Associations between muscle mass, physical activity and dietary behaviour in adolescents.

BACKGROUND AND OBJECTIVES: Investigations in older individuals suggest that adequate nutrition and physical activity are particularly important to skeletal muscle health; however, data in adolescents are scant and equivocal. The objective was to determine the associations among diet, physical activity and skeletal muscle mass in adolescents. METHODS: We assessed diet with four to seven 24-h recalls and physical activity by accelerometry in 640 adolescents. Using total body measures of fat-free soft tissue mass and fat mass assessed by dual-energy X-ray absorptiometry, the skeletal muscle mass index (SMMI) was derived by adjusting fat-free soft tissue mass for fat mass in addition to height. RESULTS: Skeletal muscle mass index (SMMI) was negatively associated with consumption of sugar-sweetened beverages (standardized beta coefficient [ß] = -0.10, P = 0.001) and saturated fats (ß = -0.28, P < 0.001). SMMI was positively associated with physical activity (moderate + vigorous) (ß = 0.20, P < 0.001). In further analysis, we observed a significant interaction between physical activity and sugar-sweetened beverage intake on SMMI (P = 0.002). CONCLUSION: Our study in adolescence suggests that physical activity and consumption of both sugar-sweetened beverages and saturated fats are associated with skeletal muscle mass. More importantly, our findings suggest that sugar-sweetened beverage intake may attenuate the beneficial effects of physical activity on skeletal muscle mass.

Insulin Resistance Negatively Influences the Muscle-Dependent IGF-1-Bone Mass Relationship in Premenarcheal Girls.

CONTEXT: IGF-1 promotes bone growth directly and indirectly through its effects on skeletal muscle. Insulin and IGF-1 share a common cellular signaling process; thus, insulin resistance may influence the IGF-1-muscle-bone relationship. OBJECTIVE: We sought to determine the effect of insulin resistance on the muscle-dependent relationship between IGF-1 and bone mass in premenarcheal girls. DESIGN, SETTING, AND PARTICIPANTS: This was a cross-sectional study conducted at a university research center involving 147 girls ages 9 to 11 years. MAIN OUTCOME MEASURES: Glucose, insulin, and IGF-1 were measured from fasting blood samples. Homeostasis model assessment of insulin resistance (HOMA-IR) was calculated from glucose and insulin. Fat-free soft tissue (FFST) mass and bone mineral content (BMC) were measured by dual-energy x-ray absorptiometry. Our primary outcome was BMC/height. RESULTS: In our path model, IGF-1 predicted FFST mass (b = 0.018; P = .001), which in turn predicted BMC/height (b = 0.960; P < .001). IGF-1 predicted BMC/height (b = 0.001; P = .002), but not after accounting for the mediator of this relationship, FFST mass. The HOMA-IR by IGF-1 interaction negatively predicted FFST mass (b = -0.044; P = .034). HOMA-IR had a significant and negative effect on the muscle-dependent relationship between IGF-1 and BMC/height (b = -0.151; P = .047). CONCLUSIONS: Lean body mass is an important intermediary factor in the IGF-1-bone relationship. For this reason, bone development may be compromised indirectly via suboptimal IGF-1-dependent muscle development in insulin-resistant children.

High sodium intake is associated with short leukocyte telomere length in overweight and obese adolescents.

BACKGROUND/OBJECTIVES: Telomere shortening has an important role in cellular aging. However, the impact of high sodium intake, an important risk factor of age-related diseases, on telomere shortening remains unknown. Therefore, we examined the relationship between high dietary sodium intake and leukocyte telomere length (LTL), particularly in the context of obesity, as obesity increases salt sensitivity. SUBJECTS/METHODS: LTL was determined by a quantitative polymerase chain reaction method in 766 adolescents aged 14-18 years (50% females, 49% African Americans). Dietary sodium intake was assessed by seven independent 24-h dietary recalls. We divided the sample into low sodium (mean 2388±522 mg per day) or high sodium groups (mean 4142±882 mg per day) based on the median value (3280.9 mg per day). RESULTS: In the entire cohort, there was no significant association between sodium intake and LTL (r=-0.05, P=0.24). However, there was a significant interaction between sodium intake and obesity status (P=0.049). Further multiple linear regression analyses revealed that higher dietary sodium intake was associated with shorter LTL in the overweight/obese group (body mass index ⩾85th percentile, ß=-0.37, P=0.04), but not in the normal-weight group (ß=0.01, P=0.93) after adjusting for multiple confounding factors. In the overweight/obese group, LTL was significantly shorter in the high sodium intake subjects vs low sodium intake subjects (1.24±0.22 vs. 1.32±0.20, P=0.02), but not the normal-weight group (1.29±0.24 vs 1.30±0.24, P=0.69). CONCLUSIONS: Higher dietary sodium intake is associated with shorter telomere length in overweight and obese adolescents.

