Spark

by John J. Ratey

Exercise seems to be more than just not harmful, though. In one study, Clapp compared thirty-four newborns of exercisers to thirty-one of sedentary mothers five days after birth. There’s only so much you can do to gauge behavior at this early stage, but the babies from the exercise group “performed” better on two of six tests: they were more responsive to stimuli and better able to quiet themselves following a disturbance of sound or light. Clapp sees this as significant because it suggests that infants of exercising mothers are more neurologically developed than their counterparts from sedentary mothers. He theorizes that physical activity jostles the baby in the womb, providing stimulation not unlike the effects of touching and holding newborns, which clearly improves brain development. In another comparison at five years of age, he found no differences in behavior and most cognitive measures, but there were statistically significant differences in IQ and oral language skills. The children of exercisers performed better, and his unpublished observations suggest that years later their academic performance is better than kids whose moms were inactive, which is amazing.

Stacy had lifted weights occasionally, but as I explained to her and Tony, aerobic exercise is different—and crucial for mood. Now she spends forty-five minutes on her elliptical trainer almost every night. If she misses it for more than a few days, she has trouble sleeping and notices a drop in energy and mood. Does that mean she’s still depressed and just masking it with exercise? Not exactly. It’s just that if symptoms flare up, as they sometimes do during her period, she hits the trainer to make sure they don’t snowball into something worse. Above all, she knows she can handle it. “If I exercise, I’m fine,” she says. “I feel like I’m back to normal.”

Statistically, fit mothers have a lower incidence of depression. In one survey of one thousand women in the South of England six weeks after childbirth, the 35 percent who reported doing vigorous exercise three times a week had significantly fewer mood problems. They also had lost more weight, stayed more socially active, and felt more confident and satisfied in being mothers. An exercise routine can help new moms reestablish control over their lives and keep them from feeling overwhelmed. It also provides a great way for them to take time for themselves, which is important in staving off resentment. Like Stacy, about 70 percent of women are dissatisfied with their bodies at six months after childbirth, and obviously exercise can get them back in shape and boost self-image. Unfortunately, the message that exercise provides something more than physical redemption has been slow to reach doctors and their patients. “People think of exercise in terms of physical health, but not mental health,” says Jennifer Shaw, an obstetrician-gynecologist in Brookline, Massachusetts, who is a clinical instructor at Harvard Medical School. “It’s difficult as a physician to get people to take exercise seriously, as a treatment that actually has medical benefits aside from taking off the pounds.”

The great value of exercise for women beyond menopause is that it helps balance the effects of diminished hormones, and as you’ll see in the following chapter, it protects against cognitive decline. From an evolutionary perspective, exercise tricks the brain into trying to maintain itself for survival despite the hormonal cues that it is aging.

It’s well established that more women suffer from Alzheimer’s disease than men, even when the statistics are adjusted for the fact that women live longer. On the other hand, the protective effects of exercise on cognitive decline seem to be magnified among women. In a 2001 study published in the Archives of Neurology, Danielle Laurin of Quebec’s Laval University analyzed the relationship between exercise and physical activity among a group of 4,615 elderly men and women over the course of five years. Laurin found that women over sixty-five who reported higher levels of physical activity were 50 percent less likely than their inactive peers—women and men alike—to develop any form of dementia.

ESTABLISH A ROUTINE At least four days a week, I suggest getting out there and walking briskly or jogging or playing tennis or engaging in some form of activity that will get your pulse up to 60 to 65 percent of your maximum heart rate. You want to keep it there for an hour. People always want to know what type of aerobic activity is best, and the answer is whatever is going to allow you to build it into your lifestyle. The important thing is to stick with it, and make sure you’re elevating your heart rate enough to get the benefits. It’s also important to mix in strength training a couple of days a week, to shore up your bones against osteoporosis.

For younger women with PMS, I would suggest five days a week of aerobic exercise at the same level, but it might be a good idea to mix in more intense bursts like sprinting on two of those days, though not back-to-back. Some of the studies suggest that higher intensity effort has a more dramatic effect on symptoms such as irritability, anxiety, depression, and mood instability. And if your symptoms are particularly bad, and you’re not completely sidelined with cramps, it’s probably a good idea to do something every day during the premenstrual phase of your cycle.

The advice that surprises people the most, I think, is that it’s important to keep up exercise during pregnancy, a recommendation that has finally been endorsed by the American College of Obstetricians and Gynecologists. Its guidelines specify thirty minutes of moderate-intensity aerobic activity every day during pregnancy for healthy women. Obviously, it’s important to get clearance directly from your obstetrician, but it’s safe for most women. Likewise, I can’t stress enough the importance of picking up your routine as soon as possible after the baby is born, ideally within a few ...

