Most people certainly agree that the “growing up” part of life is more agreeable and productive than the “growing old” part. As this book emphasizes, growing old both happens by itself, inexorably, and is often compounded by harmful lifestyles, and always concludes with its inevitable unwanted ending. How Aging Works: What Science Can Do About It, offers new scientific understanding about what occurs as people grow old, and provides simple, easy to carry out recommendations on how to live longer, enjoyable lives.

Chapter 1: The Biology of Aging and How to Slow it Down. This chapter includes basic information about what actually takes place in human bodies as adults begin to notice and then submit to the realities of growing old. Aging results from first, the barely perceptible but then, gradually worsening failure of formerly highly efficient genetically controlled processes to continuously repair and replace DNA (deoxyribonucleic acid) and other vital regulatory molecules; widespread dangers arise from bombardment by X-irradiation, cosmic rays, radon, reactive oxygen species, air pollution, and other toxic products. Aging is not a disease, but an inescapable stage in ordinary life; the crucial connection between aging and disease stems from both the body’s cumulative molecular damage and lowering of protective defense mechanisms—which pave the way for the development of heart disease, cancer, COPD (chronic obstructive pulmonary disease), stroke, Alzheimer’s dementia, diabetes, falls and fractures—all the classic hazards of growing old.

Chapter 2: Life Expectancy and Aging in America. The second chapter provides a quick look at how people lived and died at the turn of the 20th century and illustrates a few of the astonishing, subsequent advances that revolutionized medical care and public health. In 1900, slightly over 10 percent of babies died at birth and another nearly 10 percent died in their first decade of life; today, fewer than 1 percent of newborns fail to celebrate their 10th birthdays. Life expectancy dramatically lengthened, from 47.3 years in 1900 to 78.7 years in 2002. Note also the quadrupling of the number of Americans. In 1900 the population was a little over 76 million; in 2000, thanks to a gigantic influx of immigrants the population swelled to 281 million, and at last count (2014) to 314 million.

Chapter 3: Brain Cells and Memory. Scientists have known for decades that brains get smaller as they age, but until recently, experts believed that the shrinkage was caused both by death of neurons and age-related loss of cognitive performance. Brains still get smaller, but the number of nerve cells remains virtually constant owing to loss of some neuronal fibers and compaction. The truly stunning news of the last few years, which completely overturned previous neuroscientific axioms, is the discovery that human brains are not doomed to steady attrition from ongoing death of neurons and kindred cells—whether from natural causes, disease, or injury—but that new brain cells can be formed and old ones replaced, owing to the presence of stem cells: incredibly versatile progenitor cells that can differentiate into nerves or their neighboring supporting cells. Newborn neurons, once given a start, mature into normal neuronal structures, integrate with other nerves, and develop synapses. Brains try, to the extent possible, to deal with age-induced functional deprivation by reprogramming how they process information and execute orders. Exercise and/or physical activity has long been known to keep brains healthy. In addition, newly discovered growth factors may enhance the brain’s wellbeing, and cognitive functions.

Chapter 4: Strength and Speed. Starting as early as around 20 years of age and continuing throughout the remaining lifetime, adult human bodies lose 40 percent or more of their body’s muscle mass, slowly at first, then accelerating. Sarcopenia explains why world-class athletes retire from competitive sports but the process invariably happens to ordinary men and women as well. Sarcopenia causes loss of strength, speed, and coordination, but is also, commonly, worsened by further shrinkage and enfeeblement of muscles known as atrophy. Together, sarcopenia plus atrophy—through failure of middle-aged and elderly adults to engage in physical activity and/or exercise—are a major source of weakness, poor balance, and inefficient coordination leading to falls and fractures, with serious and sometimes fatal consequences. Physical activity-exercise is essential to maintaining good health in aging persons, including adults with most medical conditions and disabilities.

Chapter 5: Sexuality includes people’s sexual habits and sexual activities, which begin to fade in adult life and, not surprisingly, at widely different rates and times of onset. The prevailing myth that old folks have—or should have—given up sex long ago has finally been refuted by a nationwide scientific survey in 2007 of the frequency of sexual activities among 3004 U.S. adults aged 57 to 85. The results confirm that many older adults remain sexually active, though the frequency of activity decreases with age and women have lower rates of activity than men at all ages. After menopause, the wall of the female vagina becomes thinner and a little stiffer, and the lining membrane gradually gets drier owing to loss of natural lubrication, which can usually be alleviated by an over-the-counter vaginal lubricant. The chief problem in men is erectile dysfunction, which is tightly linked with age: in fewer than 2 percent of men younger than 40; 26 percent aged 50 to 59; and 61 percent 70 and older. Erectile enhancers, like Viagra, the fastest selling drug of all time, have created a second sexual revolution, this one for elderly men and their partners. (The FDA has recently approved flibanserin, a novel medication to boost women’s sex drive.).

