Trends in childhood body mass index between 1936 and 2011 showed that underweight remained more common than obesity among 398 970 Danish school children

AIM

To examine trends in all body mass index (BMI) groups in children from 1936 to 2011.

METHODS

We included 197 694 girls and 201 276 boys from the Copenhagen School Health Records Register, born between 1930 and 1996, with longitudinal weight and height measurements (6-14 years). Using International Obesity Task Force criteria, BMI was classified as underweight, normal-weight, overweight and obesity. Sex- and age-specific prevalences were calculated.

RESULTS

From the 1930s, the prevalence of underweight was stable until a small increase occurred from 1950 to 1970s, and thereafter it declined into the early 2000s. Using 7-year-olds as an example, underweight changed from 10% to 7% in girls and from 9% to 6% in boys during the study period. The prevalence of overweight plateaued from 1950 to 1970s and then steeply increased from 1970s onwards and in 1990-2000s 15% girls and 11% boys at 7 years had overweight. The prevalence of obesity particularly increased from 1980s onwards and in 1990-2000s 5% girls and 4% boys at 7 years had obesity. These trends slightly differed by age.

CONCLUSION

Among Danish schoolchildren, the prevalence of underweight was greater than overweight until the 1980s and greater than obesity throughout the period. Thus, monitoring the prevalence of childhood underweight remains an important public health issue.

Birthweight, body size, and growth during childhood and risks of rheumatoid arthritis: a large Danish cohort study

Objectives: Adult obesity may be positively associated with risks of rheumatoid arthritis (RA), but associations with early life body size are unknown. We examined whether birthweight, childhood body mass index (BMI), height, and changes in BMI and height were associated with risks of adult RA.Method: A cohort of 346 602 children (171 127 girls) from the Copenhagen School Health Records Register, born in 1930-1996, with measured weights and heights from 7 to 13 years of age, were included. Information on RA, including serological status, came from national registers from 1977 to 2017. Cox regressions were performed.Results: During a median of 35.1 years of observation time per person, 4991 individuals (3565 women) were registered with RA. Among girls, per BMI z-score, risks of RA and seropositive RA increased by 4-9% and 6-10%, respectively. Girls with overweight had higher risks of RA than girls without overweight. Girls who became overweight by 13 years of age had increased risks of RA compared to girls without overweight at 7 or 13 years (hazard ratio = 1.40, 95% confidence interval 1.19-1.66). For boys, associations between BMI and RA (including seropositive RA) were not statistically significant. Height was not associated with RA (any type) in girls. Taller boys had higher risks of RA, especially seropositive RA. Birthweight was not associated with RA.Conclusions: Among women, childhood adiposity was associated with increased risks of RA. Among men, childhood height was positively associated with risks of RA. These findings support the hypothesis that early life factors may be important in the aetiology of RA.

Childhood body mass index and height and risk of histologic subtypes of endometrial cancer

Background:

Endometrial cancer risk factors include adult obesity and taller stature, but the influence of size earlier in life is incompletely understood. We examined whether childhood body mass index (BMI; kg m⁻²) and height were associated with histologic subtypes of endometrial cancer.

Methods:

From the Copenhagen School Health Records Register, 155 505 girls born 1930–1989 with measured weights and heights from 7 to 13 years were linked to health registers. BMI and height were transformed to age-specific z-scores. Hazard ratios (HRs) and 95% confidence intervals were estimated by Cox regressions.

Results:

A total of 1020 endometrial cancers were recorded. BMI was non-linearly associated with all endometrial cancers, oestrogen-dependent cancers and the subtype of endometrioid adenocarcinomas; associations were statistically significant and positive above a z-score=0 and non-significant below zero. Compared with a 7-year-old girl with a BMI z-score=0, an equally tall girl who was 3.6 kg heavier (BMI z-score=1.5) had a hazard ratio=1.53 (95% confidence interval: 1.29–1.82) for endometrioid adenocarcinoma. BMI was not associated with non-oestrogen-dependent cancers, except at the oldest childhood ages. Height at all ages was statistically significant and positively associated with all endometrial cancers, except non-oestrogen-dependent cancers. At 7 years, per ~5.2 cm (1 z-score), the risk of endometrioid adenocarcinoma was 1.18 (95% confidence interval: 1.09–1.28). Among non-users of unopposed oestrogens, associations between BMI and endometrioid adenocarcinoma strengthened, but no effects on height associations were observed.

Conclusions:

Endometrial carcinogenesis is linked to early-life body size, suggesting that childhood BMI and height may be useful indicators for the risk of later development of endometrial cancer and might aid in the early prevention of obesity-related endometrial cancers.

Childhood height increases the risk of prostate cancer mortality

BACKGROUND

Adult body size is positively associated with aggressive and fatal prostate cancers. It is unknown whether these associations originate in early life. Therefore, we investigated if childhood height, body mass index (BMI; kg/m(2)) and growth are associated with prostate cancer-specific mortality and survival.

METHODS

Subjects were 125,208 men from the Copenhagen School Health Records Register, born 1930-1969 with height and weight measurements at ages 7-13years. Linkage to the Danish Cancer Registry and the Register of Causes of Death enabled identification of incident and fatal prostate cancers. Cox proportional hazards regressions were performed.

RESULTS

630 men had prostate cancer recorded as the underlying cause of death. Childhood height at age 13years was positively associated with prostate cancer-specific mortality (hazard ratio [HR]per z-score=1.2, 95% confidence interval [CI]: 1.1-1.3). Associations were significant at all other childhood ages. Growth analyses showed that height at age 13years had a stronger association with prostate cancer-specific mortality than height at age 7, suggesting the association at age 7 is largely mediated through later childhood height. The tallest boys at age 13years had a significantly worse survival, but only when restricted to a diagnosis at <60years of age (HRz-score of 1=1.7, 95% CI: 1.3-2.4). These associations were significant at all other childhood ages. Childhood BMI was not associated with prostate cancer mortality or survival.

CONCLUSION

Childhood height was positively associated with the hard end-point of prostate cancer-specific mortality, which strengthens prior epidemiologic observations of a positive association with prostate cancer incidence.

Childhood body mass index and the risk of prostate cancer in adult men

BACKGROUND

Prostate cancer aetiology is poorly understood. It may have origins early in life; previously we found a positive association with childhood height. The effects of early life body mass index (BMI; kg m(-2)) on prostate cancer remain equivocal. We investigated if childhood BMI, independently and adjusted for height, is positively associated with adult prostate cancer.

METHODS

Subjects were a cohort of 125208 boys formed from the Copenhagen School Health Records Register, born 1930-1969 with height and weight measurements at 7-13 years. Cases were identified through linkage to the Danish Cancer Registry. Cox proportional hazards regressions were performed.

RESULTS

Overall, 3355 men were diagnosed with prostate cancer. Body mass index during childhood was positively associated with adult prostate cancer. The hazard ratio of prostate cancer was 1.06 (95% confidence interval (CI): 1.01-1.10) per BMI z-score at age 7, and 1.05 (95% CI: 1.01-1.10) per BMI z-score at age 13. Estimates were similar and significant at all other ages. However, adjustment for childhood height attenuated the associations at all but the youngest ages as most estimates became nonsignificant.

CONCLUSIONS

These results suggest that at most childhood ages, BMI does not confer an additional risk for prostate cancer beyond that of height.