Sleep duration and its association with cardiometabolic outcomes among adolescents enrolled in the SI Program in Spain
Authors: Martinez-Gomez J , Fernandez-Alvira J M , De Cos-Gandoy A , Bodega P , De Miguel M , Carral V , Laveriano-Santos E P , Tresserra-Rimbau A , Carvajal I , Estruch R , Lamuela-Raventos R M , Santos-Beneit G , Fuster V , Fernandez-Jimenez R 
Published: October 2022

Abstract

Background
Sleep duration has been inversely associated with increased prevalence of overweight/obesity in childhood and adolescence [1, 2]. However, large studies linking over time objectively measured sleep duration and other cardiometabolic outcomes in adolescence are lacking.

Purpose
To evaluate sleep duration and its association with cardiometabolic outcomes in a large cohort of adolescents aged 12 to 16 years from the SI! Program for Secondary Schools trial in Spain [3], together with its relationship with sociodemographic variables.

Methods
Seven-day actigraphic recording was performed in 1229 adolescents at baseline (49.7% girls; 12.5 (0.4) years), 1058 at first follow-up (51.1% girls; 13.9 (0.4) years), and 895 at second follow-up (52.3% girls; 15.8 (0.4) years). Three groups were defined: very short sleep duration (&lt;7 h), short sleep duration (7 to 8 h), and reference sleep duration (≥8 h) [4]. Overweight/obesity were determined according to BMI age- and sex-adjusted percentiles. Continuous Metabolic Syndrome (MetS) score was calculated as the sum of the age-and-gender specific z-scores of mean arterial pressure (MAP) (MAP = ((systolic BP − diastolic BP)/3) + diastolic BP), waist circumference, and fasting blood measures of high-density lipoprotein cholesterol (HDL-c) levels multiplied by −1, triglycerides, and glucose levels [5]. Associations between sleep duration and cardiometabolic outcomes were analyzed using generalized linear and Poisson distribution adjusted models.

Results
At 12 years of age, only 34.2% of the adolescents met sleep recommendations (sleep hours ≥8), and this percentage decreased with advancing age (23.4% and 19.4% at approximately 14 and 16 years of age, respectively) (Figure 1). Boys and individuals from migrant families tended to sleep shorter. Moreover, sleep duration was directly associated with sleep quality and efficiency. After adjusting for potential cofounders, very short sleepers (&lt;7h) had a higher prevalence ratio (PR) of overweight/obesity at baseline (PR: 1.21 [95% CI: 1.16 to 1.27]) and at first follow-up (PR: 1.72 [95% CI: 1.08 to 2.74]) than the reference group (≥8 h) (Figure 2). Similarly, very short sleepers showed higher mean MetS scores at baseline (0.98 [95% CI: 0.43 to 1.54] and at first follow-up (0.76 [95% CI: 0.24 to 1.27]) as compared with the reference group. Short sleepers showed similar trends with associations of weaker magnitude, as they were the overall associations between sleep duration and cardiometabolic outcomes at second follow-up.

Conclusions
Most adolescents, and particularly those with a migrant background, did not meet sleep recommendations. Moreover, a shorter sleep duration was associated with cardiometabolic outcomes, particularly at 12 and 14 years of age and when sleeping less than 7 hours. Health promotion programs should emphasize the importance of good sleep habits.

Funding Acknowledgement
Type of funding sources: Other. Main funding source(s): 1. Fundaciό la Maratό de TV3.2. SHE Foundation and “la Caixa” Foundation.