YOUNGER siblings are 13 per cent more likely to suffer a severe form of arthritis in later life, a study shows.
Having older brothers or sisters heightens the risk of ankylosing spondylitis — a type of chronic inflammatory arthritis, Swedish researchers found.
GettyYounger siblings are 13 per cent more likely to suffer a severe form of arthritis in later life, a study shows[/caption]
Children who had their tonsils removed because of tonsillitis are also 30 per cent more likely to get the condition.
Scientists said younger siblings are exposed to more infections in early life, which could increase their chances of developing it later on.
Dr Matilda Morin, of the Karolinska Institutet, said: “Having older siblings and a history of tonsillectomy were independently associated with development of ankylosing spondylitis.
“This was the case even after adjustment for family shared factors in a sibling comparison analysis.
“The mechanism behind this risk increase cannot be determined from our data but it has been shown that infants with older siblings are more exposed to infections early in life than infants without siblings.”
Ankylosing spondylitis causes inflammation in the spine, joints and tendons, resulting in pain, stiffness, and fatigue.
It affects around 200,000 Brits and there is no cure.
Treatments involve treating symptoms through a combination of exercise, physiotherapy and anti-inflammatory drugs.
While genetic risk is the leading cause of the disease, scientists believe early life factors may also play a role.
The study, published in the journal RMD Open, drew on health and family information in Sweden to compare exposure to various early life risk factors in adults with and without the condition.
Cases had to have had at least one inpatient or outpatient specialist clinic visit with a recorded diagnosis of ankylosing spondylitis between January 2001 and December 2022.
Each case was matched for sex, year of birth, and region of residence with an average of four members of the general public who didn’t have the disease.
Early life risk factors included: mother’s age at delivery, her weight in early pregnancy, and whether she smoked; length of pregnancy; baby’s birthweight; multiple birth; Caesarean section delivery; maternal infections during pregnancy; and season of birth.
Other factors considered were number of siblings; serious childhood infections from birth up to the age of 15; and tonsil or appendix removal before the age of 16.
In all, 6,771 people born from 1973 onwards were diagnosed with ankylosing spondylitis between 2001 and 2022.
Of these, 5,612 were born in Sweden and were selected as the cases.
Several factors were associated with a greater risk, including having just one or more older siblings — but not siblings in general.
Dr Morin said: “Multiple birth, as opposed to singleton birth, was associated with a 23 per cent heightened risk.
“Being born in the summer or autumn months was associated with a significantly lower risk than being born in the winter.”
Having one older sibling increased the risk by 18 per cent, while it was 34 per cent for two or more older siblings, after adjustment for sex, mother’s age, and year of birth.