© Murdo MacLeod/The GuardianThe research is the biggest study of the suspension of NHS care during the coronavirus pandemic.
Seven out of 10 diabetics, 65% of those with high blood pressure and 64% of people suffering from breathing problems have had care cancelled by the NHS across the UK during the pandemic.
Even a majority of cancer patients - 53% - have been left unable to access treatment in the normal way, the biggest study of the suspension of NHS care during the pandemic has found.
The findings, which the authors have shared with the Guardian, demonstrate that large numbers of people with health problems could not have surgery, diagnostic tests or outpatient appointments.
A majority of people with cardiovascular illnesses (60%) and brain problems (66%) had their care cancelled, as did 68% of people with arthritis and 78% of very overweight people, who are at greater risk of health problems.
Overall barely one in five (21%) of those who regularly receive NHS help for a long-term health condition were able to have a planned treatment in April, the study found. Cancer patients (34%) were the most likely to receive care as normal, but only 10% of very overweight people did so.
The conclusions have come from academics at Essex University led by Prof Michaela Benzeval, the director of its Understanding Society study at the Institute for Social and Economic Research, which undertakes longitudinal research into life in the UK and is funded by the Economic and Social Research Council.
Their stark findings, based on the experience of 3,414 people with health problems, have prompted experts to warn that patients' inability to access care in recent months could damage their health, increase the already large number of people on NHS waiting lists and even cost lives.
Rachel Power, the chief executive of the Patients Association, said: "While the radical changes the NHS made to its services were impressive as an organisational feat, it should not congratulate itself too quickly. The consequences for patients of so much treatment being curtailed have not yet been identified.
"This emerging research suggests they might prove to be very serious indeed."
Prof Martin Marshall, the chair of the Royal College of GPs, stressed that the NHS's "difficult decision" to cancel so much planned care during the pandemic was intended to stop patients getting coronavirus by coming into hospital for care and to free up staff to concentrate on the disease. But it resulted in a backlog of patients whose operation or assessment now needed to happen as soon as possible, he added.
Marshall said: "Although these health interventions might not have been deemed critical, they will have been necessary for our patients, or else they would not have been recommended. In some cases, the longer patients have to wait, the more likely it is conditions will deteriorate."
The research is the first to quantify how many patients decided not to proceed with a scheduled test, operation or outpatient consultation. NHS leaders and senior doctors have pointed out that many patients were too scared to come into hospital.
One in 10 people cancelled their own care, the research found. People with respiratory problems (12%), cardiovascular conditions (12%) and diabetes (11%) were the most likely to do so. But only 7% of cancer patients opted not to proceed.
More positively, the study also found that, despite the suspension of so much hospital-based care, 98% of people were still able to obtain prescription medications and 75% could access GP services or see a pharmacist. "It's encouraging that a high proportion of people have been able to access care in the community," said Marshall.
Jennifer Dixon, the chief executive of the Health Foundation, which co-funded the research along with the ESRC, voiced unease about its findings.
She said: "These findings show the serious impact Covid-19 has had on the delivery of services for people with long-term conditions like cancer, diabetes and cardio-vascular disease. That 63% of people with serious long-term conditions had their planned treatment cancelled suggests we may be storing up greater health problems for the future.
"While measures were put in place to protect and support vulnerable people, it's evident that many people's needs may have gone unmet during the lockdown, meaning their conditions may have worsened when they should have been receiving care."
Benzeval said the widespread lack of treatment was "obviously worrying for the individuals concerned, and may impact on their long-term outcomes".
A spokesperson for the NHS in England said: "Data for health service usage show a strong rebound in patients coming forward for check ups and treatment. The ONS report today has not found evidence of significantly increased cancer mortality, with Covid-protected cancers hubs in place and almost 30,000 people starting cancer treatment in March. For other conditions such as heart problems, the number of people coming to A&E is now back to the levels we would normally expect."
Comment: The lockdown was sold as an unprecedented measure intended to protect the elderly and vulnerable but instead led to the abject neglect of those it claimed to be protecting. As we can see in the Office of National Statistics Excess Deaths graph below, the first spike, likely due to the coronavirus, began in January, the second and much larger spike occurred at the beginning of the lockdown, 27th March.
Coronavirus didn't cause the majority of excess deaths in the UK, the lockdown did.