Association of Body Size at Birth and Childhood Growth With Hip Fractures in Older Age: An Exploratory Follow-Up of the Helsinki Birth Cohort Study

Is there an association between birth characteristics and fractures in young adults? The HUNT Study, Norway

This population study investigated the association between birth characteristics and fracture risk in 11,099 young adults (aged 19-54 years). Our findings indicate that birth weight, gestational age, and birth weight for gestational age were not associated with fractures in the wrist, humerus, hip, and spine in this population.

PURPOSE

Skeletal development starts during fetal life, and it is estimated that most bone formation occurs in the 3rd trimester. This study examined the association between birth characteristics and fractures of the wrist, humerus, hip, and spine, in young adults (19-54 years).

METHODS

11.099 participants in the 3rd survey of the HUNT Study (2006-2008) were linked with the Medical Birth Registry of Norway and hospital records. Fractures of the wrist, humerus, hip, and spine were identified using ICD9/10 codes between 1988 and 2021. Follow-up was from date of participation in HUNT until a first fracture, emigration, death, or end of study. Cox regression was used to estimate hazard ratios (HR) of fracture associated with birth characteristics (95% CI), adjusted for birth year, sex, maternal age, and maternal morbidity. In a secondary analysis, follow-up started in 1988.

RESULTS

During a median follow-up of 14.0 years (153,657 person-years), 290 fractures occurred. Mean age at first fracture was 41.4 years (SD 7.4). Overall, there were no clear associations between birth characteristics and fractures in these data. HR for fracture was 0.43 (0.15-1.24) for those with a birth weight < 2.5 kg (reference birth weight 3.5 - 3.9 kg); 1.04 (0.74 - 1.46) for those born small for gestational age (< 10th percentile, reference 10 - 90th percentile); and 0.63 (0.33 - 1.23) for those born preterm (reference term births). The secondary analysis from 1988, including 539 fractures, gave similar results as the main analysis.

CONCLUSION

Birth weight, gestational age, or birth weight for gestational age was not associated with an increased risk of fractures of the wrist, humerus, hip, and spine in young adults.

Early-life famine exposure, adulthood obesity patterns, and risk of low-energy fracture

Malnutrition in early life increases the risk of osteoporosis, but the association of early-life undernutrition combined with adulthood obesity patterns with low-energy fracture remains unknown. This study included 5323 community-dwelling subjects aged ⩾40 years from China. Early-life famine exposure was identified based on the participants' birth dates. General obesity was assessed using the body mass index (BMI), and abdominal obesity was evaluated with the waist-to-hip ratio (WHR). Low-energy fracture was defined as fracture occurring after the age of ⩾40 typically caused by falls from standing height or lower. Compared to the nonexposed group, the group with fetal, childhood, and adolescence famine exposure was associated with an increased risk of fracture in women with odds ratios (ORs) and 95% confidence intervals (CIs) of 3.55 (1.57-8.05), 3.90 (1.57-9.71), and 3.53 (1.05-11.88), respectively, but not in men. Significant interactions were observed between fetal famine exposure and general obesity with fracture among women (P for interaction = 0.0008). Furthermore, compared with the groups with normal BMI and WHR, the group of women who underwent fetal famine exposure and had both general and abdominal obesity had the highest risk of fracture (OR, 95% CI: 3.32, 1.17-9.40). These results indicate that early-life famine exposure interacts with adulthood general obesity and significantly increases the risk of low-energy fracture later in life in women.

Early childhood as a sensitive period for the effect of growth on childhood bone mass: Evidence from Generation XXI birth cohort

BACKGROUND

To identify sensitive periods for the effect of early life growth on childhood bone mass we compared the associations between weight and length/height velocities from birth to age six and bone mineral content (BMC) and areal density (aBMD) at 7 years of age.

METHODS

We analyzed data from 1853 participants from the Generation XXI birth cohort scanned with a whole body dual-energy X-ray absorptiometry system. Velocities of growth in weight and length/height were obtained through linear spline multilevel models on the basis of data collected during routine health examinations. Using linear regression we computed associations of birth weight, birth length, five weight velocities ("early neonatal": 0-10 days, "early infancy": 10 days-3 months, "late infancy": 3-12 months, "early childhood": 1-3 years, and "later childhood": 3-6 years) and four length/height velocities ("early infancy": 0-3 months, "late infancy": 3-12 months, "early childhood": 1-3 years, and "later childhood": 3-6 years) with outcomes BMC, aBMD, height and height-adjusted BMC at age seven. Confounding by maternal and child characteristics was addressed and effects of growth velocities were adjusted to preceding growth.

