“Oh, he’s been so brave and good. He’s not made a fuss at all.” That’s what the well-meaning care worker said about my autistic older brother after he broke his nose in an epileptic seizure some years ago. Except that Timothy wasn’t being brave or good – he’s just not able to tell us when something is wrong; he doesn’t have the words for it. Like a third of people on the autistic spectrum, my 58-year-old brother has very limited verbal communication. He can speak, but usually only when prompted, and in learned, short phrases or single words. And like the majority of people with autism, he has unusual sensory responses. We suspect that he doesn’t feel pain in quite the same way we do.

There is a saying that when you’ve met one person with autism, you’ve met one person with autism – it is notoriously hard to generalise about a condition that takes in such a wide spectrum, from the highly intelligent but socially awkward adult to the profoundly learning-disabled child who will need lifelong support. But there are certain health issues that crop up so often that all those with autism, their advocates and medical professionals need to be aware of them.

Many are hypersensitive and react excessively to even the lightest touch and smallest discomfort; others, such as Timothy, are hyposensitive and symptoms of quite major problems go unnoticed. You have to know him well, spot small behavioural changes and explore the reasons for them. Recently, the very conscientious manager of Timothy’s home got in touch because he was agitated and slapping his face. We thought he might be mimicking someone at his day centre, but asked her to take him to his GP and dentist. Sure enough, he had an infected root canal that needed treatment. A course of antibiotics, and he is happy again.

These days, Timothy lives with observant staff who know him well and pick up the subtle signs if something is not right. But, sadly, not everyone on the spectrum has people watching out for them, especially when they are adults and don’t live with their families. Poorly trained and poorly paid careworkers don’t stick around long enough to get to know the people they are supporting intimately, and neglect happens all too often.

There are hardly any long-term studies of people with autism as they age, but US research has estimated that life expectancy is far shorter for them than for their unaffected siblings or cousins – especially if they have learning difficulties as well. On average, people with autism and learning disabilities die between 10 and 20 years prematurely.

Despite campaigns by Mencap and increased awareness, Dr Pauline Heslop, the lead author of a groundbreaking UK study into premature deaths, said: “The unacceptable situation remains that for every one person in the general population who dies from a cause of death amenable to good healthcare, three people with learning disabilities will do so.” Among Timothy’s peers, we know of several who have died too young when cancers have progressed unnoticed, or when their unchecked consumption of water, food or non-food items has led to catastrophic ill health. Meanwhile, epilepsy affects 20-40% of people with autism and is one of the major causes of premature death, along with respiratory, cardiac and dysphagia disorders. While articulate autistic adults can face troubling health problems too, these issues can be a particular cause of concern for people who can’t speak for themselves.

All too often, medical professionals are inexperienced around autistic non-verbal adults and don’t know that their behaviour may be a form of communication. They sometimes dismiss their actions as a quirky autism trait. Jim Blair, a consultant learning disability nurse, campaigns for better treatment of adults and children with learning disabilities in hospitals. Currently, fewer than half of hospitals in the UK have a learning disability nurse on staff. In the past, Blair has worked with doctors who see a non-verbal patient banging their head against a wall and write it off as “habitual autistic behaviour”, rather than investigating whether the patient is in pain and is trying to blot it out by head-banging.

Heslop would like to see learning disability nurse specialists working across GP practices, advising and training medical staff and carers. She believes that good-quality health checks and prevention work – not just box-ticking exercises where forms are filled in then forgotten in a drawer – could lead to far fewer people with autism needing hospital care and dying prematurely.

In recent years, some excellent resources have been created, such as the Books Beyond Words series that explain health problems in pictures. Visual pain scales (smiley to sad faces) and the videos and photo-stories on the Easyhealth site (designed by the learning disability charity Generate) can also help non-verbal communication.

Campaigners such as the National Autistic Society encourage the use of health or hospital “passports”. These are personalised documents that accompany someone with autism who can’t speak for themselves. They give vital personal history, medical information, sensory idiosyncrasies and advice on how the patient might behave if stressed by their surroundings or illness. Many health workers find the passports very useful when faced with a new patient with baffling behaviour and no speech, but there are also reports of the documents being ignored by busy professionals who think they do not have time to read them. There is no statutory obligation to take account of a health passport.

There is a very convincing argument that the main reason autism rates have risen to one in 100 in recent years is because of growing awareness of the diversity of autism, leading to many more diagnoses. But diagnosis is just the beginning – in order for people such as Timothy to have a long, happy life, we need greater awareness not just of autism, but how it can affect overall health.