Overweight and obesity in adolescence secular trends and associations with perceived weight, sociodemographic factors and screen time

Abstract

Tutkimuksen perusteella ylipainoisten suomalaisnuorten osuus kolminkertaistui vuodesta 1977 vuoteen 2005. Ylipainoisuus oli harvinaisempaa suurimmissa kaupungeissa asuvilla, lukiolaisilla, niillä jotka kokivat menestyvänsä koulussa keskitasoa paremmin sekä korkeimmin koulutettujen vanhempien lapsilla. Näiden tekijöiden merkitys ei muuttunut tutkimusjakson aikana. Kaikkien nuorten paino ei ole lisääntynyt, mutta lihavimmat ovat entistä lihavampia. Samana ajanjaksona itsensä ylipainoiseksi kokeminen väheni sekä ylipainoisten että normaalipainoisten nuorten joukossa. Ylipainoisuus oli yleisempää erityisesti tytöillä, jotka käyttivät enemmän aikaa television tai tietokoneen ääressä. Tulosten perusteella ei voi päätellä, oliko ylipainoisuus runsaamman television katsomisen ja tietokoneen käytön syy vai seuraus. Digitaalisten pelien pelaaminen ei ollut yhteydessä ylipainoisuuteen.

Samanlaisia tuloksia nuorten painokehityksestä on saatu lähes kaikkialla maailmassa. Ylipainoisuuden yleistyminen on huolestuttavaa, koska ylipainoisuus lisää psykososiaalisia ongelmia ja sydän- ja verisuonitautien riskitekijöitä jo lapsuusiässä sekä muun muassa sydän- ja verisuonitauteja sekä tyypin 2 diabetesta myöhemmällä iällä.

LL Susanna Kautiaisen väitöskirjassa selvitettiin suomalaisnuorten ylipainoisuuden ja oman painon kokemisen muutoksia sekä niihin vaikuttavia tekijöitä vuosien 1977 ja 2005 välisenä aikana. Osana tutkimusta arvioitiin ruutuajan eli television, tietokoneen ja digitaalisten pelien parissa vietetyn ajan yhteyttä ylipainoisuuteen. Tutkimuksen aineistona olivat Nuorten terveystapatutkimukseen vuosina 1977 2005 osallistuneet 90 000 nuorta, jotka olivat kyselyyn vastatessaan 12-, 14-, 16- ja 18-vuotiaita.

The aim of this dissertation was to describe secular changes in overweight,obesity and perceived weight in Finnish adolescents, to study sociodemographic differences in the prevalence of overweight over time, and to assess the associations of overweight and obesity with the usage of different forms of information and communication technology. The data were collected as part of a Finnish nationwide monitoring system of adolescence health and health behaviours, the Adolescent Health and Lifestyle Survey. Self-administered questionnaires were sent to 12-, 14-, 16- and 18-year-old adolescents every second year from 1977 to 2005. The numbers of respondents in each survey year varied between 2 832 and 8 390. The response rates declined from 88% to 66% over the study period.

The first aim was to describe the secular changes in overweight and obesity, and the changes in the overall body mass index (BMI) distribution of Finnish 12 to 18-year-old adolescents over two decades (1977 1999). BMI was based on selfreported weight and height, and overweight and obesity were defined according to the International Obesity Task Force (IOTF) criteria. There was a steady rise in overweight and obesity from 1977 to 1999, resulting in a 2 to 3-fold increase in the prevalence between the first and the last study year. An important finding was that, during the same time period, the increase in BMI was considerably larger at the upper end of the BMI distribution, while hardly any change was observed at the lower end.

The second aim was to examine whether the secular changes (between 1979 and 2005) in the prevalence of overweight and obesity were different in various sociodemographic subgroups of the Finnish 12 to 18-year-old adolescents. The study showed that the increase in overweight and obesity observed in study I continued further to 2005. Generally, no different patterns in the relative increase in the prevalence of overweight during the 26-year study period were observed between sociodemographic subgroups of Finnish adolescents, regardless of which of the several factors measuring demography as well as parental and adolescent s own socioeconomic status were used.

The third aim was to evaluate whether perceived weight and its association with self-reported weight have changed among Finnish 12 to 18-year-old adolescents over 20 years (1979 1999). The proportion of adolescent boys perceiving themselves as being overweight remained stable over the study period in the total group, while it decreased among overweight and normal weight boys. Among girls, a decreasing trend was seen both in the total group and among normal weight and overweight subjects.

The fourth aim was to study whether the time spent on different forms of information and communication technology was associated with overweight and obesity among Finnish 14 to 18-year-old adolescents in the 2001 survey. The main novelty of the study was our ability to explore separately the times spent on television, digital games, and especially computer (e-mail, writing and surfing). We found that an increase in time spent on viewing television and using computer were associated with higher prevalence of overweight mainly among girls, whereas playing digital games was not associated with overweight.

Taken together, these results emphasise the need to continuously monitor trends in overweight and obesity, as well as in the entire BMI distribution, and to study further the factors associated with these trends in adolescents as well as in children in order to develop appropriate health policy strategies for improving health and preventing obesity. The two concurrent findings, a decrease in the proportion of overweight and normal weight adolescents who perceive themselves as overweight and an increase in the prevalence of overweight, raise the question whether adolescents actually evaluate themselves more against their peers than against general cultural ideals. Further research is needed both to examine how the observed temporal changes in perceived weight affect adolescents well-being and behavioural choices and to assess the causality and mechanisms of the associations between time spent on specific forms of information and communication technology and overweight. As the different forms of information and communication technology keep widening, and changing in sedentariness, also their type and content will be of relevance in future studies.