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Is Having A Younger Sibling A Factor That Can Prevent Diabetes in Later Life?

Apr 23, 2016

Study finds birth of younger sibling between 9 and 54 months decreases obesity odds for older sibling.

Children who experienced the birth of a younger sibling between the age of 9 and 54 months have a lower chance of being obese as compared to the singletons.


Obesity as one of the risk factors for developing diabetes is a well-established fact.  Healthcare providers stress the importance of balanced diet and exercise to help prevent this chronic disease.  A just published study by Rana Mosli and colleagues indicates that having a younger sibling could be a significant aspect of maintaining a healthy body mass index (BMI) in kids.

The study looked at 697 participants who lived in 10 different sites in the United States between 1991 and 1998. Participants’ body mass index z-score (BMIz) was calculated at 15 months, 24 months, 36 months, 54 months of age, and in first grade when they were six years old. They found that children with at least one younger sibling who was born when they were between 24 to 36 months, or between 36 to 54 months old, compared with children who did not experience the birth of a sibling by first grade, had a lower subsequent BMIz trajectory and a significantly lower BMIz at six years of age (0.27 vs 0.51, P value = 0.04 and 0.26 vs 0.51, P value = 0.03, respectively).  When looking at the children who did not have a sibling at six years of age, their odds of being obese were 2.94 times higher than a group of children who had a sibling when they were between 36 to 54 months old (P value = 0.046). Interestingly, when children had their sibling born when they were between 9 and 24 months old, their BMIz was influenced the least as compared to the group of children for whom that event happened later in life.  The effect of having a sibling on their BMIz was not significant as compared to the group of singletons (0.47 vs 0.51, P value = 0.53).

Authors of the study tried to find the reasons behind these findings. They hypothesized that it could be that when the difference of age between the siblings is more than 2 years, the older sibling takes a role of a leader and caretaker and initiates activities for a younger playmate. It could also be because of change in eating habits after the birth of a younger sibling. As a new family member is born, parents do not have time to be restrictive towards eating habits of the older child and as earlier studies found, restrictive eating habits are associated with a higher BMI of a child later in life. Between 0-3 years of age is a crucial time for humans to create eating habits that affect their lifelong relationship with food.

This study had a few limitations that are worth mentioning. It was conducted during the 1990s. Much about the interactions between the siblings might have changed as compared to today. Also, researchers created only two categories of children: with or without a younger sibling. If participants had multiple younger siblings, it has not been differentiated in the study. We also do not know the effect on BMIz if a child has an older sibling, or how home and school environment and both parents’ education level throughout the time span of the study, child’s physical status, or diet patterns affected the results of the study. There certainly are more questions that could be answered and further studies need to be performed in order to fully understand the phenomenon of how having siblings affects children’s weight and health.

Practice Pearls:

  • Having at least one younger sibling born between 24-54 months of age can help a child have a lower BMIz as compared to singletons.
  • If children have no younger siblings, it is recommended for them to get involved in activities with their peers or younger friends so they can experience partial benefits of interactions that resemble younger siblings’ relations.
  • All healthcare providers should still recommend balanced diet, physical activity, and limited screen time to children of all ages to in order to help them to thrive.

Researched and prepared by Renata Kulawik Doctor of Pharmacy Candidate LECOM College of Pharmacy, reviewed by Dave Joffe, BSPharm, CDE


Mosli, Rana H., et al. “Effect of Sibling Birth on BMI Trajectory in the First 6 Years of Life.” Pediatrics (2016): peds-2015.  Isaacs, A.N., and A. Vincent. “Antihypertensive therapy for the prevention of nephropathy in diabetic hypertensive patients.” Journal of clinical pharmacy and therapeutics (2016).