Mid-upper arm circumference and body mass index as different screening tools of nutritional and weight status in Polish schoolchildren across socio-political changes.

Intergenerational changes in many biological traits are indicators of environmental conditions. One of such anthropometric measures is the mid-upper arm circumference (MUAC) which estimates nutritional status. Likewise, Body Mass Index (BMI) is widely used as an anthropometric indicator of relative weight. The aim of this study was to reveal secular trends in MUAC and BMI, as biological indicators of changing living conditions, between 1966 and 2012 among Polish children from different socioeconomic groups. Total sample involved 64 393 schoolchildren aged 7-18 years, investigated in 4 Surveys (1966, 1978, 1988, 2012). Overall socioeconomic status (SES) was divided into two categories: lower and higher (including: urbanization, family size, parental education). Results showed that MUAC and BMI differed significantly with respect to the year of survey, sex and SES category. Both measures were higher within higher SES group compared to the lower one until 1988, while in 2012 convergence of these indicators in both SES categories was observed. Both the year of survey, sex, SES category and interactions between them had higher impact on MUAC than BMI (measured by effect size). Our findings revealed that long-term socioeconomic changes affect MUAC more noticeably than BMI. Therefore MUAC may be a more accurate screening tool.