IELTS Academic Reading Practice Test 350

In 1948, a small town in Massachusetts became the setting for an experiment that would reshape the way medicine thinks about the human heart. Framingham was then a manufacturing centre of some 28,000 people, chosen by researchers not for any unusual quality but precisely because it was ordinary: its workforce was stable, its population was large enough for statistical purposes, and its doctors were willing to cooperate. The project that began there was conceived in an atmosphere of frustration. Doctors could recognise the symptoms of heart disease well enough, but they had almost no idea what brought it on, and the advice they gave patients rested largely on guesswork.

Before the Second World War, the study of chronic disease was dominated by the search for a single cause. If a patient developed a condition, the reasoning went, some agent — a germ, a toxin, a deficiency — must be responsible, and once it was identified the disease could be conquered. Tuberculosis and diphtheria seemed to confirm this model. Heart attacks and strokes, however, did not fit it. They appeared in people with no obvious infection, and their frequency seemed to rise as populations grew wealthier and more sedentary, a pattern that the germ theory could not explain.

The idea of following a large group of healthy people over many years, recording everything that happened to them and looking afterwards for differences between those who became ill and those who did not, was already established in epidemiology, but it had rarely been applied to diseases of the heart. The Framingham study, funded by the newly created National Heart Institute, enrolled about 5,200 adults between the ages of thirty and sixty-two. Every two years they came to a clinic for a physical examination, blood tests, and questions about smoking, diet, occupation and exercise. The commitment demanded of the volunteers was considerable, and the town's residents were kept informed through local meetings and newspaper reports.

The first results, published in the late 1950s and early 1960s, were startling. Cholesterol measured in the blood, cigarette smoking and high blood pressure each predicted the likelihood of a heart attack, and their effects appeared to combine rather than simply add together. The study also gave a name and a measure to what had been a vague notion: the risk factor. The concept was genuinely new. It meant that a healthy person could carry an elevated probability of future illness and that this probability could be estimated with numbers, argued about, and in principle reduced.

Framingham's contribution went further than any single finding. The study produced the first widely used risk equations, which combined several measurements into a single estimate of the chance of a heart attack within a stated period. It helped establish the link between physical inactivity and coronary disease, and it documented the dangers of raised blood pressure, which many physicians had previously regarded as a harmless consequence of ageing. The finding that high blood pressure mattered was resisted for years in some clinical circles, but the accumulating evidence eventually changed practice.

By the 1970s the study's findings had begun to influence public policy. Officials in the United States and elsewhere cited the evidence on smoking and blood pressure when they introduced health warnings, screening programmes and campaigns encouraging exercise. Deaths from coronary heart disease in the United States, which had risen through the middle of the century, began to fall from the late 1960s. No single measure can be credited with that decline, but the intellectual foundation for prevention had been laid in Framingham.

The design of the study was altered substantially over time. The original participants were followed for the rest of their lives, and in 1971 their adult children and spouses were enrolled as the Framingham Offspring Study, with a third generation joining from 2002. This generational approach allowed researchers to ask questions the original cohort could not answer: how strongly does heart disease run in families, and how do inherited tendencies interact with behaviour?

The study has also been criticised, fairly, for its composition. Its volunteers were overwhelmingly of European descent, and for decades its conclusions were applied to everyone. Later research has shown that risk factors operate somewhat differently in other populations, and the study's own investigators have acknowledged the limitation.

The study's methods have also been refined in ways its founders could not have foreseen. Observational research of this kind can reveal associations, but it cannot by itself prove that one thing causes another, because people who differ in one habit usually differ in others as well. The decades since Framingham contain several cautionary examples in which advice based on large observational studies was later revised when randomised trials produced different answers, most famously in the case of hormone replacement therapy after the menopause.

The town itself has occasionally been uneasy about its role. Residents have complained that their health is discussed in public and that they are asked to give blood too often, yet participation has remained high across three generations. Perhaps the most durable legacy is a change in the way ordinary people talk about their own bodies. Terms that were once confined to medical journals — cholesterol, blood pressure, risk factor — are now part of everyday conversation, and the idea that a person can take steps to lower their chances of a heart attack is accepted almost everywhere.

