Coronary heart disease and cancer rates among people with learning disabilities are nearly a third lower than the general population, says new research.
But experts say this may be because they are difficult to diagnose, as people with a learning disability are less capable of articulating their conditions, and so medical staff may be missing some indications when diagnosing.
The study also found people with a learning disability are disproportionately more likely to suffer from serious mental health issues like schizophrenia and mood disorders and chronic conditions such as epilepsy, diabetes, an underactive thyroid and kidney disease.
It analysed electronic GP records of 14,751 adults with a learning disability, which included a range of conditions such as Down's syndrome and autism, compared to 86,221 patients of similar age and sex in the general population.
Dr Iain Carey, of St George's, University of London, said the findings on the incidences of chronic disease in people with a learning disability raise concerns over inadequate identification of some conditions.
"The low prevalence of coronary heart disease is surprising given the high prevalence of risk factors including diabetes, obesity, an underactive thyroid, chronic kidney disease and stroke," he said.
"Similarly, the lower prevalence of cancer needs further exploration because it may indicate late diagnosis or poorer survival. A potential alternative explanation for these findings is there are lower rates of smoking and alcohol use among adults with a learning disability, but it is hard to say without further evidence."
The research also found that patients with learning disability were less likely to have longer doctor consultations and had lower continuity of care with the same doctor.
Dr Carey said people with a learning disability needed access to high-quality chronic disease management in primary care.
"The high prevalence of epilepsy and severe mental health problems in people with a learning disability requires effective access to specialist advice," he said.
"Continuity of care and longer appointment times are important potential improvements in primary care."
The research was published in the British Journal of General Practice.