Boys with a large increase in body mass index (BMI) during puberty are at increased risk of death due to cardiovascular disease (CVD) later in life.
There is no corresponding risk among boys overweight when younger and who have normal weight during adolescence, according to a study from Sahlgrenska Academy.
The study included over 37,600 men born 1945-61, whose height and weight are well documented from both the school health care records and military conscription tests. The change in BMI during puberty was calculated using BMI values at 8 and 20 years of age.
That obesity in adults is a risk factor for cardiovascular disease is well known. The current study, however, is the first to evaluate the contribution of BMI during the two distinct developmental periods; childhood and puberty, for cardiovascular mortality in adult men.
Increased cardiovascular mortality was seen in boys with a large increase in BMI during puberty, while there was no increased risk for those who were overweight prior to puberty but whose BMI normalized during puberty. Thus excessive BMI increase during puberty seems unhealthy.
“In this study, we show that a large increase in BMI during puberty is particularly important, while high BMI at age 8 is not linked to increased risk of cardiovascular death,” says Jenny Kindblom, associate professor at the University of Gothenburg’s Sahlgrenska Academy.
BMI increases during puberty as a part of normal pubertal development. According to the present study, the increased risks occur in the group of boys whose BMI increased by more than 7 BMI units during puberty. Within this group, the risk of death due to cardiovascular disease later in life increases by 22% for every extra BMI unit.
“Our data suggest that BMI should be monitored in schoolchildren extra closely during puberty for the early identification of individuals at high risk of suffering from cardiovascular disease in the future,” says Professor Claes Ohlsson.
Background: Being overweight during childhood and adolescence is associated with increased risk of cardiovascular disease in adulthood, but the relative contribution of prepubertal childhood BMI and BMI change during puberty to adult mortality due to cardiovascular disease is unknown. We assessed the contribution of these two distinct developmental BMI parameters for cardiovascular mortality in adult men.
Methods: As a part of the ongoing population-based BMI Epidemiology Study (BEST) in Gothenburg, Sweden, men born between 1945 and 1961 with information on both their childhood BMI at age 8 years and BMI change during puberty were included in the study and followed up until December, 2013. Participants who died or emigrated before age 20 years were excluded from the analysis. BMI was collected from paediatric growth charts and mandatory military conscription tests. Childhood overweight (BMI of ≥17·9 kg/m2) was defined according to the Centers for Disease Control and Prevention’s cutoff at 8 years of age, and BMI change during puberty was defined as the difference between young adult BMI and childhood BMI (BMI at age 20 years minus BMI at age 8 years). Information on mortality was retrieved from high quality national registers with the participants’ ten-digit personal identity number. We used Cox proportional hazard regression to analyse the association between exposures and mortality. The ethics committee of the University of Gothenburg, Sweden, approved the study and waived the requirement for written informed consent.
Findings: We followed 37 672 Swedish men from age 20 years for a mean of 37·8 years (1 422 185 person-years follow-up). 3188 all-cause deaths and 710 cardiovascular deaths occurred during follow-up. The correlation between childhood BMI and BMI change during puberty was marginal (r=0·06). BMI change during puberty, but not childhood BMI, was independently associated with adult all-cause and cardiovascular mortality in men. Boys that became overweight during puberty (HR 2·39; 95% CI 1·86–3·09) and boys who were overweight consistently throughout childhood and puberty (1·85; 1·28–2·67), but not boys overweight in childhood that normalised during puberty (0·99, 0·65–1·50), had increased risk of cardiovascular mortality compared with participants who were not overweight in childhood or as young adults. The association between BMI change during puberty and cardiovascular mortality was non-linear with a substantial association above a threshold of 6·7 units increase in BMI.
Interpretation: Excessive BMI increase during puberty is a risk marker of adult cardiovascular mortality. These results indicate that BMI should be monitored during puberty to identify boys with increased risk of adult cardiovascular mortality.
Claes Ohlsson, Maria Bygdell, Arvid Sondén, Annika Rosengren, Jenny M Kindblom