A man who experienced the onset of puberty earlier than usual is at a higher risk of developing type 2 diabetes as an adult, compared to boys who have later puberty. This trend does not depend on childhood weight. The study, published in the journal Diabetologia in March 2020, may help establish guidelines for prevention and testing for diabetes in men.
Early puberty and risk for type 2 diabetes in men. Image Credit: Urbans / Shutterstock
The researchers looked at over 30 000 Swedish males born between 1945 and 1961 who had BMI measurements at the age of 8 years and 20 years, as part of the population-based BMI Epidemiology Study Gothenburg.
They used peak height velocity, the time when boys experience the fastest growth in height during puberty. It occurs about two years following the onset of puberty. Earlier research by the same authors showed that a higher BMI in prepubertal boys is linked to an earlier age at puberty.
Using this criterion, they established the age at which the boys had their pubertal growth spurt. They classified the boys into different categories: 9.3 to 13.4 years, 13.4 to 14.8 years, and 14.8 to 17.9 years. The average age of puberty was 14 years.
The height and weight data during childhood and adolescence were then followed up from national registers up to the end of 2016, or until the development of type 2 diabetes, or until they emigrated or died. The average period of follow up was about 31 years.
The researchers found that about 1850 men developed T2DM over this period. The age point of 57.2 years was the median point of diabetes development in the study and was therefore taken as the factor to differentiate early and late diabetes mellitus. The number of study participants who developed early and late T2DM were roughly equal.
They then looked for the development of type 2 diabetes mellitus (T2DM) at age 57 or before, which is called early type 2 diabetes. For each year earlier that the growth spurt occurred, the risk of T2DM went up by 28%. They found that the boys who had their growth spurt at the youngest age had a twofold risk of early T2DM compared to those who had the latest growth spurt.
Their risk of late T2DM, which sets in after 57 years, was increased by 27%, or 13% per advanced year of puberty. They adjusted the data to account for differences in the body mass index during childhood as well.
On the other hand, when the BMI at 20 years of age, that is, after puberty, was factored into the analyses, the link between early puberty and early T2DM became weaker though still significant, at a 16% increased risk for each year earlier than puberty occurred. Also, the association with late T2DM became insignificant.
Early puberty was linked to a 25% increased risk of insulin-dependent T2DM per year of earlier puberty.
Late puberty, which occurred in 20% of the sample, was linked to a 30% reduction in the risk of early diabetes compared to those who entered puberty at the usual age.
The researchers also took into account several other factors, including birth year, birth country, birth weight, and level of education. It is already well known that a high adult BMI indicates a higher risk for T2DM also, earlier research shows that boys with a high BMI in childhood or during puberty, have a greater risk.
Puberty studies in girls have suggested that earlier onset of puberty in girls, as defined by the beginning of menstruation, is associated with a higher risk of diabetes. However, similar studies in boys are more difficult because the markers of pubarche in boys are less distinct.
The new study was aimed at identifying a link between the time of puberty onset and diabetes risk in men, independent of the effect of BMI, after using an objective parameter to pinpoint the timing of puberty onset.
Researcher Jenny Kindblom says, “Our findings suggest that early puberty could be a novel independent risk factor for type 2 diabetes in men. Given the higher risk among boys who start puberty before the average age of 14 years, we estimate that 15% fewer men who were diagnosed during the study would have developed type 2 diabetes had they not started puberty early.”
The underlying mechanisms of this association may be the build-up of excess fat in the abdominal area associated with earlier puberty. Visceral fat accumulation leads to high blood pressure, diabetes, and high-fat levels, which are all risk factors for cardiac and metabolic disease.
In addition, the researchers say, “These findings strengthen the concept that early puberty is part of an adverse trajectory during childhood and adolescence, and that a high BMI both before and after puberty contributes.” She thinks that monitoring height and weight development during both childhood and adolescence could help to pick out individuals who are at higher risk for T2DM.
The observational nature of the study makes it difficult to prove that the cause of the increased risk is early puberty. Moreover, the study did not include information about BMI after 20 years of life, family history of diabetes, or a personal history of smoking. These factors, which are independent risk factors for diabetes, were not compensated for in the analysis. The overwhelmingly white participation in the study also limits its generalizability to other ethnic groups with a high risk of T2DM.
Ohlsson, C., Bygdell, M., Nethander, M. et al. Early puberty and risk for type 2 diabetes in men. Diabetologia (2020). https://doi.org/10.1007/s00125-020-05121-8