A human body replaces its cells constantly. The lining of the gut is renewed every few days, red blood cells last about four months, and even the liver can regenerate after injury. Yet the organism as a whole declines, and it does so in ways that are remarkably consistent between individuals. Gerontologists — researchers who study ageing — now describe this decline not as a single process but as a collection of interacting ones, often called the hallmarks of ageing. Among the most intensively studied are the shortening of chromosome ends, the accumulation of damaged proteins, and the behaviour of cells that have stopped dividing.

Much attention has focused on telomeres, the repetitive sequences of DNA that cap the ends of chromosomes. Because the machinery that copies DNA cannot finish the very end of a strand, each division shortens the telomere slightly. When it becomes critically short, the cell stops dividing and enters a state called senescence. Telomerase, an enzyme discovered in the 1980s, can rebuild telomeres, and it is active in sperm cells, in some stem cells and in most cancers. In ordinary body cells it is largely switched off, which is one reason why human tissues have a limited capacity for renewal.

The obvious inference is that lengthening telomeres should slow ageing, and a large industry has grown up around that idea. The biology is less obliging. Mice engineered to lack telomerase age prematurely, and in some experiments mice given extra telomerase lived longer, but in others the extra enzyme increased the incidence of tumours. Human genetic studies have linked unusually short telomeres to several age-related diseases, yet the causal direction is uncertain: illness may shorten telomeres as readily as short telomeres may cause illness. Telomere length also varies enormously between healthy people of the same age, which makes it a poor individual predictor.

Senescent cells have proved a more promising target. These are cells that have permanently withdrawn from the cell cycle but remain alive, releasing a mixture of inflammatory signals and enzymes that affect neighbouring tissue. The phenomenon was first described in the 1960s by Leonard Hayflick, who showed that human cells grown in culture divide a limited number of times before stopping — a limit now known as the Hayflick limit. For decades senescence was regarded as a laboratory curiosity, or at best a defence against cancer, since a cell that cannot divide cannot become a tumour. Its darker side emerged later, when researchers found senescent cells accumulating in aged tissues and damaging the tissue around them.

Experiments in mice have been striking. When senescent cells were removed from middle-aged animals, either genetically or with compounds that kill them, the animals showed improved physical function, less inflammation and, in some studies, a modest extension of lifespan. Drugs that selectively target these cells are known as senolytics, and the first of them have entered early-stage human trials.

These trials are small, and their results so far are mixed. Some have reported improvements in walking speed or in markers of inflammation in patients with particular diseases; others have found little. It is far too early to say whether senolytic drugs will become a treatment for ordinary ageing, and the long-term risks of clearing cells that may have protective functions are unknown.

Broader interventions have been harder to evaluate. Restricting calories without malnutrition extends lifespan in yeast, worms, fruit flies and mice, and has become the standard comparison for any proposed anti-ageing treatment. The picture in longer-lived animals is less clear: two careful studies of rhesus monkeys, begun in the same decade, reached apparently different conclusions about whether calorie restriction lengthened life. No controlled trial has shown that calorie restriction extends human life, though short-term studies report improvements in blood pressure and in the control of glucose.

A different line of research concerns the proteins a cell must keep in good order. Throughout life, proteins are damaged by oxidation and by heat, and misfolded proteins can aggregate into clumps that are toxic. Cells defend themselves with a system called proteostasis: chaperone proteins help other proteins fold correctly, and two degradation pathways, the proteasome and autophagy, destroy those beyond repair. Autophagy, in which the cell digests parts of itself, declines with age, and experiments that boost it in animals — by fasting, for example, or by genetic manipulation — tend to improve health measures. Whether these interventions work in the same way in people is not established.

Behind all these mechanisms lies a puzzle about what ageing actually is. One influential framework, proposed by the evolutionary biologist Peter Medawar in the 1950s, holds that natural selection weakens with age: a gene that causes harm only after an animal has reproduced is barely affected by selection, so mutations with late effects accumulate. A related idea is that resources are diverted from repair to reproduction early in life, leaving the body with a limited maintenance budget. On this view, ageing is not a programme but the residue of evolutionary compromise, which helps explain why no single intervention is likely to switch it off.

The practical implications are easily overstated. No drug has been shown to extend healthy human life, and the supplements sold for that purpose are largely unsupported by trials. What the research has produced is a much more detailed picture of how tissues deteriorate, and with it a growing body of evidence that some of the damage can be slowed. Whether that will translate into treatments for the diseases of old age, rather than for ageing itself, remains the more realistic hope.