Association of adenovirus 36 infection with adiposity and inflammatory-related markers in children.

CONTEXT: Although animal studies suggest that adenovirus 36 (Ad36) infection is linked to obesity and systemic inflammation, human data are scant and equivocal. OBJECTIVE: Associations of Ad36 infection with total body adiposity and inflammatory-related markers were determined in 291 children aged 9-13 years (50% female, 49% black). DESIGN: Fasting blood samples were measured for presence of Ad36-specific antibodies and TNF-α, IL-6, vascular endothelial growth factor (VEGF), and monocyte chemoattractant protein-1 (MCP-1). Fat mass and fat-free soft tissue mass were measured by dual-energy X-ray absorptiometry. RESULTS: The overall prevalence of Ad36 seropositivity [Ad36(+)] was 42%. There was a higher percentage of Ad36(+) children in the highest tertiles of TNF-α and IL-6 compared with their respective middle and lowest tertiles (both P < .03). There was also a trend toward a higher prevalence of Ad36(+) children in the highest tertile of VEGF compared with tertiles 1 and 2 (P = .05). Multinomial logistic regression, adjusting for age, race, sex, and fat-free soft tissue mass, revealed that compared with children with the lowest TNF-α, IL-6, and VEGF levels (tertile 1), the adjusted odds ratios for Ad36(+) were 2.2 [95% confidence interval (CI) 1.2-4.0], 2.4 (95% CI 1.4-4.0), and 1.8 (95% CI 1.0-3.3), respectively, for those in the highest TNF-α, IL-6, and VEGF levels (tertile 3). No association was observed between Ad36(+) and greater levels of fat mass or MCP-1 (all P > .05). CONCLUSIONS: In children, our data suggest that Ad36(+) may be associated with biomarkers implicated in inflammation but not with greater levels of fat mass.

25-hydroxyvitamin D, insulin-like growth factor-I, and bone mineral accrual during growth.

CONTEXT: The extent to which 25-hydroxyvitamin D [25(OH)D] and IGF-I influence bone mineral content (BMC) accrual from early to mid-puberty is unclear. OBJECTIVE, SETTING, AND PARTICIPANTS: This study sought to determine relationships among 25(OH)D, IGF-I, and BMC in community-dwelling prepubertal females (n = 76; aged 4-8 yr at baseline) over a period of up to 9 yr. DESIGN: The hypothesis that changes in IGF-I vs. 25(OH)D are more strongly associated with BMC accrual was formulated after data collection. 25(OH)D and IGF-I were log-transformed and further adjusted using two-way ANOVA for differences in season and race. Linear mixed modeling (including a random subject-specific intercept and a random subject-specific slope on age) was employed to analyze the proportion of variance the transformed 25(OH)D and IGF-I variables explained for the bone outcomes. RESULTS: IGF-I was more strongly associated with BMC accrual than 25(OH)D at the total body (R(2) = 0.874 vs. 0.809), proximal femur (R(2) = 0.847 vs. 0.771), radius (R(2) = 0.812 vs. 0.759), and lumbar spine (R(2) = 0.759 vs. 0.698). The rate of BMC accrual was positively associated with changes in IGF-I but negatively associated with 25(OH)D. When IGF-I and 25(OH)D were included in the same regression equation, 25(OH)D did not have a significant predictive effect on BMC accrual above and beyond that of IGF-I. CONCLUSIONS: These prospective data in early adolescent females indicate that both 25(OH)D and IGF-I have a significant impact on bone mineral accrual; however, the positive association of IGF-I and BMC accrual is greater than the negative association of 25(OH)D and BMC accrual.

