Cardio-metabolic changes after COVID infection
A huge UK study tracking nearly a million patients has just
reported some startling results. The special type of study, a matched cohort
study, was designed to see how COVID affected people after infection with the virus.
Researchers from King’s College London suggest in the BMJ that anyone infected
with COVID should consider steps to reduce diabetes risks in the months after
infection.
COVID has been widely associated with the onset of new cardiovascular
disease (CVD) and diabetes mellitus (DM). However, it had not been known whether
the virus had long-term impacts on the conditions.
Although acute COVID-19 has a suspected association with
cardiovascular complications and problems with blood glucose disorders, the
evidence was not clear. There are concerns that patients recovering from COVID
may be at increased risk of CVD and DM, but definitive proof was not available.
Now a huge study tracking patients across the UK for over a
year has shown that COVID infection does indeed significantly increase the risk
of serious cardiovascular problems and diabetes.
The study found:
- An eleven-fold increase in the risk of having a pulmonary
embolism after COVID infection
- Diabetes diagnosis levels were 81% higher following COVID infection
- A number of other serious cardiovascular risks were hugely elevated after infection
Could the study be trusted?
The design of any study or clinical trial is hugely
important. Results from studies with small numbers of participants can be
difficult to rely upon. Sometimes studies can be open to accusations of bias,
or selective reporting of data, which is why we always pay close attention to
the design of any study, the data assessed and especially who funded the study.
The data assessed was made available via the Clinical
Practice Research Datalink under license from the UK Medicines and Healthcare
Products Regulatory Agency (MHRA).
Firstly, the cohort assessed is huge, with 428,650 COVID-19
patients who were matched with 428,650 control patients. The patients’ health records
were tracked and followed up to January 2022. The large study size means statistical
anomalies are less likely to occur – the data comes from a large enough set for
results to be reliable.
The authors declared that they were supported by NIHR
Biomedical Research Centre at Guy’s and St Thomas’ NHS Foundation Trust, King’s
College London and the British Heart Foundation. All are reputable
bodies. It would be difficult for them to be accused of having a commercial
interest in the outcomes of the study.
What did the study find?
The study looked for new cases of cardiovascular disease and
diabetes up to 12 months after infection with COVID-19. The results were
compared with patients who had not had COVID-19.
The authors found:
- New diagnosis of diabetes mellitus increased by 81% in those
who had COVID-19 and remained elevated up to three months after infection
- New cardiovascular disease diagnoses were associated as
being six times higher following COVID infection
- Cases of pulmonary embolism were associated as being 11
times higher following COVID infection
- New cases of atrial arrythmias (where the heart beats in the
wrong rhythm) had a 6-fold increase and venous thromboses (blood clots, e.g.
deep vein thrombosis) had a five-fold increase over the group who were not
infected with COVID
- CVD diagnosis rates declined up to three months after infection and returned to normal levels between three months and a year after infection
What do the findings mean?
The implication is that acute COVID-19 is associated with a
significantly higher risk of developing serious cardiac problems and diabetes
mellitus for up to three months after being infected.
The study did show that risk levels seem to return to normal
population levels fairly soon after infection. The risk of a new diagnosis of
diabetes mellitus remains higher than usual for at least three months after
infection.
The study did not show that people who did not already have
CVD or DM who contract COVID have a longer-term increase in the risk of
developing the conditions.
The limits of the study
Although it was large and seemingly well structured, the
study included patients with both confirmed and suspected COVID. However, the
authors ran a sensitivity analysis to see if only relying upon PCR confirmed infections
and found that the conclusions were not altered.
It was possible that the control group might have been
contaminated with undiagnosed infections, especially from those were had been
asymptomatic. This risk was particularly high in the early stages of the
pandemic, when mass testing was not available.
The UK ONS weekly surveys from October 2020 to October 2021
showed that fewer than 2% of the population was infected with COVID-19 in any
given week. That means the probability of a participant in the control group
having undiagnosed COVID was less than 0.02, which should have had limited
effect on the results.
Sadly, many values in health records are commonly missing,
which made inputting data in directly comparable ways more difficult.
The data also showed that those with COVID-19 had more
consultations with doctors. Whilst this is commensurate with having been
unwell, it is possible the increased medical contact could have been associated
with more opportunities for diabetes to be diagnosed.
The authors also noted that “Patients diagnosed with
COVID-19 were generally less healthy than controls and this might, in part,
account for differences in cardiometabolic outcomes.”
It’s also important to note that several variants were
present at different times when the data was captured, which might be associated
with very different affects on the body and clinical outcomes.
It is also possible that the authors may have drawn the wrong conclusions from the data sets. However, the report has been peer-reviewed, so this risk is hopefully reduced in practice.
Conclusions
The report is large and well-structured. It is from reputable
sources. Whilst it is perhaps a little surprising it has not been referenced more
in mainstream media, it will influence clinical practice.
It is suggested that anyone recovering from COVID should
consider taking steps to reduce individual diabetes risk, including eating a healthy
diet and participating in regular exercise.
The full report from the study can be read online.
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