Inferior: How Science Got Women Wrong – and the New Research That’s Rewriting The Story. Angela Saini

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СКАЧАТЬ 1800 life expectancy at birth in Sweden stood at thirty-three years for women and thirty-one for men. In 2015 it was around eighty-three for women and around seventy-nine for men. ‘Women are more robust than men. I think there’s little doubt about that,’ Austad says. ‘It was true in the eighteenth century in Sweden, and it’s true in the twenty-first century in Bangladesh, and in Europe, and in the US.’

      I ask Austad whether women might be naturally outliving men for social reasons. It’s reasonable to think, for instance, that boys are generally handled more roughly than girls are. Or that more men than women take on risky jobs, such as construction and mining, which also expose them to toxic environments. And we know that in total across the world, far more men than women smoke, which dramatically pushes up mortality rates. But Austad is convinced that the difference is so pronounced, ubiquitous and timeless that it must mean there are features in a woman’s body that underlie the difference. ‘It’s hard for me to imagine that it is environmental, to tell you the truth,’ he says.

      The picture of this survival advantage is starkest at the end of life. The Gerontology Research Group in the United States keeps a list online of all the people in the world that it has confirmed are living past the age of 110. I last checked the site in July 2016. Of all these ‘supercentenarians’ in their catalogue, just two were men. Forty-six were women.

      Yet we don’t know why.

      ‘I’m absolutely puzzled by it,’ says Austad. ‘When I first started looking into this, I expected to find a huge literature on it, and I found virtually nothing. There’s a big literature on “Is this a difference between men and women?”, but the underlying biology of the survival difference, there’s very little on that. It’s one of the most robust features of human biology that we know about, and yet it’s had so little investigation.’

      For more than a century, scientists have painstakingly studied our anatomy, even collected thousands of litres of horse urine in their attempts to isolate the chemicals that make men more masculine and women more feminine. Their search for sex differences has had no boundaries. But when it comes to why women might be more physically robust than men – why they are better survivors – research has been scarce. Even now, only scraps of work here and there point to answers.

      ‘It’s a basic fact of biology,’ observes Kathryn Sandberg, director of the Center for the Study of Sex Differences in Health, Aging and Disease at Georgetown University in Washington, DC, who has explored how much of a role disease has to play in why women survive. ‘Women live about five or six years longer than men across almost every society, and that’s been true for centuries. First of all, you have differences in the age of onset of disease. So, for example, cardiovascular disease occurs much earlier in men than women. The age of onset of hypertension, which is high blood pressure, also occurs much earlier in men than women. There’s also a sex difference in the rate of progression of disease. If you take chronic kidney disease, the rate of progression is more rapid in men than in women.’ Even in laboratory studies on animals, including mice and dogs, females have done better than males, she adds.

      By picking through the data, researchers like her, Joy Lawn and Steven Austad have come to understand just how widespread these gaps are. ‘I assumed that these sex differences were just a product of modern Westernised society, or largely driven by the differences in cardiovascular diseases,’ says Austad. ‘Once I started investigating, I found that women had resistance to almost all the major causes of death.’ One of his papers shows that in the United States in 2010, women died at lower rates than men from twelve of the fifteen most common causes of death, including cancer and heart disease, when adjusted for age. Of the three exceptions, their likelihood of dying from Parkinson’s or stroke was about the same. And they were more likely than men to die of Alzheimer’s Disease.

      When it comes to fighting off infections from viruses and bacteria, women also seem to be tougher. ‘If there’s a really bad infection, they survive better. If it’s about the duration of the infection, women will respond faster, and the infection will be over faster in women than in men,’ says Kathryn Sandberg. ‘If you look across all the different types of infections, women have a more robust immune response.’ It isn’t that women don’t get sick. They do. They just don’t die from these sicknesses as easily or as quickly as men do.

      One explanation for this gap is that higher levels of oestrogen and progesterone in women might be protecting them in some way. These hormones don’t just make the immune system stronger, but also more flexible, according to Sabine Oertelt-Prigione, a researcher at the Institute of Gender in Medicine at the Charité University Hospital in Berlin. ‘This is related to the fact that women can bear children,’ she explains. A pregnancy is the same as foreign tissue growing inside a woman’s body that, if her immune system was in the wrong gear, would be rejected. ‘You need an immune system that’s able to switch from pro-inflammatory reactions to anti-inflammatory reactions in order to avoid having an abortion pretty much every time you get pregnant. The immune system needs to have mechanisms that can, on one side, trigger all these cells to come together in one spot and attack whatever agent is making you sick. But then you also need to be able to stop this response when the agent is not there any more, in order to prevent tissues and organs from being harmed.’

      The hormonal changes that affect a woman’s immune system during pregnancy also take place on a smaller scale during her menstrual cycle, and for the same reasons. ‘Women have more plastic immune systems. They adapt in different ways,’ says Oertelt-Prigione. Many types of cell in the body are involved in immunity, but the kind that come into closest contact with viruses and bacteria are known as T cells. They inject substances into bacteria to kill them, or secrete other substances that call more cells to action, some of which ‘eat up’ infected cells and bacteria, like Pac-Man in the video game, she explains. Researchers know that a certain type of T cell that’s crucial to managing the body’s response to infections becomes more active in the second half of a woman’s menstrual cycle, when she’s able to get pregnant.

      The discovery that sex hormones and immunity might be linked is fairly recent. In men, scientists have explored connections between testosterone and lower immunity, although the evidence is relatively thin. In 2014, for example, Stanford University researchers found that males with the highest levels of testosterone had the lowest antibody response to a flu vaccine, which meant they were the least likely to be protected by the jab. As yet, though, it’s an unsubstantiated link. In women, the connection is far clearer. So much so that patients themselves have noticed these fluctuations. For years, doctors assumed that a woman’s immunity didn’t change during her menstrual cycle. If she did report a difference in pain levels, doctors might dismiss it as premenstrual syndrome, or some vague psychological complaint. It was only when these links were increasingly backed up by hard research that scientific interest was sparked, and more research began to flourish.

      This problem runs all the way through research into women’s health. If a phenomenon affects women, and only women, it’s all too often misunderstood. And this is compounded by the fact that even though they’re better at surviving, women aren’t healthier than men. In fact, quite the opposite.

      ‘If you could add up all the pain in the world, all the physical pain, I suspect that women have way, way more of it. This is one of the penalties of being a better survivor. You survive, but maybe not quite as intact as you were before,’ says Steven Austad. Statistically, this could explain why women seem proportionally sicker than men. ‘Part of the reason that there are more women than men around in ill health is to do with the fact that women have survived events that would kill men, and so the equivalent men are no longer with us.’

      Another reason is that women’s immune systems are so powerful that they can sometimes backfire. ‘You start regarding yourself as foreign, and your immune system starts attacking its own cells,’ explains Kathryn Sandberg. Diseases caused in this way are known as autoimmune disorders. The most common include rheumatoid arthritis, lupus СКАЧАТЬ