Why Can't a Man Be More Like a Woman?

by Wolpert, Lewis;

  However, a new theory has a different interpretation as to the cause of autism, and also the cause of psychotic disorders which are more common in women. Christopher Badcock has proposed that these disorders are based on the imprinted brain. As mentioned earlier, certain genes in the egg and sperm are imprinted during development and do not function. This new theory proposes that autism is due to a paternal bias in imprinted genes and that psychotic disorders are caused by a maternal bias in imprinted genes. Non-genetic factors such as nutrition in pregnancy can mimic and/or interact with imprinted gene expression, and the theory might even be able to explain the notable effect of maternal starvation on the risk of psychotic disorders as well as the ‘autism epidemic’ of modern affluent societies. Individuals with X-linked learning difficulties may also show this illness. An important example is Fragile X syndrome, expressed by forty-six per cent of males and sixteen per cent of females carrying a full mutation of a gene on the long arm of the X chromosome. Fragile X syndrome is the most common inherited cause of male intellectual disability and the best known single-gene cause of autism. It affects women rarely, and less severely.

  Dyslexia impairs verbal fluency, comprehension, and reading ability and is found about twice as often in boys than girls between the ages of seven and fifteen. The greater variance of reading performance in males may account in part for their higher number. Women are more frequently prone to persistent vocal problems when speaking or singing, regardless of their occupation.

  Many more boys than girls are affected by attention deficit and hyperactivity disorders. They are diagnosed twice to four times more often in boys than in girls. Attention deficit hyperactivity disorder–ADHD–is characterised by hyperactivity inattention and impulsivity. Overall, as Waddell and McCarthy have pointed out, males are more likely to suffer from disorders that occur early in development, such as hyperactivity disorders and learning disabilities, whereas females are more likely to develop mood disorders with later onset, such as depression. Critical periods of gonadal steroid release correspond to this difference in the onset of psychiatric disorders. It is, however, not yet possible to distinguish biological from societal and cultural influences on human brain development and behaviour. Waddell and McCarthy have also proposed, controversially, that males are at a higher risk for learning disabilities and hyperactivity because testosterone slows the early development of the brain, rendering males vulnerable to damage for longer periods of time. Aberrant developmental processes could occur during periods of dynamic embryological change in exposure to gonadal steroids. In males there is a perinatal sensitive period of elevated sex hormones that females do not experience, and this is a delicate period for brain development, when cellular processes like neuron differentiation and synapse formation could be affected.

  Phobias, or irrational fears, take many forms and an estimated ten million people in the United Kingdom suffer from this anxiety disorder. Simple phobias can be the fear of things like spiders, snakes, enclosed spaces, flying, heights, injections or even going to the dentist. Simple phobias usually start early in life, but more complex phobias like agoraphobia can be life restricting and usually develop later. About twice as many women as men meet criteria for any specific phobia, and three times as many fear spiders or snakes. Phobias can have an evolutionary origin and non-human primates have evolved a fear mechanism specifically for snakes and spiders. This fear can be elicited in the first year of human life, especially in females, probably through women’s historical exposure to these dangers while caring for their infants. Morbid fear of heights affects twice as many women as men.

  Anorexia nervosa, an eating disorder where sufferers have an obsessive fear of gaining weight, is ten times more common in females, probably influenced by living in a culture where thinness is an ideal. Research has suggested that the fact that ten times more women get the disease than men and the fact that the most common time for it to start is at puberty may be related to an abnormal response of the brain to appetite-suppressing effects of the female sex hormone oestrogen. Abnormal oestrogen receptors are more commonly found in women with the disorder. Bulimia is characterised by cycles of eating too much in a short period of time–often in secret. It is also ten times more common in women. Individuals with bulimia alternate between bouts of excessive eating followed by periods of purging, with vomiting or the use of laxatives. The causes are not understood but again there may be a hormonal influence, since testosterone seems to protect men against eating disorders. Twin studies have shown that females who were in the womb with male twins have a lower risk for eating disorders than females with female twins, which suggests that testosterone from their male twin may protect them. Another illustration of sex difference is that exposure to severe malnutrition by children aged eleven to fourteen in the Dutch famine of 1944 made it much more likely that the females would develop diabetes and/or peripheral arterial disease at ages sixty to seventy-six, but that men did not have the same risk.

  Sleep is another area where women may suffer more than men. Before puberty there are no significant differences between boys and girls, but adult women are twice as likely as men to have difficulties either falling asleep or staying asleep. One survey showed that seventy-eight per cent of women claimed not to have had a full night’s sleep in the previous twelve months. Hormonal factors during pregnancy, lactation and menopause may lead to insomnia as well as psychological issues like depression or pain syndromes, which are both found more commonly in women.

