Finnish Health in Teens Study

Fin-HIT – the Finnish Health in Teens – Study is a prospective cohort study including 11 400 Finnish adolescents (9–12 years of age at enrolment) and approximately 10 000 parents. Fin-HIT studies prevalence, risk and protective factors associated with weight status.

Fin-HIT was initiated to follow up weight development from early adolescence to adulthood. Our objective is to study how lifestyle, mental health, family, and microbial, genetic and epigenetic factors interact with the development of weight and health outcomes over time. One of our main topics is to determine if the saliva microbiome is associated with weight status and if so, can it be used for early detection of adolescents at risk of developing overweight and obesity. This has led us to explore the associations between microbiome and lifestyle factors, such as eating habits, antibiotics use and digital use, in order to deepen our knowledge on factors possibly shaping the saliva microbiome.

Baseline data collection was conducted during 2011-2014, mainly in schools by trained fieldworkers. Geographically, a large part of Finland is represented, focusing on densely populated areas. Children answered a questionnaire including questions on e.g. diet, physical activity, body image, sleep and screen time, had their weight, height and waist measured, and provided a saliva sample. The parents answered a web questionnaire.

The first active follow-up with both adolescents and parents was carried out during 2015–2016. The follow-up data consists of self-reported questionnaire, measurement data, and saliva samples from both children and parents. A follow-up allows us to study changes in weight and health, and related associations with microbial and epigenetic changes over time. A second follow-up with a web questionnaire has started in the autumn of 2020. The focus is on nutrition and mental health of the now young adult participants.

The collected research data have been linked to national health registers, which provides us comprehensive health profiles of the participants. The registers are maintained by the Digital and Population Data Services Agency, the Social Insurance Institution of Finland (Kela), the Finnish Institute for Health and Welfare (THL) and Statistics Finland. The saliva samples with selected research data are planned to be stored in the THL Biobank.

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Senior Scientists

Heli Viljakainen, PhD, Docent, Group Leader

Post-Doctoral Scientists

Nitin Agrawal, PhD
Marja Leppänen, PhD

Graduate Students

Sohvi Lommi, MSc
Laura Räisänen, MD


Catharina Sarkkola, MSc, Research Coordinator 
Binu Mathew, MSc, Bioinformatician, Data Manager

Lommi S, Engberg E, Tuorila H, Kolho K-L, Viljakainen H. Sex- and weight-specific changes in the frequency of sweet treat consumption during early adolescence: a longitudinal study. Brit J Nutr 2021, Mar 31;1-21.

Manzoor M, Lommi S, Furuholm J, Sarkkola C, Engberg E, Raju S, Viljakainen H. High abundance of sugar metabolisers in saliva of children with caries. Scientific Reports 2021, 11:4424.

Räisänen L, Viljakainen H, Sarkkola C, Kolho K-L. Perinatal risk factors for pediatric onset type 1 diabetes, autoimmune thyroiditis, juvenile idiopathic arthritis, and inflammatory bowel diseases. Eur J Pediatr (2021).

Raju S, Viljakainen H, Figueiredo RAO, Neuvonen PJ, Eriksson JG, Weiderpass E, Rounge TB. Antimicrobial drug use in the first decade of life influences saliva microbiota diversity and composition. Microbiome 8, 121 (2020).

Viljakainen J, Raju SC, Viljakainen H, Figueiredo RAO, Roos E, Weiderpass E, Rounge TB. Meal Regularity Plays a Role in Shaping the Saliva Microbiota. Front. Microbiol., 24 April 2020

Engberg E, Figueiredo RAO, Rounge TB, Weiderpass E, Viljakainen H. Heavy Screen Use on Weekends in Childhood Predicts Increased Body Mass Index in Adolescence: A Three-Year Follow-Up Study. J Adolesc Health. 2020 May;66(5):559-566.

Viljakainen H, Dahlström E, Figueiredo R, Sandholm N, Rounge TB, Weiderpass E. Genetic risk score predicts risk for overweight and obesity in Finnish preadolescents. Clinical Obesity 2019;e12342.

Figueiredo RAO, Simola-Ström S, Isomaa R, Weiderpass E. Body dissatisfaction and disordered eating symptoms in Finnish preadolescents. Eating Disorders. Jul 24:1-18.

Rounge TB, Page CM, Lepistö M, Ellonen P, Andreassen B, Weiderpass E. Genome-wide DNA methylation in saliva and body size of adolescent girls. Epigenomics 2016; Vol. 8, No. 11.

Folkhälsan Research Foundation

Academy of Finland

Medicinska Understödsföreningen Liv och Hälsa (“Life and Health Medical Fund”)

Signe and Ane Gyllenberg Foundation

The Swedish Cultural Foundation in Finland

Yrjö Jahnsson Foundation

Päivikki and Sakari Sohlberg Foundation

Juho Vainio Foundation

Waldemar von Frenckells stiftelse

Finnish Cultural Foundation

Minerva Foundation Institute for Medical Research

Institute for Molecular Medicine Finland, Helsinki

Finnish Institute for Health and Welfare (THL)

THL Biobank

Cancer Registry of Norway, Institute of Population-Based Cancer Research, Oslo, Norway

CRIG group, Ghent University, Belgium

University of Helsinki, Children’s Hospital

Panic Study, University of Eastern Finland

Department of Psychology and Logopedics, University of Helsinki

Department of Food and Nutrition, University of Helsinki

Institute of Clinical Medicine, University of Oslo


    • Heli Viljakainen

      PhD, Docent, Group Leader

    • Tel:
      +358 50 448 5660

    • Contact