Bone and fat relationships in postadolescent black females: a pQCT study.

UNLABELLED: Despite adolescent black females experiencing the highest rates of obesity, the effect of excess fat mass on bone structure and strength in this population is unknown. Our findings in postadolescent black females suggest that excess weight in the form of fat mass may adversely influence cortical bone structure and strength. INTRODUCTION: Although adolescent obesity has been associated with reduced bone structure and strength in white females, this relationship has not been studied in adolescent black females, a population experiencing the highest rates of obesity. Our objective was to compare bone structure and strength between postadolescent black females with normal and high levels of adiposity. METHODS: Black females with ≤ 32% body fat were classified as normal body fat (NF; n = 33, aged 19.3 ± 1.3 years); females exceeding this cutoff were classified as high body fat (HF; n = 15, aged 19.0 ± 1.1 years). Using peripheral quantitative computed tomography, tibial and radial bones were scanned at the 4% (trabecular) and 20% (cortical) sites from the distal metaphyses. Fat-free soft-tissue mass (FFST) and %body fat were assessed by dual-energy X-ray absorptiometry. RESULTS: After controlling for either FFST or body weight, the HF vs. NF group had lower total cross-sectional area (CSA; 9-17%), cortical CSA (6-15%), and strength-strain index (SSI; 13-24%) at the cortical site of the tibia (all p < 0.05). At the cortical site of the radius, the HF vs. NF group had lower total CSA (14%, p = 0.03), cortical CSA (9%, p = 0.04), and SSI (15%, p = 0.07) after control for body weight. There were no group differences in either the FFST-adjusted cortical bone values at the radius or in the trabecular bone parameters (body weight- or FFST-adjusted) at the tibia and radius. CONCLUSIONS: Consistent with our adiposity and bone data in late-adolescent white females, our findings in black females entering adulthood also suggest that obesity may adversely influence cortical bone strength.

Former college artistic gymnasts maintain higher BMD: a nine-year follow-up.

INTRODUCTION: If higher bone gains acquired from weight-bearing sports during growth persist into old age, the residual benefits could delay or even prevent osteoporotic fractures. The purpose of this study was to determine if the higher areal bone mineral density (aBMD) observed 15 years after competitive training and competition in former female college artistic gymnasts (GYM) compared with controls (CON) is maintained nine years later in this same cohort approaching menopause. In this 9-year follow-up, aBMD changes were also compared between GYM (n=16; aged 45.3+/-3.3 years) and CON (n=13; aged 45.4+/-3.8 years). METHODS: Total body, lumbar spine, proximal femur, femoral neck, leg, and arm aBMD were assessed at baseline and follow-up using dual-energy X-ray absorptiometry (DXA), (Hologic QDR-1000W). GYM had higher aBMD at all sites at follow-up (P<0.05; eta (2)>0.14). RESULTS: While there were no significant differences between groups for percent changes in aBMD at the total body, lumbar spine, total proximal femur, femoral neck, and arm, the change in leg aBMD was significantly different between GYM and CON (P=0.05; eta (2)=0.14). CONCLUSIONS: Former female college artistic gymnasts maintained significantly higher aBMD than controls 24 years after retirement from gymnastics training and competition. This study provides greater insight into the effects of past athletic participation on skeletal health in women approaching menopause.

Fluoxetine in adolescents with major depression and an alcohol use disorder: an open-label trial.

Recently, a first placebo-controlled study of an selective serotonin reuptake inhibitor (SSRI) medication was conducted among a sample of adolescents with major depression by Emslie et al. [Arch. Gen. Psychiatry 54 (1997) 1031.]. That study demonstrated efficacy for fluoxetine vs. placebo for treating adolescents with major depression. However, to date, no studies have been conducted to assess the efficacy of fluoxetine or any other SSRI medication in adolescents with major depression in combination with an alcohol use disorder (AUD). In this study, the authors investigated whether fluoxetine decreases the depressive symptoms and the drinking of adolescents with comorbid major depression and an AUD. The authors conducted a 12-week open-label study of fluoxetine (20 mg) in 13 adolescents with current comorbid major depression and an AUD. A significant within-group decrease (improvement) was found for both depressive symptoms and drinking during the course of the study. The fluoxetine was well tolerated during the study. These data suggest promise for fluoxetine for decreasing both the depressive symptoms and the drinking of adolescents with comorbid major depression and an AUD.