Every road user has an interest in the competence of other drivers, and every society must decide how that competence is to be checked. Young drivers are tested before they are let loose on the road, and afterwards they are trusted. Older drivers are trusted until something goes wrong. The question of whether this arrangement should change — whether, that is, drivers past a certain age should be required to demonstrate their fitness periodically — raises issues of evidence and of fairness that are rarely kept apart in public argument.

The case for testing rests on a fact that is not in dispute: sensory and cognitive abilities decline with age, on average. Visual acuity, the ability to see in low light, the speed of processing information, the capacity to divide attention between several tasks — all of these diminish, if unevenly, in later life. Most countries already require holders of commercial licences to undergo regular medical checks, and few people object. Since driving is a complex activity involving rapid decisions and the risk of killing other people, the argument runs, it is arbitrary to exempt the private motorist.

Traffic statistics, however, complicate the picture. In many high-income countries the rate of crashes per vehicle-mile rises sharply for drivers under twenty-five, falls steadily through middle age, and stays comparatively low into the seventies. Only among the very old does it climb again, and even then the increase is modest compared with the risks associated with youth. Older drivers also tend to drive less, and to avoid night driving, motorways and bad weather, which reduces their exposure. On some measures, a driver in the seventies is safer than a driver in the twenties.

The more interesting question is why. Part of the answer is experience. Older drivers have encountered more situations, and they compensate, often unconsciously, for failing abilities by slowing down, increasing the gap to the car in front, and choosing easier routes. The compensation may have limits, and it may conceal a problem from the driver as well as from others. But it suggests that age alone is a crude instrument.

Against this, a series of studies has found that cognitively impaired drivers pose a risk that neither experience nor self-restraint reliably offsets. Dementia affects judgement, spatial awareness and reaction times, and its early stages are easily overlooked, by the sufferer above all. Dr Joan Langford, a geriatrician who has assessed hundreds of drivers, argues that the real difficulty is not elderly drivers in general but the minority with undiagnosed impairment, who cannot assess themselves and whose families may be reluctant to intervene. On her account, a universal age-based test is a blunt way of finding them, since it subjects thousands of capable drivers to checks in order to reach a few.

One national road-safety campaign group takes a different view of the same evidence. Its position is that periodic medical checks from the age of seventy are a reasonable price for the risk involved, that they do not stigmatise anyone, and that the very small number of lives saved would justify the inconvenience. Its spokespeople point out that a test is not a ban: the great majority of older drivers would pass easily and go on driving, reassured.

At the other end of the argument, the drivers' associations and, more surprisingly, some road-safety researchers contend that mandatory testing makes roads less safe in aggregate. Dr Martin Okonkwo, who models driver behaviour, maintains that the threat of losing a licence leads many older people to give up driving early, and that a driver who stops is not merely removed from the roads: the person is now walking, cycling or being driven, and there is evidence that former drivers, especially in rural areas, suffer isolation, reduced activity and worse health. He questions whether a policy that displaces a small driving risk into a larger well-being risk has been thought through.

There is also a practical objection. Any test of fitness must be accurate, and the tools available are blunt. A crude eye test or a short questionnaire identifies some dangerous drivers and misses others; sophisticated cognitive assessment is expensive, and its ability to predict real-world crashes is modest. The United Kingdom has long relied on drivers to declare their own medical conditions from the age of seventy, with the licence renewed every three years, and on the police and doctors to report concerns. Whether this voluntary system works well is genuinely uncertain, and comparisons between countries are confounded by differences in road design, speed limits and public transport.

What position should be taken? I would not abolish renewal checks, but I am unpersuaded by proposals for a compulsory test that all drivers past a certain birthday must pass to keep their licences. The strongest option seems to me to be a targeted one: require medical assessment only where there is a reason for it — a diagnosis, an incident, a report from a doctor or family member — and make those assessments thorough when they happen. Coupled with better public transport and support for people who stop driving, such a policy would address the actual danger identified in the research rather than a birthday. The argument that a universal test saves lives is not supported by evidence strong enough to justify treating millions of competent older people as a problem to be processed.