RESULTS

Weight and length/height velocities up to the age of six were associated with increased bone mass, areal density and height at 7 years with the strongest associations observed for growth in early childhood. In this age period, after concurrent height and confounder adjustment, one standard deviation (SD) increase in weight velocity was associated with higher BMC z-scores: 0.27 (95%CI: 0.22, 0.32) in girls and 0.24 (95%CI: 0.19, 0.29) in boys. Height velocity was also associated with greater height-adjusted BMC z-score: 0.12 (95%CI: 0.07, 0.17) per SD in girls and 0.11 (95%CI: 0.06, 0.16) in boys. The pattern of associations was similar, albeit attenuated, after adjusting for preceding growth.

CONCLUSION

Growth in second and third years of life may represent a sensitive period for the effect of growth on childhood bone mass, partly through their effect on concurrent body size.

How Is Adolescent Bone Mass and Density Influenced by Early Life Body Size and Growth? The Tromsø Study: Fit Futures-A Longitudinal Cohort Study From Norway

The effect of birth weight and childhood body mass index (BMI) on adolescents’ bone parameters is not established. The aim of this longitudinal, population‐based study was to investigate the association of birth weight, childhood BMI, and growth, with adolescent bone mass and bone density in a sample of 633 adolescents (48% girls) from The Tromsø Study: Fit Futures. This population‐based cohort study was conducted in 2010–2011 and 2012–2013 in Tromsø, Norway. Bone mineral content (BMC) and areal BMD (aBMD) were measured at total hip (TH) and total body (TB) by dual‐energy X‐ray absorptiometry (DXA) and converted to internal Z‐scores. Birth weight and childhood anthropometric measurements were retrospectively obtained from the Medical Birth Registry of Norway and childhood health records. Associations between birth weight, BMI, and growth were evaluated by fitting linear mixed models with repeated measures of BMC and aBMD at ages 15 to 17 and 18 to 20 years as the outcome. In crude analysis, a significant positive association (p < 0.05) with TB BMC was observed per 1 SD score increase in birth weight, observed in both sexes. Higher rate of length growth, conditioned on earlier size, from birth to age 2.5 years, and higher rate of weight gain from ages 6.0 to 16.5 years, conditioned on earlier size and concurrent height growth, revealed stronger associations with bone accrual at ages 15 to 20 years compared with other ages. Compared with being normal weight, overweight/obesity at age 16.5 years was associated with higher aBMD Z‐scores: β coefficient (95% confidence interval [CI]) of 0.78 (0.53, 1.03) and 1.08 (0.85, 1.31) in girls, 0.63 (0.42, 0.85) and 0.74 (0.54, 0.95) in boys at TH and TB, respectively. Similar associations were found for BMC. Being underweight was consistently negatively associated with bone parameters in adolescence. In conclusion, birth weight influences adolescent bone mass but less than later growth and BMI in childhood and adolescence. © 2018 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research

Epigenetics of Skeletal Diseases

PURPOSE OF REVIEW

Epigenetic mechanisms modify gene activity in a stable manner without altering DNA sequence. They participate in the adaptation to the environment, as well as in the pathogenesis of common complex disorders. We provide an overview of the role of epigenetic mechanisms in bone biology and pathology.

RECENT FINDINGS

Extensive evidence supports the involvement of epigenetic mechanisms (DNA methylation, post-translational modifications of histone tails, and non-coding RNAs) in the differentiation of bone cells and mechanotransduction. A variety of epigenetic abnormalities have been described in patients with osteoporosis, osteoarthritis, and skeletal cancers, but their actual pathogenetic roles are still unclear. A few drugs targeting epigenetic marks have been approved for neoplastic disorders, and many more are being actively investigated. Advances in the field of epigenetics underscore the complex interactions between genetic and environmental factors as determinants of osteoporosis and other common disorders. Likewise, they help to explain the mechanisms by which prenatal and post-natal external factors, from nutrition to psychological stress, impact our body and influence the risk of later disease.

Sexual Dimorphism and the Origins of Human Spinal Health

Recent observations indicate that the cross-sectional area (CSA) of vertebral bodies is on average 10% smaller in healthy newborn girls than in newborn boys, a striking difference that increases during infancy and puberty and is greatest by the time of sexual and skeletal maturity. The smaller CSA of female vertebrae is associated with greater spinal flexibility and could represent the human adaptation to fetal load in bipedal posture. Unfortunately, it also imparts a mechanical disadvantage that increases stress within the vertebrae for all physical activities. This review summarizes the potential endocrine, genetic, and environmental determinants of vertebral cross-sectional growth and current knowledge of the association between the small female vertebrae and greater risk for a broad array of spinal conditions across the lifespan.