Doctors' failure to recognise that her mother was suffering from CJD alerted Judith Okely to the medical profession's inherent ageism.

The crisis over mad cow disease has shown how scientific research can be manipulated politically. It also shows how scientific and medical knowledge are socially constructed and ageist. Recently, a government adviser, Roy Anderson, conceded that more attention should be paid to the possible death of the aged from variant Creutzfeldt-Jakob disease. As a social anthropologist who has conducted research among the aged in the United Kingdom and France, I have been arguing for such research since 1992 and, indeed, submitted an article to the government's bovine spongiform encephalopathy inquiry.

In 1992, I telephoned the Edinburgh CJD unit to suggest that CJD among the aged might have been rendered invisible. This idea was dismissed immediately by a researcher at the unit, who cited as evidence a study in another European country, in the 1950s or 1960s, that had analysed the brain tissue of all the aged residents of institutions and found that the percentage of those with CJD was no higher than average. The social scientist in me remonstrated that the research was several decades old and was conducted outside the UK before the BSE crisis. The researcher fell silent.

Apparently, years later, the unit has received a grant to investigate the reservations I had brought up. Will social science be credited with an earlier scepticism about the alleged age neutrality of scientific research?

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My call to Edinburgh had been triggered by shocking news that had brought the subject much closer to home. I had been informed, months after the event, that my mother, Bridget, had not died of Alzheimer's, as asserted by numerous medical experts, but of CJD. Until then, I had never heard of it. Medical encyclopedias stated that the illness affected 1 person in 5 million. In one swoop, Bridget's chance diagnosis had doubled the record for the equivalent population of Scotland. It was revealed only because my sister and I had shown scepticism about the label "dementia" and had, after persistent phone calls, found an institution, Bristol University, that accepted her brain tissue for research and provided a diagnosis for free. A thorough postmortem examination for a 72-year-old woman was never on offer and experts have recognised that the brain tissue of elderly people is rarely examined at post mortems.

Eight years on, a 74-year-old man has been diagnosed as dying from vCJD. This may not be the first case, however, because illness among the over 60s is often naturalised. My mother, with classical CJD, had, nonetheless, shown all the symptoms associated with vCJD victims, yet in her case, these were systematically overlooked.

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In 1996, the government and the media responded dramatically to a CJD variant, not only because it was new, but because it had been located among "young persons". In a society that privileges youth, the aged are, by contrast, perceived as unproductive and more disposable (the Harold Shipman case is another good example). Medical attention and scientific curiosity are thus infected.

Bridget was a university lecturer who led an active and intellectually rewarding existence for more than five years after official retirement. Many of us would presume that a general practitioner would be capable of reasonably sophisticated assessment of the mental state of such an intellectual.

As a social anthropologist, I found the fundamental research method of participant observation poignantly relevant in understanding the changes in Bridget. The same "grounded knowledge" was to be found among her neighbours and friends, who noted her increasingly erratic behaviour. Similar participatory knowledge could be found among the nurses and health visitors who did the caring. Yet for months Bridget's GP assured us there was nothing wrong. She was just "rather emotional". Alien tingling in her legs was "inevitable" at her age.

The doctor's proof of her normality was a test devised in the name of objective generalisability. The formulaic questions and answers included ones about the informant's age, number of children and the prime minister. Bridget regularly came out with top marks. If doctors were not in thrall to such standardisation, they would see that information was there to be gleaned. My mother had developed brilliant strategies. She declared that, as a retired person, the day of the week was irrelevant. When asked about the prime minister, she replied: "Do you want me to talk about Lloyd George, Disraeli, Churchill, Macmillan, Heath, Wilson or the bitch?" But could she still remember the year Thatcher was elected? This was once engraved on her memory as the start of the destruction of the welfare state, which she had worked for and lectured about for decades.

A friend's father who had been editor at a university press passed the same test despite worrying mental deterioration. It would have been better if he had been asked to translate, as was his wont, the day's Times newspaper into Greek. The aged are treated as a homogenised lump. Significant differences in biography are made irrelevant. Most become mere "pensioners" in the dominant medical and political ideology.

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In the summer of 1993, like other relatives of those who had died of CJD, I was interviewed by the Edinburgh CJD unit, which had received her documentation. I noticed a UK map with pins for each CJD death. There were no pins in Cornwall where Bridget had lived for 15 years, before moving to a Wiltshire nursing home for her final weeks. I was informed that the pins marked the place of death, not residence. The map was misleading, while giving the illusion of factual mastery.

From December 1992, I had accumulated mounting evidence of the possible links between BSE and CJD from occasional publications, the media and comments by the microbiologist Richard Lacey. One documentary depicted a relative who claimed that the CJD unit interviewer warned her that any public link made between BSE and CJD would affect the beef industry. The head of the unit denied to me that this had been said. When I asked him about possible BSE/CJD links, I was told categorically there were none.

Fortunately, I had been a vegetarian for years. But the unit's pre-1996 denial of any risk in beef is disturbing, given the risk that some individuals may be more genetically vulnerable to CJD. Was this denial, I then wondered, in the name of controlled science, protection of the meat industry, or the safeguarding of government funding to the university? In our youth-obsessed society, the exact cause of death among the aged is regarded as relatively unimportant. Six months before my mother's death, a consultant finally diagnosed "dementia" and sanctioned my mother's bladder operation. In fact, the bladder problems might have been CJD-related. More seriously, undiagnosed CJD sufferers can bequeath contamination of surgical instruments to others.

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The operation exacerbated Bridget's condition. I looked after her through the summer. Her GP eventually conceded the extremity of her condition, although he still labelled it dementia. After a repeat of the little test, what most alarmed the authorities was Bridget's claim to have 2.5 children. I smiled at the sociologist surviving within her.

We placed Bridget in a wonderful nursing home. Yet until the end, the consultant and doctors failed to recognise anything beyond the catch-all Alzheimer's. The staff were fascinated by her photo albums and mementos of global travels. Bridget was envisaged as a person with a biography: once young, as a social worker and lecturer. Now, she could only stroke her daily newspaper.

Our roles were reversed. She gave birth to me during the siege of Malta and watched the bombing of Valetta harbour from her birthing bed. My christening robe had been embroidered by Maltese nuns. Bridget located the last photographer in Malta and posed with me in front of a bomb-damaged wall.

To give nuanced attention to their illnesses and to repay the aged for their past caring is the least we can do.

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Judith Okely is professor of social anthropology at the University of Hull and author of "Love, care and diagnosis" in Extending the Boundaries of Care , edited by Tamara Kohn and Rosemary McKechnie (Berg), ?14.99.