Physical activity levels in public school teachers

MÉTODOS: Estudo transversal conduzido com 1.681 professores de São Paulo, SP, em 2009. A versão curta do Questionário Internacional de Atividade Física foi aplicada e o nível de atividade física dos professores foi categorizado em baixo, moderado ou alto. A amostra foi estratifi cada por idade, região da cidade e sexo. O teste de qui-quadrado foi aplicado nas comparações e o nível de signifi cância adotado foi de p < 0,05.


INTRODUCTION
Low physical activity level (PAL) is a major risk factor for development of chronic degenerative diseases such as heart diseases, cancer, hypertension, diabetes and obesity. 17,a Epidemiological studies have shown high rates of physical inactivity world. In Finland, for example, this rate is as high as 71%, outweighing other major risk factors such as smoking, hypercholesterolemia, arterial hypertension and obesity. 18 Low PAL is also extremely high (greater than 60%) in countries like the United States, Australia and England. 7 Monteiro et al 12  In addition to the impact of a sedentary lifestyle to people's health, inadequate levels of physical activity are also associated with considerable economic costs for governments. 1 Having a physically active lifestyle entails health promotion and improved quality of life and may be a sound investment in public health. 3,10,11,18 Data available show the need for ongoing monitoring of PAL in the population, which basically rely on effective public health programs to encourage a physically active life. There are scarce studies on PAL among teachers but they are necessary to characterize this risk factor. This study aimed to assess PAL in public school teachers.

METHODS
A retrospective study with a sample of 1,681 teachers from state public schools in the city of São Paulo was carried out in 2009. This study was part of an institutional assessment in 2009. At that time, there were 257,464 teachers distributed in 91 regional school districts statewide. Of these, 48,785 served 13 school districts in the capital São Paulo. c A communication detailing the proposed research project was sent to all school districts in the capital for consideration and approval. Following consultation, two school districts and their related schools agreed to participate in the research study. The study was conducted in 40 randomly selected schools in the east (eastern regional district 1) and 40 in the south area of the city (southern-central regional district).
The study was conducted between November and December 2009. In addition, data here presented are part of another study aimed to assess the association between different PALs and excess body mass.
For estimation of the adequate sample size the following equation was applied: 15 N = (z 2 .p.q)e 2 , where z is the 95% confi dence interval (95%CI), p is the proportion of occurrence of the event; q is the proportion of non-occurrence of the event (100-p); and e is the maximum error allowed (2.5%). P-values were derived from previously published estimates. 7 The following correction equation was applied: N = n 0 / (1 + n 0 / n), where n 0 is the initial sample size; and n is the size of the study population (48,785 teachers).
Inclusion criteria included being a public school teacher; not in sick leave; and having permanent residence in the city area of the school district. Not being a practicing teacher was an exclusion criterion. A total of 1,713 teachers met the inclusion criteria. Of these, 32 were excluded because of missing information on PAL. The fi nal sample comprised 1,681 teachers.
The International Physical Activity Questionnaire (IPAQ) version 8, validated for the Brazilian population, was used to estimate PAL. 9 Teachers were interviewed using IPAQ short form. The questions were asked regarding the preceding week, exploring the frequency and duration of physical activity (PA) including walking and moderate and vigorous physical exercise. PAL was classifi ed into three levels: d

RESULTS
The overall mean age was 40 years (range: 19 to 66). Table 1 shows the general characteristics of the sample studied.
Teachers mostly had low PAL and a small proportion had PALs. There was a median prevalence of moderate PAL in the sample (Figure).
Most teachers with low PALs were 31 to 54 years of age. There was a lower prevalence of low PAL among those aged 55 to 66 years compared to those aged 19 to 36. The same was seen for moderate and high PALs ( Table 2).
The proportion of low and high PAL among teachers was higher in the eastern area of the city and the proportion of moderate PAL was higher in the southern area (Table 2).
Low and high PAL was higher among men than women.
The contingency analysis showed a signifi cantly lower proportion of moderate PAL among men than women ( Table 2).    16,a The positive association between low PAL and aging is strongly supported by literature. 4,6 In our study it was verifi ed only in individuals younger than 54 and the prevalence of low PALs reduced with age (55 to 66 years). It is possible that low PALs throughout life may be associated with the development of chronic degenerative diseases, reduced performance status and lower quality of life. 2,5,a This can be particularly valid for teachers aged 55 to 66 years as they showed reduced prevalence of moderate and high PA ( Table 2).

DISCUSSION
PAL among teachers may vary by city area. There was seen a greater proportion of teachers low and high PAL in the eastern than in the southern area of the city, and moderate PAL was signifi cantly lower in the eastern area. These fi ndings may encourage the formulation of public policies aimed to reduce low PALs in areas of the city that require more attention.
Moderate PAL was signifi cantly more prevalent among women than men. However, the prevalence of teachers with low and high PAL was greater in men. Household physical activity is included in the assessment of PAL with IPAQ and may be refl ected in the greater proportion of moderately active teachers found in our study since household chores are mainly done by women. 8 The fi nding of a greater proportion of high PAL among men can be attributed to a greater amount of time spent on occupational PA and sports. 7 The present study evaluated only public school teachers in eastern and southern areas of the capital, making the results not fully representative to the entire city of São Paulo. There is a need to assess the segments of the school system in other areas (north and west) that were not evaluated. However, the results of this study constitute a fi rst step for further research in areas of the city with specifi c social and environment characteristics associated with different PALs.
In conclusion, a signifi cant number of teachers have low PALs, which may vary according to age, gender and city area. Public and private authorities can use the study data to support the planning of actions targeted to public school teachers in the state of São Paulo and ensure greater involvement and promotion of PA.