Course of functioning in adolescents 1 year after alcohol and other drug treatment.

Clinical course was studied in 131 male and female adolescents with current alcohol use disorder (AUD) at baseline (BL). Participants were classified into 4 groups according to their diagnosis and drinking pattern 1 year later. The 4 groups were compared with each other and with 37 community control participants. Results showed that over half of the clinical sample no longer had a current AUD at 1 year; about 64% were and 36% were not still drinking. BL discriminators of 1-year status were alcohol dependence, other drug use, and coping. All of the clinical groups tended to show improvement at 1 year in the main dependent variables, and the abstainers' level of drug use and coping were comparable with that of the community participants. These findings suggest that many adolescents improve in functioning during the 1 year after alcohol and drug treatment and that a stress and coping model is useful for studying clinical course of AUDs in adolescents.

Toward the DSM-V: the Withdrawal-Gate Model versus the DSM-IV in the diagnosis of alcohol abuse and dependence.

The Diagtnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 1994) classifies as dependent many cases of mild alcohol problems. DSM-IV diagnoses have modest relationships with predictive and some concurrent validators and often improperly sequence the onset of abuse versus dependence, perhaps due to insufficient emphasis on physiological features. Testing reliability, syndrome prevalence, syndrome sequencing, and concurrent and predictive validity, this study contrasted the DSM-IV with the Withdrawal-Gate Model (WGM), in which alcohol withdrawal is necessary and sufficient for the dependence diagnosis. Clinical samples of adults (baseline n = 318) and adolescents (baseline n = 214) meeting abuse or dependence were assessed for DSM-IV alcohol symptoms and external measures of problem severity and reinterviewed at 6 (adults) and 12 months (adults and adolescents). Among DSM-IV dependent cases, the WGM shifted 32% of adults and 80% of adolescents to the abuse category, making both categories more symptomatically severe, but had a negligible effect on the prevalence of total alcohol diagnoses. The WGM was more reliable than the DSM-IV and temporally sequenced abuse before dependence in a greater number of cases. The WGM was superior to the DSM-IV in concurrent and predictive validity on most measures. Future diagnostic systems may be more reliable and valid if they require evidence of withdrawal for substance dependence.

Inter-rater reliability of the SCID alcohol and substance use disorders section among adolescents.

Diagnostic interviews for substance use disorders tend to have high reliability among adults. We examined the inter-rater reliability of the substance use disorders section of the Structured Clinical Interview for the DSM, using 46 male and 25 female adolescent drinkers recruited from community and treatment sources. Inter-rater reliability was high for individual DSM-IV alcohol symptoms (kappa=0.84-1.0) and diagnoses (kappa=0.94), and for other substance use disorder diagnoses (kappa=0.82-1.0).

Gender differences and similarities in the personality correlates of adolescent alcohol problems.

The personality traits of behavioral under-control (BU) and negative emotionality (NE) are associated with alcohol problems. The authors examined gender differences in the associations of BU and NE with alcohol problems in 710 adolescents recruited from community and treatment sources. Multiple measures were used to characterize each construct, and the specified 2-factor model provided a reasonably good fit to the data. ANCOVAs were used to examine each construct by gender across four groups: never-regular drinkers, regular drinkers, and those with DSM-IV alcohol abuse and alcohol dependence. Males had significantly higher BU and lower NE than did females. BU and NE both increased with degree of alcohol problems. However, there was not a significant Gender x Alcohol Group interaction for BU or NE. Although there are gender differences in levels of BU and NE, mechanisms of alcohol involvement related to these 2 personality traits may operate similarly in adolescent males and females.

Diagnostic concordance of DSM-III, DSM-III-R, DSM-IV and ICD-10 alcohol diagnoses in adolescents.

