Health-related quality of life (HRQoL) is a holistic measure of health and encompasses a general sense of well-being related to physical, psychological, environmental, and social aspects of health [1
]. As HRQoL comprises positive subjective aspects of well-being and covers several aspects of what each person considers important in life, such as having adequate relationships with family and peers, feeling fit and well in the physical aspect, and being satisfied with material needs, it is desirable that all population subgroups have adequate HRQoL [3
]; however, adolescence often includes physical, behavioral, and psychosocial changes that can negatively affect HRQoL [2
Health-related lifestyle is a determinant of HRQoL [5
] constituted by many behaviors (e.g., physical activity, screen time, diet, sleep, use of alcohol, tobacco, and other substances) that can positively or negatively affect peoples’ way of life and health [7
], and contribute to the protection or risk for early mortality and chronic diseases [8
]. Adequate sleep has been associated with better HRQoL [9
]. Additionally, recent reviews showed that physical activity [6
] and screen time [12
] have been positively and negatively related to HRQoL, respectively, and sports practice has shown to be even better for some of its dimensions [10
]. Furthermore, a Mediterranean diet pattern has been related to increased HRQoL scores [6
], and alcohol [14
], tobacco [17
], and illicit drug [15
] use seem to be negatively related to HRQoL. Many of the lifestyle behaviors, when adopted in an unhealthy way, have responses that may negatively impact health in ways that compromise HRQoL. For example, lack of sleep affects emotional regulation and cognitive performance [18
], use of substances is associated with increased anxiety [19
], and high use of social media has been associated with social harassment [20
] and depressive symptoms [21
Identifying modifiable lifestyle factors that are related to HRQoL is necessary to plan effective policies and interventions in adolescence since it is the period where different behaviors are adopted and may track into adulthood. Furthermore, most previous studies have focused on one or two [22
] behaviors of the lifestyle, such as physical activity [11
], sleep [23
], or screen time [12
], but have not considered the others, which limits our comprehension of what factors are associated independent of the others (e.g., the relationship between sedentary behavior and HRQoL may not be independent of physical activity). Additionally, the majority of the available evidence is from high-income countries [11
], which differs from low- and middle-income countries in social and cultural aspects that may impact the lifestyle [24
] and HRQoL of adolescents. Brazilian adolescents have been shown to be physically inactive [25
] while also experimenting and using substances early [26
], as well as having the highest prevalence of unhealthy screen time behavior in a comparison of 12 countries [27
]. These behaviors have been shown to affect adolescents’ health, including depressive symptoms [28
], and their relation with HRQoL should be evaluated. Thus, the present study aimed to analyze the association between lifestyle behaviors and HRQoL in a sample of Brazilian adolescents while considering other lifestyle behaviors in the analyses.
This study reports the association between lifestyle behaviors and HRQoL in a sample of Brazilian high school adolescents. In the initial analyses, we observed that a lower volume of sports, eating processed foods, working on a screen device, watching videos, playing videogames, using social media, having experimented with illicit drugs, smoking, and sleeping insufficiently were associated with lower HRQoL. However, after adjustments for other behaviors, we observed that only the volume of sports, eating processed foods, working on a screen device, having experimented with illicit drugs, and sleeping insufficiently were significantly associated with lower HRQoL independently of other behaviors. This suggests that multiple lifestyle factors are important when HRQoL is concerned, and from a holistic approach, interventions targeting multiple behaviors may be needed to improve the well-being of adolescents. We believe the findings of this study expand our understanding of the etiology of HRQoL in adolescents of middle-income countries and provide insights for possible interventions.
The relationship between physical activity and HRQoL in adolescents has been shown in a previous review [11
]; however, the effect sizes for cross-sectional studies are small to negligible. One hypothesis is that some activities, such as sports, are more important for HRQoL than others (e.g., doing chores), which is supported by a recent study in adolescents that showed that sports activities were more strongly related to HRQoL than non-sport activities [10
]. These results are similar to the ones observed in the present study that despite a small effect size, may be important if participants engage in it an hour every day. It is important to notice that this relationship was still significant after adjustment for other lifestyle behaviors, suggesting that increasing participation in sports may be an effective way to increase HRQoL even when other behaviors are not changed. This could improve interventions based on physical activity for the improvement of HRQoL in pediatric populations, which so far have shown modest effects [11
Findings regarding screen time behaviors suggest that only working for more than four hours a day remained associated with lower HRQoL after adjustment for other lifestyle behaviors. This finding suggests that it may not be the screen time that negatively affects HRQoL but rather the increased workloads, as participants who have to work for longer hours, combined with school homework, may have less leisure time available compared to those who do not work.