Chapter 6: Aging and Heart Disease. As life expectancy steadily increased during the 20th century and while tuberculosis, pneumonia, and other infections were decreasing, heart disease, chiefly coronary artery disease (CAD), from atherosclerosis, or hardening of the arteries, became the principal cause of death among Americans. Genetic history plays an important role in the development of CAD, but increasing age and lifestyle-dependent risk factors that start with abnormalities of the inner lining of blood vessels, endothelium, often progress to serious complications. Dangerous lipids, high blood pressure, cigarette smoking, diabetes mellitus, overweight or obesity, and lack of physical activity narrow arterial channels for blood flow and sometimes cause total obstruction leading to a heart attack, myocardial infarction, or other vascular complications. Treatment of atherosclerosis by rerouting and/or opening obstructed arteries has dramatically lowered death rates from CAD. Furthermore, prevention of CAD by reducing of the reversible risk factors has improved outcomes, but needs to be greatly intensified (Chapter 6).

Chapter 7: Aging and Cancer. Deaths from cancer and heart disease are both decreasing among Americans; but deaths from cancer are declining less rapidly than those from heart disease, which means that in the foreseeable future cancer will become the leading cause of U.S. mortality. Tobacco is by far the most important cause of death from cancer, but as the American Cancer Society has emphasized, poor nutrition, physical inactivity, and excess weight are also important causes of preventable death. Less than 1 percent of all new cancer diagnoses involve children 14 and younger. By contrast, the incidence of new cancers begins to rise in middle age and typically escalates in the elderly. In addition, 5-10 percent of all malignancies are caused by the inheritance of a cancer susceptibility gene, usually of the breast or colon, which confers substantial risk. New gene-based treatments—using agents specifically aimed against cancerous genes or gene products—have significantly improved outcomes, provided that the incriminating molecular target can be definitively identified. More such therapeutic partnerships are on the way.

Chapter 8: Aging and COPD. The term COPD combines 2 pathologic entities, emphysema, anatomic destruction of the tiny air sacs of the lungs, and chronic bronchitis, inflammation of large and small airways; both disorders cause abnormal slowing down—from obstruction—during inhalation and, especially, exhalation of airflow during breathing. In 2008, COPD moved from fourth to third place, displacing stroke, among causes of death in Americans. Current surveys document impressive increases in prevalence of COPD in multiple countries from the steadily enlarging population of aging adults. Cigarette smoking was once viewed as the unique genesis of COPD, but dusty occupations and air pollution now also contribute. Treatment improves both shortness of breath and exacerbations of cough and sputum production, but no cure exists. Stopping smoking is essential, but existing anatomic abnormalities become permanent. As tobacco smoke and environmental pulmonary toxins persist, the COPD epdemic will flourish.

Chapter 9: Aging, Stroke, and High Blood Pressure. Stroke, known also as cerebrovascular accident, is an acute loss of brain function from shortage of blood flow, and stoppage is disastrous. Two kinds of stroke are recognized, ischemic and hemorrhagic, each with 2 subcategories. Ischemic strokes, by far the most common, are caused by a thrombus within an atherosclerotic artery, and the remainder from an embolus, a blood clot that breaks off, flows through the arterial circulation, and often ends up plugging a vessel in the brain. Two kinds of less common hemorrhagic strokes are recognized: intracerebral hemorrhage, bleeding directly into the brain, and subarachnoid hemorrhage, bleeding into the anatomic space completely surrounding the brain and spinal cord. Improved diagnosis of stroke requires rapid imaging for diagnosis, then dissolving the causative thrombus, and new methods now permit mechanical removal of obstructing lesions.

The definition of high blood pressure, or hypertension, was revised in 2014. The usual measure remains 140/90 mmHg, but for people 60 years or older, either a systolic pressure of ≥ 150 mmHg or a diastolic pressure ≥ 90 mmHg is now standard. High blood pressure is highly prevalent and age-dependent, and only a small percentage of its victims are diagnosed and properly treated with anti-hypertensive medications, usually 2 or more kinds. Common complications are myocardial infection, stroke, heart failure, kidney failure, and death. Stopping smoking, losing weight, and practicing a low-salt diet are essential elements of treating high blood pressure.

Chapter 10: Aging, Alzheimer’s Disease, and Other Dementias. Doctor Alois Alzheimer will forever be famous for his 1906 description of what are now called amyloid plaques, composed of a toxic protein named amyloid beta, and neurofibrillary tangles, containing another toxic protein known as tau. Early-onset Alzheimer’s patients develop dementia between the ages of 30 and 60; there is a distinct family predisposition, and roughly half the cases have an inherited genetic abnormality. Late-onset Alzheimer’s starts around 60-65 years and increases dramatically, from about 5 percent of men and women aged 65 to 74 to nearly 50 percent of those 85 and older, mainly women. New imaging and biochemical studies document the presence of mild cognitive impairment well before the classic manifestations of full-blown disease appear. Early diagnosis is now possible, but available drugs are largely ineffective and no cure is in sight. As life expectancy and the world’s population increase, the scourge of Alzheimer’s disease will pose a gigantic health problem.

