Danish researchers have found a very surprising association between children’s height at 7 years old and the risk of developing systemic lupus erythematosus in adulthood. The researchers also found that high body mass index in childhood increases the risk of developing lupus.
A Danish study of health data on more than 345,000 children shows an unexpected association between height, body mass index (BMI) and the risk of developing the autoimmune disease systemic lupus erythematosus in adulthood.
A 7-year-old girl who is 5.3 centimetres taller than another 7-year-old girl has an 11% higher risk of developing lupus.
Further, a girl who weighs 2.3 kilograms more than another girl of the same height has a 13% higher risk of developing lupus.
“We were very surprised that height during childhood is associated with an increased risk of developing lupus. Our study indicates that lupus may begin in childhood and that this is where we should investigate its origins and the various risk factors,” says co-author Jennifer L. Baker, researcher, Center for Clinical Research and Prevention, Bispebjerg and Frederiksberg Hospital, Copenhagen.
The new study has been published in Seminars in Arthritis and Rheumatism.
Lupus more common among women
Systemic lupus erythematosus is a chronic autoimmune disease that causes inflammation of the connective tissue.
Lupus results from the body’s immune system making a mistake and attacking the body’s own cells. In the process, antibodies are formed that lead to the inflammation.
The underlying cause of lupus is still unknown, but most doctors and researchers agree that genetic and environmental factors play a role in its development.
Lupus is most common among women 20–30 years old and can be treated with anti-inflammatory medicine.
“We know that obesity in adulthood is associated with an increased risk of lupus. Few studies, however, have investigated the association with childhood overweight or birthweight,” explains Jennifer L. Baker.
A very rare disease
The researchers examined records from the Copenhagen School Health Records Register for 346,627 children who were born in Denmark between 1930 and 1996 and then attended school in Copenhagen.
The researchers noted the children’s height and weight and the birthweight of those born after 1936, when doctors routinely began to record this information.
Then the researchers linked these data with data from the Danish National Patient Registry to determine which children developed lupus later in life.
During the study period, 435 people developed lupus, of whom 366 were women.
This suggests that the disease is relatively rare.
“By comparison, 30,000 to 40,000 of the people included in the study would be expected to develop various types of heart disease during the study period,” says Jennifer L. Baker.
No association between birthweight and lupus
The study showed that birthweight is not associated with the risk of developing lupus.
In contrast, the risk of developing lupus differed depending on childhood BMI.
A higher BMI was associated with increased risk.
More precisely, the researchers found that a 7-year-old girl who weighs 2.3 kg more than another 7-year-old girl of the same height has a 13% higher risk of developing lupus.
“This difference is not huge, but it is statistically significant and provides insight into the risk factors associated with developing lupus. Further, it is surprising that childhood BMI, but not birthweight, affects the risk,” explains Jennifer L. Baker.
Fat can lead to inflammation and then to autoimmune disease
Jennifer L. Baker states that the link between adipose tissue and inflammation may explain the association between BMI and the risk of developing lupus.
The more fat in the body, the higher the degree of inflammation, and similar to other autoimmune diseases, this may contribute to developing lupus.
“The body’s levels of estrogen may be another possible cause of developing lupus, and this may explain why more women than men develop lupus,” says Jennifer L. Baker.
Taller children at greater risk
To their great surprise, the researchers also found an association between height during childhood and the risk of developing lupus: the taller the child, the higher the risk of developing lupus in adulthood.
Jennifer L. Baker points to the example of a 7-year-old girl who is 5.3 centimetres taller than another 7-year-old girl having an 11% higher risk of developing lupus.
“We cannot yet provide a good explanation, but genetics is probably one reason. The result is also interesting because no one has yet investigated whether height is associated with lupus in adulthood,” explains Jennifer L. Baker.
Jennifer L. Baker says she hopes that other researchers will pick up these findings and delve deeper and further study the associations between height and weight during childhood and the risk of developing lupus in adulthood.
“We are trying to understand the origin of lupus. We have now identified that something early in life affects the development of lupus. The next step will be to examine what mechanisms may underlie this relationship, such as genetic and environmental factors,” says Jennifer L. Baker.
“Early life body size, growth and risks of systemic lupus erythematosus – a large Danish observational cohort study” has been published in Seminars in Arthritis and Rheumatism. In 2018, the Novo Nordisk Foundation awarded a grant to Jennifer L. Baker for the project Early Life Body Size, Growth and Pubertal Timing and Risks of Systemic Lupus Erythematosus.