Group Viljakainen

Finnish Health in Teens Study (Fin-HIT)

Fin-HIT- the Finnish Health in Teens Cohort - is a prospective cohort study including 11 500 Finnish adolescents (9-12 years of age at enrolment) and approximately 10 000 guardians. Fin-HIT studies prevalence, risk and protective factors associated with body size.

Fin-HIT was initiated to follow up body size development from early adolescence to adulthood. Our objective is to study how lifestyle, mental health, family, microbial, genetic and epigenetic factors interact in the development of body size and health outcomes over time. One of our overall study aims is to determine if the saliva microbiome is associated with body size and if so, can it be used for early detection of adolescents at risk of developing overweight and obesity. A deeper understanding of the association between microbiome and body size will pave the way for future studies such as intervention studies with probiotics, and its potential effect on the oral microbiota and body size development.

Baseline data collection was conducted by trained fieldworkers in schools during 2013-2014. Geographically, a large part of Finland is represented. 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 guardians answered a web questionnaire.

The first active follow-up with both adolescent and guardian was carried out during 2015-2016. The follow-up data consists of self-reported questionnaire and measurement data and saliva samples from both child and guardian. A follow up allows us to study changes in body size and health status in the participants over time, including microbiotic and epigenetic changes in body size development.

The collected research data will also be linked to national health registers which will provide more complete health profiles on participants. The registers include e.g. by the Population Register Cente, Social Insurance Institution of Finland (KELA), National Institute for Health and Welfare (THL) and Statistics Finland.

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Senior Scientists

Heli Viljakainen, PhD, Docent, Group Leader

Post-Doctoral Scientist

Elina Engberg, PhD

Graduate Students

Jannina Viljakainen, MSc

Sajan Raju, MSc

Sohvi Lommi, MSc


Catharina Sarkkola, MSc, Research Coordinator 

Figueiredo, R.A.O., Roos, E., Eriksson,J.G., Simola-Ström,S., Weiderpass, E. Maternal alcohol and tobacco consumption and the association with their 9 to 14-year-old children’s Body Mass Index Scandinavian Journal of Public Health 2017; 45: 503-510.

Rounge, T.B, Page C.M, 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

Sarkkola, C., Rounge, T.B., Simola-Ström, S., Von Kraemer, S., Roos, E., Weiderpass, E. Validity of home-measured height, weight and waist circumference among adolescents. Eur J Public Health 2016; 26 (6): 975-977.

Folkhälsan Research Foundation

Academy of Finland

Medicinska Understödsföreningen Liv och Hälsa 

The Swedish Cultural Foundation in Finland

Signe and Ane Gyllenberg Foundation

Yrjö Jahnsson Foundation

Päivikki and Sakari Sohlberg Foundation

Juho Vainio Foundation

Waldemar von Frenckells stiftelse

Ella ja Georg Ehrnroothin säätiö 

Institute for Molecular Medicine Finland, Helsinki

Institute for Molecular Medicine Finland FIMM Technology Center, Helsinki

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

CRIG group, Ghent university, Belgium

Department of Epidemiology, University of San Paolo, Brazil

THL Biobank

THL Public Health Promotion Unit 

University of Helsinki, Children’s Hospital


    • Heli Viljakainen

      PhD, Docent, Group Leader

    • Tel:
      +358 40 591 6998

    • Contact