Reinfections with SARS-CoV-2, the virus behind Covid-19, is less likely to cause long Covid -- a condition that affects at least 65 million people worldwide, according to a study.

Long Covid affects people after an infection caused by the SARS-CoV-2 virus. The condition is not properly defined yet presents more than 200 symptoms. Long Covid risk and severity is known to compromise self-rated health, physical capacity, and cognitive function.

The preprint study, not peer-reviewed yet, showed that the risk of Long Covid was 6 per cent after reinfections from Covid virus compared to 15 per cent after the initial infection.

Fatigue, shortness of breath, neurocognitive symptoms, post-exertional malaise, and smell or taste disturbances were the most reported common symptoms among people with long Covid.

"Severe symptoms were reported 5 to 22 times more often by long Covid cases than by Covid controls, except for fever, cough, insomnia, anxiety, and depression (2.7 to 4.5 times)," said the Laval University in Quebec, Canada.

The study is based on 22,496 online survey participants and 3,978 telephone survey participants.

Early-life exposure to small particle air pollution and outdoor artificial light at night could increase the risk of paediatric thyroid cancer, a new study led by researchers at Yale University in the US has suggested.

The team found a “significant association” between exposure to ambient fine particulate matter air pollution (PM2.5) and outdoor artificial light at night (O-ALAN) and increased risk of papillary thyroid cancer in children and young adults up to 19 years old, according to the study published in Environmental Health Perspectives.

The exposures occurred during the perinatal stage of life, typically defined as the time from when pregnancy occurs up to a year after birth.

Western diet, often high in salt, sugar and fat, has the potential to raise the risk of cancer in the lungs, finds a study.

Previous research has shown the link between poor diet and cancers of organs like the liver and pancreas; thus the long-term impact of diet has been well studied.

"Lung cancer has not traditionally been thought of as a dietary-related disease," said Ramon Sun, Associate Professor and director of the University of Florida’s Center for Advanced Spatial Biomolecule Research.

"Diseases like pancreatic cancer or liver cancer, yes. However, when it comes to lung cancer, the idea that diet could play a role is rarely discussed," Sun added.

For the study, published in the journal Nature Metabolism, the team focussed on glycogen accumulation -- a storage molecule, made up of glucose, or a simple sugar. It has been found to accumulate at high levels across a variety of cancers and other diseases.