14.3 Aging and Disease

As you read in Chapter 12, with each passing decade reaction time slows, the senses become less acute, organ reserves are depleted, and homeostasis takes longer. Skin, hair, and body shape show unmistakable senescence, while every internal organ—especially the heart and the brain—ages.

Primary and Secondary Aging

Gerontologists distinguish between primary aging, which involves universal changes that occur with the passage of time, and secondary aging, the consequences of particular inherited weaknesses, chosen health habits, and environmental conditions. One explains:

Primary aging does not directly cause illness, but it increases the impact of every secondary factor—cigarette smoking, viruses, obesity, and stress—and it makes almost every disease more likely. For example, with age, the heart pumps more slowly and the vascular network is less flexible, increasing the risk of stroke and heart attack. The lungs take in and expel less air with each breath so that blood oxygen is reduced and chronic obstructive pulmonary disease is more common. Digestion slows and the kidneys are less efficient, risking problems if people become dehydrated because they drink less to reduce incontinence, which itself is caused by an aging renal/urinary system.

Furthermore, healing takes longer if an illness or an accident occurs (Arking, 2006). For example, young adults who contract pneumonia usually recover in a few weeks, but in the very old the strain of pneumonia over several days can overwhelm a weakened body. Indeed, pneumonia is a leading cause of death for the oldest-old.

FIGURE 14.4 More Years to Live Even compared with a decade ago, fewer people die before age 65, which means that, for many causes, death is far more likely in old age. Most of the underlying conditions for these diseases were present in middle age.

Medical intervention affects the old differently than the young, reducing the effectiveness of drugs, surgery, and so on. For instance, anaesthesia may damage an older person’s brain or may cause the heart to stop. Temporary hallucinations and delirium after surgery are far more common for the old than for the young (Strauss, 2012).

A surprising example of the effects of age comes from medication that reduces hypertension. If systolic blood pressure is above 140, and diet and exercise do not lower it, drugs not only reduce it but also make strokes and heart attacks less likely for middle-aged adults. However, the same drugs for the same blood pressure are counterproductive for the oldest-old. For them, mild hypertension (140–160) may be protective because their slower homeostasis does not quickly respond to a sudden dip in blood pressure. That can be fatal (Beckett et al., 2008).

A developmental view of the relationship between primary and secondary aging harkens back to the lifelong toll of stress, as explained in Chapter 12. Allostatic load is measured by 10, or even 16, biomarkers—including cortisol, C-reactive protein, systolic and diastolic blood pressure, waste-hip ratio, and insulin resistance. All of these indicate stress on the body, and such stress, if ongoing, harms health.

Thus, measurement of allostatic load assesses the combined, long-term effect of many indicators, none necessarily dangerous alone. If many of these biomarkers are outside the normal range, people become sick and die, especially when aging already has reduced organ reserve (see Figure 14.4). In this way, lifelong responses to stress create a biological burden, a load that becomes lethal.

Compression of Morbidity

Ideally, prevention of the diseases of the old begins in childhood and continues throughout life, so societies need to recognize that public health and aging efforts are not only for the older adults of today but also for the future elder generations (Albert & Freedman, 2010). Illness can be delayed, and its severity can be limited by having established good childhood habits. Delayed illness is an example of compression of morbidity, which is reducing (compressing) sickness before death. There is good news here. In recent years, morbidity has been successfully compressed. For instance, unlike 30 years ago, most people diagnosed with cancer, diabetes, or a heart condition continue to be independent for decades (Hamerman, 2007).

Moving Along Her stiffening joints have made a walker necessary, but this elderly woman in Gujarat, India, is maintaining her mobility by going for a stroll every day.

AGE FOTOSTOCK/SUPERSTOCK

Compression of morbidity is a social and psychological blessing as well as a personal, biological one. A healthier person remains alert and active—in other words, experiences the optimal aging of the young-old, not the dependence of the oldest-old. Improved prevention, diagnosis, and treatment mean less pain, more mobility, better vision, stronger teeth, sharper hearing, clearer thinking, and enhanced vitality.

The importance of compression of morbidity is apparent with osteoporosis (fragile bones), which occurs because primary aging makes bones more porous, especially if a person is at genetic risk (North American women of European descent are more vulnerable, genetically, than women of other ethnic groups). A fall that would have merely bruised a young person may result in a broken wrist or hip in an elder. That leads to morbidity, sometimes for months, especially when hospitalization and bed rest cause infections and stress.

How can morbidity from osteoporosis be compressed? First, through better health habits earlier in life. Tobacco and alcohol weaken bones, as do low calcium and insufficient weight-bearing exercise. With strong bones, a fall does not cause a break. Second, through the use of special equipment, such as shoes, canes, and so on. These aids help elders strengthen their muscles and improve their balance, so morbidity does not even begin. Third, by becoming less fearful and fatalistic. By old age, the most common liability from a fall is fear. A prospective longitudinal study of Dutch elders (Stel et al., 2004) found that one-third of those who fell became overcautious, reducing their activity. That inactivity made all their organs less efficient. Ironically, only 6 percent of the falls for these elders resulted in serious injury, but the 94 percent with less serious injuries often moved less. That increased their morbidity.

This applies to every kind of primary aging. If the elderly selectively remedy whatever challenges their primary aging presents, morbidity will be compressed.