In 1900, the average American could expect to live to age forty-seven. Today, life expectancy is over seventy-six, and when older folks die, the reason is more likely to be chronic disease than acute illness. But those who outlive these odds face other daunting statistics: The average seventy-five-year-old suffers from three chronic medical conditions and takes five prescription medicines, according to the Centers for Disease Control (CDC). Among those over sixty-five, most suffer from hypertension; more than two-thirds are overweight; and nearly 20 percent have diabetes (which triples the chance of developing heart disease). The leading killers are heart disease, cancer, and stroke; together they account for 61 percent of all deaths in this age group.

We already know that smoking, inactivity, and eating poorly are root causes of these bodily diseases. Likewise, the latest research is clear about how lifestyle influences the mental hazards that come with aging. The same things that kill the body kill the brain, which neuroscientist Mark Mattson, of the National Institute on Aging, sees as a positive. “I think the good news—if we take it seriously—is that many of the same factors that can reduce our risk for cardiovascular disease and diabetes also reduce the risk for age-related neurodegenerative disorders,” he says. The measures we would take to guard against diabetes, for example, also balance insulin levels in the brain and shore up neurons against metabolic stress. Running to lower our blood pressure and strengthen our heart also keeps the capillaries in the brain from collapsing or corroding and causing a stroke. Lifting weights to prevent osteoporosis from devouring our bones releases growth factors that make dendrites bloom. Conversely, taking omega-3 fatty acids for mental acuity strengthens our bones.

The mental and physical diseases we face in old age are tied together through the cardiovascular system and metabolic system. A failure of these underlying connections explains why people who are obese are twice as likely to suffer from dementia, and why those with heart disease are at far greater risk of developing Alzheimer’s, the most common form of dementia. Statistically, having diabetes gives you a 65 percent higher risk of developing dementia, and high cholesterol increases the risk 43 percent. We’ve had the medical proof that exercise protects against these diseases for decades, yet, according to the CDC, about a third of the population o...

People like my mother who stay involved and active as they age can slow down the degeneration. In one study of recent retirees, researchers found that those who exercised maintained nearly the same level of blood flow in the brain after four years, while the inactive group had a significant decrease. If your brain isn’t actively growing, then it’s dying. Exercise is one of the few ways to counter the process of aging because it slows down the natural decline of the stress threshold. “Paradoxically,” says Mattson, “it’s good that cells be periodically subjected to mild stress because it improves their ability to cope with more severe stress.”

The major implication is that exercise not only keeps the brain from rotting, but it also reverses the cell deterioration associated with aging. More than likely, what Kramer’s scans show is how exercise improves the brain’s ability to compensate. “Let’s say the prefrontal cortex isn’t functioning quite up to par,” he explains. “You might be able to recruit other areas of the cortex to do the task in a different way. One way to think about the increased volume is that it might turn back the clock in terms of how well the circuits function to do different things.” There’s an awful lot our brains can do with an extra two to three years.

I have faith that when people come to recognize how their lifestyle can improve their health span—living better, not simply longer—they will, at the very least, be more inclined to stay active. And when they come to accept that exercise is as important for the brain as it is for the heart, they’ll commit to it. Here’s how exercise keeps you going: 1. It strengthens the cardiovascular system. A strong heart and lungs reduce resting blood pressure. The result is less strain on the vessels in the body and the brain. There are a number of mechanisms at work here. First, contracting muscles during exercise releases growth factors such as VEGF and fibroblast growth factor (FGF-2). Aside from their role in helping neurons bind and promoting neurogenesis, they trigger a molecular chain reaction that produces endothelial cells, which make up the inner lining of blood vessels and thus are important for building new ones. These inroads expand the vascular network, bringing each area of the brain that much closer to a lifeline and creating redundant circulation routes that protect against future blockages. Second, exercise introduces more nitric oxide, a gas that widens the vessels’ passageways to boost blood volume. Third, the increased blood flow during moderate to intense activity reduces hardening of the brain arteries. Finally, exercise can to some extent counteract vascular damage. Stroke victims and even Alzheimer’s patients who participate in aerobic exercise improve their sco...

DIET: EAT LIGHT, EAT RIGHT The one proven way to live longer is to consume fewer calories—at least if you’re a lab rat. In experiments in which rodents eat 30 percent fewer calories, they live up to 40 percent longer than animals allowed to eat as much as they want. “Our control group is really overfed and underexercised,” says neuroscientist Mark Mattson, pointing out that group is “a good match for a lot of the American population.” A study in monkeys that began eighteen years ago in the experimental gerontology lab at the National Institute on Aging suggests the same holds true in primates. And one human trial showed that asthma patients on a restricted diet for two months—three meals one day and only five hundred calories the next—had fewer markers of oxidative stress and inflammation in their blood (and their asthma symptoms improved). This finding supports the theory that imposing mild stress on the cells—in this case depriving them of fuel—makes them more resilient to future challenges and reduces free radicals. “It’s kind of like exercising for an hour every day,” Mattson says. “It’s a mild stress, but as long as there’s a recovery period, it’s good.” He is cautious about telling people to skip meals, but that’s what he does: no breakfast, a salad for lunch, and a normal dinner, for a total of about two thousand calories. It’s likely that people of normal weight wouldn’t benefit as much, and anyone over fifty should be careful about malnourishment because they’re l...