  Turning now to physical illnesses, cardiovascular disease is the most common cause of death in men and women worldwide. In the United Kingdom around one in six men and one in nine women die from it, says the British Heart Foundation. The incidence and the progression of cardiovascular disease and hypertension are much higher in men than in pre-menopausal women of the same age. But after menopause this is no longer true, and the incidence and rate of progression are similar. So men may develop most cardiovascular diseases, though not all of them, at an earlier age than women, but the number of affected women significantly increases with age.

  Biological explanations for differences in the physical health of women and men often focus on the role of sex hormones. For example, oestrogen may protect premenopausal women from cardiovascular disease but may contribute to more women suffering from autoimmune disorders and pain conditions. It has been shown by Nadkarni and colleagues that this female sex hormone has an effect on white blood cells by moving a protein–annexin–from the surface of the cell into the interior, and thus preventing the cells from sticking to the insides of blood vessels, and causing dangerous blockages. Lower oestrogen levels after the menopause may be one reason why cardiovascular disease rates increase in women later in life and why these rates are higher throughout life in men. Oestrogen administration in postmenopausal women (HRT) has been associated with a significant reduction in the development of coronary artery disease and stroke. This has been interpreted as evidence that women’s reproductive hormones give them protection them from these conditions. But the exact molecular mechanisms underlying this process have yet to be discovered and it may be that some differences are mediated by other mechanisms, especially by products of genes located on the X and Y chromosomes.

  An important set of biological differences affecting health are sex-related differences in the nervous system’s control of the heart. These may appear in measurements of heart-rate variability during the performance of a simple hand-grip motor task. Other differences may be seen in the relationship between regional blood flow and parasympathetic nervous activity which makes it possible for the body to recuperate and return to a balanced state. Females show an increased blood flow in the amygdala in response to parasympathetic activity whereas males show a reduction.

  In heart failure risk factors and changes in heart muscle differ in men and women. A gene has been identified in one in five men, inherited from the father, which increases their risk of heart disease by fifty per cent. Women’s heart m
uscle has been found to remodel itself more effectively after injury than that of men. This may be related to the sex hormones, that is, oestrogens and testosterone. Clinical analysis of the differences in disease of the heart valves supports this hypothesis. Clinical management in advanced countries differs between the sexes, with under-diagnosis and under-treatment typically being applied to women. But despite this, women frequently survive better than men. Men have a higher incidence of atrial fibrillation–an irregular heartbeat–than women. Lack of exercise is associated with an increased risk of heart disease in men, but surprisingly studies of women have produced mixed results. It seems that men who increase their level of activity can decrease their risk of heart disease, but this is not true for women. Diller, Patros and Prentice found differences in cardiovascular reactivity between the sexes in response to stress, as females tend to have greater heart-rate responses and males tend to have greater changes in blood pressure. As we have seen, women generally have better cardiac function and survival than men. However, it remains unclear whether there are sex differences in clinical features, treatment and prognosis after acute heart attacks. Some studies have reported no significant difference in mortality after adjusting for differences in age and other risk factors. Dreyer and her colleagues found that women with stable angina do worse than their male counterparts, and that several factors may contribute to this. These include clinical management, underlying biology and psychosocial issues.

  Obesity is a growing problem, particularly in the United States and the United Kingdom, and both sexes carry risks. In 2012 in England twenty-five per cent of people, both men and women, were classified as obese by the NHS. But obese men may carry greater overall health risks, including risks for heart disease, than women. This is because more of them tend to carry the excess weight around their waist, rather than distributed in their hips and thighs, and are ‘apple’- rather than ‘pear’-shaped.

  Autoimmune diseases include more than seventy different disorders caused by the antibodies whose normal role is to prevent infections from bacteria and viruses attacking the body. These diseases are overwhelmingly expressed in women, with over eighty per cent of patients being female. Very few autoimmune disorders show a male predominance. Although the evolutionary origin of the sexual immune difference is still unclear, it may be that women have a stronger immune system to save them from infections. This could be due to their role creating new life, thus requiring a stronger immune system to protect themselves so they can nurture the offspring. Type 1 diabetes, though an autoimmune illness, does not show an increased prevalence in women and is the only common organ-specific autoimmune disorder not to show a strong female bias.

  Multiple sclerosis is a severe autoimmune illness affecting more than twice as many women as men. Worldwide there are more than 2.3 million sufferers. It is caused by the sufferer’s own antibodies destroying the cells that insulate the axons of neurons, causing a failure to transmit nerve impulses, and symptoms can occur in any part of the body. There are many different symptoms, the most common ones including numbness and tingling, problems with mobility and balance, muscle weakness and tightness and blurred vision.

  Primary biliary cirrhosis is an autoimmune disease of the liver which has a nine-to-one female predominance. The main immunological characteristic of the illness is an antibody to mitochondria, the intracellular organelles which produce energy. This antibody cross-reacts with a product found in cosmetics, soaps and perfumes, and Lockshin has argued that lifestyle choices that are predominantly female, such as use of cosmetics and perfumes, lead to the development of this highly female-predominant disorder. The sex ratios of other autoimmune diseases are similarly more likely to be explained by environmental exposure than by intrinsic biological differences, he says.