OBJECTIVE: Little is known about the validity of diagnostic criteria for alcohol use disorders (AUDs) when applied to adolescents. This study examined the diagnostic concordance of DSM-III, DSM-III-R, DSM-IV and ICD-10 AUDs in a sample of adolescents with a broad range of alcohol problem severity. METHOD: Participants were 413 adolescents (250 male), ages 13 to 19, drawn from clinical and community sources. AUDs were assessed using the Structured Clinical Interview for the DSM (SCID), modified to make diagnoses in the four nosological systems. Diagnostic agreement for lifetime diagnoses was quantified with the kappa statistic. RESULTS: Agreement was fair to high across the three categories of alcohol dependence, alcohol abuse and no alcohol diagnosis (kappa = 0.51 to 0.76); for alcohol dependence (kappa = 0.51 to 0.83); and for the categories of any AUD versus no AUD (kappa = 0.55 to 0.96). Concordance was very low for alcohol abuse diagnoses (kappa = 0.10 to 0.23), with the exception of DSM-III-R and DSM-IV (kappa = 0.62). Dependence was superior to abuse in the degree of temporal overlap in diagnostic agreements. CONCLUSIONS: Similar to findings with adults, diagnostic concordance among adolescents tended to be fair to high for alcohol dependence and very low for alcohol abuse. The data highlight the inconsistency across nosological systems in the conceptual framework and definition of the alcohol abuse category.

Reliability and concurrent validity of DSM-IV subclinical symptom ratings for alcohol use disorders among adolescents.

BACKGROUND: The concurrent validity of subclinical ratings for psychiatric symptoms can help refine symptom definitions and threshold criteria. However, virtually no research has examined subclinical ratings for DSM-IV symptoms in psychiatric diagnostic interviews. This study examined the frequency, reliability, and concurrent validity of subclinical ratings for 11 symptoms of alcohol use disorders among adolescents. METHODS: Subjects were 239 male and 164 female adolescents ages 14 to 18 recruited from treatment and community sources. Symptoms and diagnoses were made with an adapted version of the Structured Clinical Interview for the DSM-IV. RESULTS: Subclinical ratings showed acceptable to high interrater reliability. The proportion of subclinical ratings tended to decrease with increasing levels of alcohol problems. For 10 of the 11 symptoms, subjects with subclinical ratings were distinguished from those with absent and/or those with present ratings. Subjects with subclinical ratings were often distinct from those with present ratings but less often distinct from those with absent ratings. CONCLUSIONS: For most of the DSM-IV alcohol use disorder symptoms, subclinical ratings appear to be reliable and valid and provide information beyond dichotomous symptom classifications for adolescents. Threshold criteria appear to be appropriate in many cases, but boundaries between absent and subclinical ratings are "fuzzy." Practical and research implications are discussed.

Risky sexual behaviors among adolescents with alcohol use disorders.

Little is known about risky sexual activity among adolescents with alcohol use disorders. This study of 371 adolescent drinkers found that those with alcohol disorders were more likely than other drinkers to be sexually active, to have greater numbers of partners, and to initiate sexual activity at slightly younger ages. Independent of alcohol group, females were more likely than males to have unprotected sexual encounters.

Diagnostic orphans: adolescents with alcohol symptom who do not qualify for DSM-IV abuse or dependence diagnoses.

OBJECTIVE: Little is known about the validity of the DSM-IV criteria for alcohol use disorders when applied to adolescents. This report describes a group of "diagnostic orphans," adolescents with one or two DSM-IV alcohol dependence symptoms who do not meet the DSM-IV criteria for alcohol abuse or alcohol dependence. METHOD: The study included 199 male and 173 female subjects aged 13-19 years. All subjects were regular drinkers, recruited from community sources and alcohol treatment programs. At baseline and at 1-year follow-up, DSM-IV alcohol use disorders were assessed with a version of the Structured Clinical Interview for DSM-III-R, modified for DSM-IV criteria. RESULTS: Diagnostic orphans represented 31% of the drinkers without an alcohol use disorder. The orphans were similar to the alcohol abusers and dissimilar to the other drinkers in alcohol and substance use patterns and in the course of alcohol problems over 1 year. CONCLUSIONS: The results indicate limitations of the DSM-IV criteria for alcohol use disorders when applied to adolescents. Diagnostic orphans should be considered separately from other drinkers in research and treatment efforts.