Your overall strategy should include four areas: aerobic capacity, strength, and balance and flexibility. You should consult with a doctor or trainer who knows your history, but I can give you some solid guidelines. AEROBIC. Exercise four days a week, varying from thirty minutes to an hour, at 60 to 65 percent of your maximum heart rate. At this level, you’ll be burning fat in the body and generating the ingredients necessary for all the structural changes in the brain I’ve discussed. Walking should be perfectly adequate, but do it outside with a friend if possible. Whatever you choose, try to find something that you will enjoy over the long haul. Try a more intense pace for two days a week—70 to 75 percent of your maximum—for twenty to thirty minutes. If you haven’t been exercising, you’ll want to build up to this speed, and that’s fine. Consistency is probably more important than intensity. “You don’t have to work as hard as you may think you do,” suggests Kramer. “If you can work harder and run rather than walk, that’s great. But if you can’t, walking is what we’ve looked at, and it can have some fairly dramatic effects.” STRENGTH. Hit the weights or resistance machines twice a week, doing three sets of your exercises at weights that allows you to do ten to fifteen repetitions in each set. This is critical for preventing and counteracting osteoporosis: even if you do all the aerobic training in the world, your muscles and bones will still atrophy with age. A Tufts Unive...

MENTAL EXERCISE: KEEP LEARNING My advice here is to keep challenging your mind. You know by now that exercise prepares your neurons to connect, while mental stimulation allows your brain to capitalize on that readiness. It’s no coincidence that study after study shows that the more education you have, the more likely you are to hang onto your cognitive abilities and stave off dementia. But it’s not necessarily about the diploma. It’s just that those who have spent a lot of time in school are more likely to remain interested in learning. Tucked within those statistics are plenty of people who didn’t go to college yet nurture intense interests in the world around them.

There was a nun named Sister Bernadette who died of a heart attack at age eighty-five in the mid-1990s. Along with more than six hundred other nuns, she donated her brain to science as part of an ongoing study conducted by epidemiologist David Snowdon, who memorialized the School Sisters of Notre Dame, in Mankato, Minnesota, in his inspiring book, Aging with Grace. The nuns constantly challenge their minds, with vocabulary quizzes, mental puzzles, and debates about public issues, and many of them live to be one hundred or more. The interesting thing about Sister Bernadette is that she scored in the ninetieth percentile on cognitive tests right up until she died, but when her brain was examined postmortem, it showed massive damage from Alzheimer’s disease. Tissue from her hippocampus to her cortex was riddled with plaque and neurofibrillary tangles to the most extensive degree, and she also carried the ApoE4 gene variant. In other words, she should have been utterly lost to the ravages of dementia. Yet despite the damage in her brain, she remained mentally sharp. Snowdon points to the notion of cognitive reserve as a possible explanation. This is the brain’s ability to adapt and compensate for damage by recruiting other areas to help with tasks. By teaching until a late age and staying mentally active, Sister Bernadette almost certainly trained her brain to work around the genetic hand she was dealt. Her example, like that of my mother, is one to live by.

Quite simply, we need to engage our endurance metabolism to keep our bodies and brains in optimum condition. The ancient rhythms of activity ingrained in our DNA translate roughly to the varied intensity of walking, jogging, running, and sprinting. In broad strokes, then, I think the best advice is to follow our ancestors’ routine: walk or jog every day, run a couple of times a week, and then go for the kill every now and then by sprinting. Your choices aren’t limited to these modes of aerobic activity, naturally, but I think they’re helpful categories to distinguish between low-intensity (walking), moderate-intensity (jogging), and high-intensity (running) exercise. If you want to make the most of your time and effort, you’ll need a way to accurately judge your level of exertion along these divisions. When I talk about walking, or low-intensity exercise, I’m referring specifically to exercising at 55 to 65 percent of your maximum heart rate. By my definition, moderate intensity falls in the range of 65 to 75 percent, while high intensity is 75 to 90 percent. The upper end of high-intensity exercise is sometimes painful but always powerful territory that has gained a lot of scientific interest recently.

Duscha is an expert in cardiovascular health, but he says the same thing almost every neuroscientist cited in these pages has said: “A little is good, and more is better.” The best, however, based on everything I’ve read and seen, would be to do some form of aerobic activity six days a week, for forty-five minutes to an hour. Four of those days should be on the longer side, at moderate intensity, and two on the shorter side, at high intensity. And while there’s conflicting evidence about whether high-intensity activity, which can force your body into anaerobic metabolism, impacts thinking and mood, it clearly releases some of the important growth factors from the body that build up the brain. So, on the shorter, high-intensity days, include some form of strength or resistance training. These days should not be back to back; your body and brain need recovery time to grow after high-intensity days. In total, I’m talking about committing six hours a week to your brain. That works out to 5 percent of your waking hours.