur after the age of 35, but the majority of adults who smoke began during adolescence. Eighty-two percent of adults who smoke started smoking before age 18, and virtually no adult smokers start after the age of 25. Young adults ages 18 to 25 have the highest prevalence of recent smoking—60 percent higher than that of adults over the age of 25 (Substance Abuse and Mental Health Services Administration, 2007).

The trends in any daily use of tobacco in the prior thirty days show a steady decline of use by twelfth graders between 1980 (20.3 percent) and 1992, when daily smoking reached a nadir of 17.2 percent in this age group (see Figure 2.7; Substance Abuse and Mental Health Services Administration, 2007). However, rates subsequently increased to a peak of 24.6 percent in 1997 and have since declined to a low of 12.2 percent in 2006. Among young adults ages 19 through 28, the prevalence of daily smoking in the prior nineteen days decreased between 1986 and 1994, stabilized for a decade, and then decreased again in the last two years to 18.6 percent in 2006. Recent studies suggest that nicotine addiction and symptoms of dependence can begin very soon after the onset of smoking, and they emphasize the dangers of early smoking exposure among youth (Kandel & Chen, 2000; DiFranza, Savageau, Fletcher, O’Loughlin, et al., 2007; DiFranza, Savageau, Fletcher, Pbert, et al., 2007; Rubinstein, Thompson, Benowitz, Shiffman, & Moscicki, 2007).

FIGURE 2.7. Daily cigarette use in last month

Source: Substance Abuse and Mental Health Services Administration (2007).

Prevention of smoking-related deaths is likely to be more successful if undertaken on a population basis to prevent regular smoking initiation than on an individual basis to promote cessation, especially among adolescents. The available evidence indicates that smoking cessation programs for adolescents have some effectiveness, but the effect size is small (about a 3 percent absolute difference in cessation; Sussman, Sun, & Dent, 2006). School-based smoking prevention programs have been popular, but there is little evidence that these programs have long-term effects on prevention of smoking (Wiehe, Garrison, Christakis, Ebel, & Rivara, 2005). In contrast, programs to increase the tax on cigarettes and implement smoking counteradvertising can potentially reduce adolescent smoking by as much as 26 percent (Rivara, Ebel, et al., 2004) and can result in large cost savings of between $590,000 and $1.4 million per life saved (Fishman et al., 2005).

Poor Diet and Physical Inactivity

Between the publication of the paper by McGinnis and Foege (1993) and its update by Mokdad and colleagues (2000), overweight and obesity became a dramatically worse problem (Ogden et al., 2006). The changes in weight among adolescents and young adults in the United States as documented in the National Health and Interview Surveys over the last forty years clearly demonstrate this change. In 1966-1970, the mean weight of 12-year-old males was 42.9 kg and 46.6 kg for females this age. In 1999- 2002, this had increased by 16.6 percent to 50.4 kg for males and by 11.6 percent to 52.0 kg for females (Ogden, Fryar, Carroll, & Flegal, 2004). Among 19-year-olds, mean weight increased by 7.7 percent among males and 14.1 percent among females between the 1971-1974 survey and the 1999-2002 survey. There were substantial changes in the weights of 20- to 29-year-olds as well; mean weight in males increased by 12.0 percent and among females by 18.4 percent between 1960-1962 and 1999-2002.

FIGURE 2.8. Body mass index, 1966-2002

Source: National Health and Nutrition Examination Survey.

The CDC has defined overweight as a body mass index (BMI) of 95 percent or higher for age and gender. The proportion of adolescents ages 12 through 19 who were overweight has nearly tripled, from 6.1 percent in 1971-1974 to 17.4 percent in 2002- 2004 (see Figure 2.8). This trend in overweight has not been uniform across ethnic and racial groups. In 2003-2004, non-Hispanic black girls ages 12 through 19 had the highest prevalence of overweight in this age group—25.4 percent. The prevalence of overweight also increased the most in this age group, nearly doubling between 1988-1994 and 2003-2004.

Overweight represents a mismatch between energy intake and energy expenditure, and is due to both poor diet and physical inactivity.

Overweight represents a mismatch between energy intake and energy expenditure, and is due to both poor diet and physical inactivity. The average number of calories consumed today is substantially higher than in the past. Moreover, the content of the diet has changed dramatically. One-third of children and adolescents consume fast food on a typical day (Bowman, Gortmaker, Ebbeling, Pereira, & Ludwig, 2004). Those who ate fast food consumed an average of 187 kcal more per day, including 9 grams more fat and 24 grams more carbohydrates. Overconsumption of fast food occurs in adolescence regardless of body weight, but overweight adolescents are less likely to compensate with increased energy intake at other times of the day, compared to nonoverweight adolescents (Ebbeling et al., 2004). Another significant source of “empty calories” among adolescents is soft drink consumption (Berkey, Rockett, Field, Gillman, & Colditz, 2004; AAP Committee on School Health, 2004). In one study, each additional sugar-sweetened drink consumed by children was associated with a 0.24 kg/m² increase in BMI (Ludwig, Peterson, & Gortmaker, 2001).

Unfortunately, a minority of adolescents engage in adequate physical activity. In 2005, only 36 percent of high school-aged adolescents had levels of physical activity that met recommended levels (CDC, 2006b). Males were more likely to meet the recommended levels than were females; non-Hispanic black girls ages 12 through 19 had the lowest proportion meeting recommended activity levels. Less than two-thirds of adolescents (64.1 percent) reported a more moderate level of activity, exercising for twenty minutes to promote cardiovascular fitness three or more times a week. This figure has changed little since it was first measured in 1993.

Although few adolescents will suffer the consequences of their obesity and lack of physical activity during their youth, nearly all overweight adolescents will be overweight as adults.