In relation to sleep, a previous study with 9–11-year-olds from 12 countries also found no association between accelerometer-measured sleep indicators with HRQoL assessed with the Kidscreen 10 [36
]. Concerning sleep, short sleepers had lower scores of HRQoL compared to healthy sleepers in the present study. This finding is similar to other studies with adolescent samples [9
]. Sleep is an important behavior for many body systems, and poor sleep has been associated with impaired emotional regulation and cognitive performance [18
], which can be a pathway that at least partly explains the relationship with HRQoL.
Eating processed foods was related to lower HRQoL in the present study, whereas the unprocessed food score was not. The relationship between diet and HRQoL has been studied before, and a Mediterranean diet has been associated with better scores of HRQoL in adolescents [6
]. In the present study, we adopted a data-driven approach to identify dietary patterns, which revealed two scores that reflected processed and unprocessed foods, and do not directly compare to adherence to the Mediterranean diet. However, it is important to notice that the low consumption of processed foods is a defining characteristic of the Mediterranean diet, is associated with better health outcomes [37
], and is recommended by current dietary guidelines for the Brazilian population [38
]. Increased consumption of ultra-processed foods, in particular, has been shown to be associated with many unhealthy outcomes, such as obesity, diabetes, and cancer [33
], and although its mechanisms and pathways are not clear, this may partially explain its relationship with HRQoL observed in the present study.
Drug experimentation was associated with lower HRQoL in the present sample, as observed in adolescent samples in previous studies [15
]. This relationship is not clear, and one possible explanation is that other non-observed variables predispose adolescents to health-risking behaviors (e.g., experimenting with drugs, aggressive behavior, high-risk sexual behavior) that are also associated with lower HRQoL, but some were not investigated in the present study [15
]. This hypothesis, however, would suggest that alcohol and tobacco are associated with HRQoL, which was not observed in the present study. Additionally, adolescents with low HRQoL may try substances in a way to cope with the problems, but, to confirm this, prospective studies are needed.
Although some lifestyle behaviors, such as the use of social media and cigarette smoking, were observed to be associated with HRQoL in the crude models, the association was no longer statistically significant after mutual adjustment with other behaviors. Previous studies have shown that some of these behaviors were associated with HRQoL in adolescent samples; however, this relationship is not necessarily independent of other behaviors (e.g., the association between social media and HRQoL may not be independent of physical activity), and in many of these studies, independence may have not been tested by including several lifestyle behaviors in the analytical models. Future longitudinal studies could adopt structural equation modeling techniques to check if changes in lifestyle behaviors are related to each other and impact HRQoL. Overall, the results of the present study suggest that policies and interventions should target multiple behaviors, including sleep, diet, physical activity, and the prevention of drug use, to increase adolescents’ HRQoL.
Whereas no significant sex interaction terms were observed for the associations of lifestyle behaviors and HRQoL, boys had higher scores compared to girls. The sex difference observed in the present study is consistent with current literature [10
], with girls being more susceptible to perceive their health as poor, having functional limitations, increased depressive symptoms, and low self-esteem [39
]. Girls may have increased social pressures and hormonal changes that increase their sensibility to stress during adolescence [40
], which predisposes them to depression as well. Additionally, whereas no interactions were observed, physical activity was related to HRQoL in this and previous studies [10
], and girls systematically engage in less physical activity compared to boys [41
]. This illustrates that intervening in lifestyle behaviors among girls may also provide additional benefits that can improve HRQoL.
The findings of the present study suggest that several lifestyle factors are related to adolescents’ HRQoL. Our findings can be useful in the planning of policies, and interventions should be taken into account in future studies. For example, intervention studies or school managers aiming at improving HRQoL of adolescents may have success if improvements in sports participation (e.g., offering classes) and reduction of the ingestion of processed food (e.g., changing cafeteria policies) occur. Additionally, longitudinal and experimental studies are needed to confirm the direction of the associations observed in our study. Another important aspect to be considered in future research is to explore how other variables, such as self-esteem, environmental factors, and family and peer relations, can influence HRQoL and may interact with lifestyle behaviors.
This study has limitations to be acknowledged. The sample was small in relation to the large scope of associated exposures. Self-report instruments were used to measure habitual behaviors, which may be prone to recall limitations and social desirability bias. However, qualitative aspects of behaviors were explored, including the types of screen time behaviors and physical activity, which are still a challenge to be objectively measured. A single overall measure of HRQoL was evaluated in this study, which limited the understanding of findings, as HRQoL is a complex latent construct that can be analyzed in distinct dimensions by instruments with a higher number of items. The main strength of this study was the provision of a comprehensive analysis of the associations between several lifestyle behaviors and HRQoL by exploring qualitative aspects of measured behaviors, and among adolescents of a middle-income country, while taking into account the other behaviors in our analyses.