  Chronic fatigue syndrome, more common in women, is characterised by severe fatigue and headache, tender lymph nodes, joint and muscular pain, and an inability to concentrate. It may be related to the immune system, but this remains controversial. Women are also more likely than men to develop rheumatoid arthritis, a chronic systemic inflammatory disorder that principally attacks joints. The disease often leads to the destruction of cartilage as it progresses, and causes severe stiffness and pain in the joints. It is known that autoimmunity plays a key role in causing rheumatoid arthritis, but exactly what triggers the attack is unknown. About one per cent of the world’s population is afflicted by rheumatoid arthritis, and for every man three women are sufferers. Recent data suggest that women also suffer greater disability than men with this disease. Women have stronger natural inflammatory responses than men when their immune systems are triggered. But although this may often result in superior immunity, if the immune system goes wrong it may also increase a woman’s risk of developing an autoimmune disorder.

  With stroke, a part of the brain dies from lack of blood. Globally stroke is more common among men, but women are more severely incapacitated. A factor causing stroke may be raised blood pressure, found to be higher in men than in women of similar ages. When men and women of the same age are compared, more men than women suffer strokes. But this difference vanishes in old age. Treatments also vary. Men are treated more often with intravenous thrombolysis, which causes the breakdown of blood clots by injection of pharmacological agents, compared with women. Aspirin seems more effective in reducing risk in men than in women, but statins have a similar effect in both sexes.

  Cancer affects more men than women, and men are more likely than women to die from it. The two most common cancers are prostate cancer and breast cancer. The incidence of breast cancer in the United Kingdom is about 49,000 cases a year; for prostate about 41,000. The three cancers that affect only men are penile, prostate and testicular cancer. For men the three major killers are lung, prostate and bowel cancers, and for women, lung, breast and bowel. The incidence of lung cancer is greater in men than in women. In 2010 nearly 19,000 women were diagnosed with lung cancer in the UK, compared to 23,000 in men. Unlike men, the majority of women who develop lung cancer have never smoked.

  For infectious diseases, in most settings, tuberculosis is more common in males at all ages except in childhood, when the reverse is the case. Only a third of the world’s reported TB cases are in women. Malaria is equally likely to be contracted by men and women but pregnant women are at greater risk. The increased risk of seasonal and pandemic influenza to pregnant women and the elderly has been well documented. When women have a chronic cough they are more likely to go to the doctor than men, partly because they may also suffer from embarrassing complications such as stress incontinence. HIV is much more common among men owing both to their heterosexual and to their homosexual sexual activity.

  Some sex differences in illness change with age. The common diseases of older men and women are similar, namely heart disease, cancer, musculoskeletal problems, diabetes, mental illness, impairments of sight and hearing, and incontinence. As we have seen men develop cardiovascular disease earlier than women. There are clear differences in health in old age between the sexes. Although women may have heart attacks later than men, they also tend to have a poorer quality of later life as a result of both physical limitations and depression. Osteoporosis, which is characterised by loss of bone mass leading to increased risk of fracture, affects around three million people in the United Kingdom. Women more often develop primary osteoporosis, which is related to the drop in oestrogen that occurs at menopause as a normal part of the ageing process.

  According to brain-imaging studies, memory and attention deficits in ageing are related to a reduction of grey matter and to decreased activity in frontal and mediotemporal areas. There are no sex differences in the ageing of white matter, but the steepness of the trajectory along which grey matter volume decreases differs between men and women in almost all regions. There are greater age-related overall declines in brain volume in men than in women, possibly resulting in greater age-related overall losses of cognitive functioning. But findings are inconsistent.
Several studies have reported older men to have outperformed their female controls in mental speed tasks. This result stands in contrast to results for memory, which favour women and illustrates the multidimensionality of cognition. However, these findings remain equivocal. There is also the suggestion that the best way to get a man to do something is to tell him he is too old for it!

  One study in the United Kingdom carried out on 11,000 men and women aged over fifty and published as part of the Longitudinal Study on Ageing in 2010 found that women aged seventy-five and older reported a particularly low standard of well-being with many symptoms of depression, low life satisfaction, poor quality of life and high ratings of loneliness. In contrast men aged sixty-five and over seemed to be more satisfied with their lives than younger men. The researchers suggest that women affected by loneliness feel a greater sense of isolation when children leave home or when husbands, partners and friends are no longer around. Professor Sir Michael Marmot, lead researcher on the UK study, said: ‘Older women are more likely to be living lives of loneliness because men die earlier.’

  After their role in embryonic development, hormones continue to have important effects. Testosterone affects emotional tone and cognition. As women age, neurobehavioural functions such as sexual arousal or aggression decrease and the ratio of testosterone to oestrogen increases. For men, the reverse is true. Beginning at approximately fifty, men secrete progressively lower amounts of testosterone; about twenty per cent of men aged over sixty have lower than normal levels, and so the ratio of oestrogen to testosterone increases.