Chapter 11: Aging and Diabetes. Around the end of World War II, the prevalence of diabetes (properly called diabetes mellitus), began to increase modestly, then intensified, especially among Americans 65 and older. Type 1 diabetes accounts for 5 to 10 percent of cases and is caused by destruction of pancreatic beta cells, the body’s sole source of insulin. Type 2 diabetes accounts for 90 to 95 percent of cases and occurs by the development, first, of insulin resistance then loss of beta cells. Diabetes is a menacing disease that damages small (micro) vessels involving eyes (blindness), kidneys (uremia), and nerves (wobbliness, low blood pressure). Most deaths (> 65 percent) arise from atherosclerosis-related heart disease and less commonly stroke; associated high blood pressure and dangerous lipids require treatment. Importantly, diabetes can be prevented by weight loss and exercise. Good control of blood sugar (glucose)—which should be monitored to ensure a concentration of hemoglobin A1c of 7.0 percent or less—forestalls development of complications and lengthens life.

Chapter 12: Aging, Osteoporosis, and Falls and Fractures. Osteoporosis accounts for the fact that “fully half of all postmenopausal women will incur an osteoporosis-related fracture in their lifetimes.” Men also suffer from it, but 10 years or more later. Age, gender, race, genetic and other factors all play a role. The diagnostic gold-standard remains measurement of bone density by dual-energy x-ray absorptiometry, or DXA. Moreover, 1 out of 3 non-osteoporotic American adults 65 and older falls each year, and once someone falls, the odds increase that she/he will fall again within 1 year. Over 400 risk factors are known, the most important being weakness; underlying diseases and medications also contribute. Bone health in the elderly starts with regular exercise and adequate calcium and vitamin D. Several medications are available to treat osteoporosis, but side effects are common and patient-physician consultation is recommended to assist making an optimum decision.

Chapter 13: Smoking and Aging. Tobacco is the leading cause of preventable death in the U.S. each year with nearly half a million deaths, mainly from lung cancer and cardiovascular disease. Tobacco-related deaths in high-income countries are projected to decrease slightly, whereas increasing millions will occur in medium- and low-income countries. Cigarette smoke contains hundreds of toxins, including 11 powerful (class A) carcinogens, but exactly how they cause morbidity and mortality is unclear. Another key ingredient is nicotine, a highly addicting chemical, the absence of which causes regular smokers to begin to notice withdrawal symptoms, and to quickly light up another cigarette for relief. Eighty percent of smokers who try to quit on their own have resumed smoking within a month. Improved success comes from use of 5 nicotine substitutes, and 2 more potent drugs, buproprion and varenicline; both increase rates of cessation but are complicated by side effects, especially varenicline.

Chapter 14: Obesity and Aging. Beginning during the 1980s, Americans began to gain lots of weight. By 1999 and continuing today, 33.4 to 35.0 percent of all adult women and men had become overweight; at the same time, 30.5 to 36.1 percent had become obese: two-thirds of all adults. The higher the weight the greater the risk for obesity’s serious complications, including coronary artery disease, high blood pressure, stroke, type 2 diabetes, and several types of cancer: all preventable. The standard indicator of an individual’s height and weight is the Body Mass Index, BMI = (weight [kg] ÷ height [m2]); or BMI = (weight [pounds] ÷ height [inches2] x 703 [conversion factor]). BMI values 18.5 to 24.9 are healthy, 25.0 to 29.9 indicate overweight, values 30.0 to 39.9 indicate obesity; and values 40.0 or higher indicate morbid obesity. Not all excess body fat is equally dangerous. Abdominal, or visceral, fat is the main site of hazardous adipose tissue, whereas subcutaneous fat is relatively inert. It is hard to lose weight and most people who succeed gain most of it back. Current indications for bariatric (weight-loss) surgery are widening owing to its effectiveness in losing and sustaining weight loss. Surgery both prevents diabetes and leads to its remission, and reduces long-term mortality from heart disease, diabetes, cancer, and the metabolic syndrome.

