Adolescent Body Mass Index and Early Chronic Kidney Disease in Young Adulthood

Abstract

Importance: Despite increasing obesity rates in adolescents, data regarding early kidney sequelae are lacking.

Objective: To assess the association between adolescent body mass index (BMI) and early chronic kidney disease (CKD) in young adulthood (<45 years of age).

Design, setting, and participants: This cohort study linked screening data of mandatory medical assessments of Israeli adolescents to data from a CKD registry of a national health care system. Adolescents who were aged 16 to 20 years; born since January 1, 1975; medically evaluated for mandatory military service through December 31, 2019; and insured by Maccabi Healthcare Services were assessed. Individuals with kidney pathology, albuminuria, hypertension, dysglycemia, or missing blood pressure or BMI data were excluded. Body mass index was calculated as weight in kilograms divided by height in meters squared and categorized by age- and sex-matched percentiles according to the US Centers for Disease Control and Prevention. Follow-up started at the time of medical evaluation or January 1, 2000 (whichever came last), and ended at early CKD onset, death, the last day insured, or August 23, 2020 (whichever came first). Data analysis was performed from December 19, 2021, to September 11, 2023.

Main outcomes and measures: Early CKD, defined as stage 1 to 2 CKD by moderately or severely increased albuminuria, with an estimated glomerular filtration rate of 60 mL/min/1.73 m2 or higher.

Results: Of 629 168 adolescents evaluated, 593 660 (mean [SD] age at study entry, 17.2 [0.5] years; 323 293 [54.5%] male, 270 367 [45.5%] female) were included in the analysis. During a mean (SD) follow-up of 13.4 (5.5) years for males and 13.4 (5.6) years for females, 1963 adolescents (0.3%) developed early CKD. Among males, the adjusted hazard ratios were 1.8 (95% CI, 1.5-2.2) for adolescents with high-normal BMI, 4.0 (95% CI, 3.3-5.0) for those with overweight, 6.7 (95% CI, 5.4-8.4) for those with mild obesity, and 9.4 (95% CI, 6.6-13.5) for those with severe obesity. Among females, the hazard ratios were 1.4 (95% CI, 1.2-1.6) for those with high-normal BMI, 2.3 (95% CI, 1.9-2.8) for those with overweight, 2.7 (95% CI, 2.1-3.6) for those with mild obesity, and 4.3 (95% CI, 2.8-6.5) for those with severe obesity. The results were similar when the cohort was limited to individuals who were seemingly healthy as adolescents, individuals surveyed up to 30 years of age, or those free of diabetes and hypertension at the end of the follow-up.

Conclusions and relevance: In this cohort study, high BMI in late adolescence was associated with early CKD in young adulthood. The risk was also present in seemingly healthy individuals with high-normal BMI and before 30 years of age, and a greater risk was seen among those with severe obesity. These findings underscore the importance of mitigating adolescent obesity rates and managing risk factors for kidney disease in adolescents with high BMI.

Figure 1.. Construction of the Study Population

During the study period, 1 939 936 adolescents born since 1975 and aged 16 to 20 years were evaluated for eligibility for mandatory military service. Of them, 629 168 (32.4%) were insured by Maccabi Healthcare Services (MHS). Some adolescents met multiple exclusion criteria, so the overall excluded number is smaller than the simple summation of measures. Individuals diagnosed with advanced chronic kidney disease (CKD) without a prior diagnosis of early CKD were excluded from the primary analysis but were included in one secondary analysis.

Figure 2.. Incidence of Early Chronic Kidney Disease (CKD) by Adolescent Body Mass Index (BMI) Status

Life tables of early CKD incidences (and 95% CIs) according to sex, BMI (calculated as weight in kilograms divided by height in meters squared), and the population at risk in each interval. The BMI groups are indicated by color among men (A) and women (B). C. Hazard ratios of incident early CKD for the BMI groups compared with low-normal weight groups. The unadjusted model accounted for birth year. The adjusted model also included residential socioeconomic status, cognitive performance, educational level, country of birth, and mean arterial pressure.

Figure 3.. Spline Models of the Association Between Adolescent Body Mass Index (BMI) and Early Chronic Kidney Disease (CKD)

Spline models are shown for the hazard ratios (HRs) between BMI (calculated as weight in kilograms divided by height in meters squared) groups and incident early CKD. The penalized splines were adjusted for birth year, residential socioeconomic status, cognitive performance, educational level, country of birth, and mean arterial pressure. For each sex, the median of the low-normal BMI group (BMI of 19) was used as a reference. The lines indicate the HRs, and the shading indicates 95% CIs.

Figure 4.. Association Between Adolescent Body Mass Index (BMI) and Early Chronic Kidney Disease (CKD) by Diabetes and Hypertension Statuses

The incidence of early CKD is shown according to sex, BMI (calculated as weight in kilograms divided by height in meters squared) groups, and the population at risk in each interval in people who did not develop diabetes or hypertension throughout the study among men (A) and women (B). Spline models are shown for the hazard ratios (HRs) between BMI groups and incident early CKD in people who did not develop diabetes (C), hypertension (D), or either of these (E). All the models were adjusted for birth year, residential socioeconomic status, cognitive performance, educational level, country of birth, and mean arterial pressure. The median of the low-normal BMI group in each sex was used as a reference. The lines indicate the HRs, and the shading indicates 95% CIs.