Firstborns may be at a higher risk for heart disease and diabetes compared to middle children and later-born ones, a recent study suggests.
Researchers from the University of Auckland in New Zealand researchers looked at 50 overweight men between the age of 40 and 50, and compared their body mass index (BMI) of those who were first born with those who are second born. The researchers also looked at their level of sensitivity to insulin, the hormone that is in charge of regulating blood sugar levels in the body. Results showed that althoug the two groups of men had similar average heights, firstborns were 15 pounds heavier.
Among firstborns, the average BMI was 29, compared with 27.5 for second-born men. Insulin sensitivity in firstborns was 33 percent lower than in second-born men. These findings suggest that birth order could potentially have long-term birth effects. However, larger studies that compare siblings to each other are still need to confirm their findings. Previous studies have shown that birth order may also influence metabolism and body composition in children. It's unclear though how birth order might influence metabolism exactly, but it is possible that differences in placenta blood flow play a part.
The researchers involved in the study stressed and cautioned that their research only involved overweight men, living in urban areas, and said that their findings may not necessarily apply to other groups of people. Their research was published in the journal The Journal of Clinical Endocrinology & Metabolism.