Chapter 15: Alcohol and Aging. The health-damaging effects of alcohol are widely known and advertised, but its health-benefitting properties remain uncertain and debatable. The U.S. Department of Agriculture states that “Moderate Alcohol Consumption” decreases the overall death rate and incidence and death rates from coronary artery disease, type 2 diabetes, and (probably) stroke. Drinking in moderation is defined as having “up to one drink per day for women and up to two drinks per day for men.” After swallowing an alcoholic drink, alcohol rapidly distributes in the total volume of water in the body; alcohol is insoluble so fatty tissues are spared. Women have more fat and smaller water volumes than men, which explains why women have higher blood alcohol concentrations after drinking the same amount of alcohol relative to their age and body weight. Aging decreases water volumes in women and men and raises blood alcohol levels higher than younger persons after equivalent intake. Aging also slows down the metabolism of alcohol, which keeps elderly drinkers tipsy longer than younger ones.

Chapter 16: Power of Exercise. Exercise is a type of physical activity in which planned, structured and repetitive bodily movements are performed, usually with the intent of improving physical fitness. The health benefits of physical activity-exercise are colossal and include strong evidence for lower risk of early death, coronary artery disease, stroke, high blood pressure, adverse lipid profile, type 2 diabetes, metabolic syndrome, and colon and breast cancers, plus the prevention of falls, improved muscular fitness, reduced depression, and better cognitive function in older adults. The benefits of physical activity-exercise are obvious, and free authoritative guidelines are available through the internet. Healthy adults do not need to see a doctor, but individuals unused to regular physical activity should start gently and gradually build up. Adults with chronic diseases should consult their physicians to plan a customized exercise schedule. Contradictions are few and obvious: recent heart disease and avoidance of exercise during flare-ups and fever. All Americans, young and old, should exercise regularly.

Chapter 17: Power of Nutrition. The latest Dietary Guidelines for Americans, 2010, stresses the importance of “consuming more of certain foods and nutrients such as fruits, vegetables, whole grains, fat-free and low-fat dairy products, and seafood,” and of consuming “fewer foods with sodium (salt), saturated fats, trans fat, cholesterol, added sugars, and refined grains.” But most Americans actually eat excessive amounts of unhealthy foods, like potato chips, French fries, sugar sweetened beverages, red meats, and processed meats, and not nearly enough healthy ones, such as vegetables, whole grains, fruits, nuts, and yogurt. The daily amount of sodium contained in ordinary table salt should be reduced to 2,300 mg for about half of all Americans and 1,500 mg for the other half, including people 51 and older and those with salt-susceptible disorders. Because fats and oils are important sources of calories, chose healthy mono- or polyunsaturated fats like olive, canola, corn, and peanut oils, and avoid saturated fats like cheese, beef, butter, whole milk, and trans fats.

Chapter 18: Self Help. Human skin takes a beating as people grow old, not only from the chronologic passing of years (intrinsic effects), but also from environmental wear and tear (extrinsic effects). To mitigate the extrinsic effects, the skin needs protecting from the 2 types of ultraviolet rays in sunlight, UVA and UVB, with a broad-spectrum sunscreen. Daily sleep time remains 7 to 9 hours during aging, but the phases of sleep become less constant, more fragmented, and shifts in timing (early to bed early to rise), and insomnia is more common. Especially troublesome and dangerous are multiple episodes of transient cessation of breathing (apnea), which may reduce levels of oxygen that disrupt brain function: most importantly obstructive sleep apnea. Mechanical breathing assistance is now standard treatment. Social activities are highly beneficial and broadly applicable. Antioxidants have a poor medical record and are not generally recommended. Vitamin and micronutrient supplements are recommended for pregnant women and those who intend to become pregnant and for people whose diets are deficient for whatever reason.

Chapter 19: Medical Help. Having regular checkups, vaccinations, and timely screening for treatable conditions to ward off complications before they occur are important elements of growing old. Preventive measures comprise a team effort: patients, family, friends, and doctors. Annual influenza vaccinations are strongly recommended for adults 65 and older, as are pneumococcal vaccinations every 5 years, a tetanus booster every 10 years, and a shingles vaccination now, if not already given. Recommendations for periodic screening tests of healthy adults at vulnerable ages include tests for circulating lipids, breast cancer, prostate cancer, colon cancer, lung cancer, and osteoporosis.

Chapter 20: Bad News Good News. Patient autonomy means that adults have the right to make decisions about their own medical care free from influences by doctors and other medical care providers; doctors provide advice and counsel, but patients have the final say as long as what they want is feasible and ethical. Given the relationship of mortal disease to advancing age, adults 50-years and older are strongly advised to talk to their family and physician about what they want the ends of their lives to be like. Then, these decisions should be formalized by an advance directive, which is often separated into two parts: a living will and a durable power of attorney for health care. In case a patient cannot make decisions unaided, the patient’s specified agent or surrogate, needs to transmit the patient’s wishes to the responsible physicians and make the documents available for confirmation. Increasing use of teams of home care specialists—expert at accommodating patient’s needs and wishes—and strengthened by palliative care professionals, has greatly improved end-of-life-care of increasing numbers of patients.