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Are health effects of cycling underestimated due to inaccurate estimates of the physical activity?

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This is the accepted version of a paper presented at The 10th HEPA Europé Conference on Health Enhancing Physical Activity, University of Southern Denmark, Odense, Denmark, August 28-30, 2019.

Citation for the original published paper: Schantz, P. (2019)

Are health effects of cycling underestimated due to inaccurate estimates of the physical activity?

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N.B. When citing this work, cite the original published paper.

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Are health effects of cycling underestimated due to inaccurate estimates of the

physical activity?

Peter Schantz

dr med sc, professor

Research Unit for Movement, Health and Environment The Swedish School for Sport and Health Sciences GIH, Stockholm, Sweden, www.gih.se/mhe

This is a summary of my perspectives as Discussant at the symposium: “Cycling and health in Europe and beyond – explaining and updating the evidence base” at the 10th HEPA Europe Health Enhancing Physical Activity Europe Conference at Southern University of Denmark in Odense, Denmark, August 28-30, 2019. Contributors to the symposium were Drs Adrian Bauman, Sylvia Titze, Niamph Murphy and Pekka Oja.

I decided to focus on the part of the symposium dealing with health effects. The size of them is not only of academic interest, but may affect traffic planning and thereby have substantial effects on how cities are planned. This is since in many countries, investments in the transport sector are dependent on cost-benefit analyses, and various investment alternatives are most often weighed against each other. This is also the reason for the development of the WHO Health Economic Assessment Tool for cycling and walking.

At the symposium, the current state of knowledge was well described in this respect. So my contribution was instead to describe the risk for that the evaluations undertaken so far are more or less hampered by poor input data in relation to the true levels of physical activity attained from cycling. The effect of that is in such case that the estimates of health effects will be too low. This principal effect was illustrated with data from a study by Ekblom et al. (2015) on self-reported versus accelerometry-based levels of sitting time (Figure 1).

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It was then further illustrated with objectively and subjectively based studies of the risk for premature mortality with sitting time as summarized på Chau et al. (2013)(Figure 2). Clear differences in the relations were illustrated.

Figure 2. The study with diverging findings in the relation of hours sitting and mortality rate is based on accelerometry measures, whereas the other studies are based on self-reported data.

Thereafter, the same phenomenon as in Figure 1 was illustrated with self-reported vs accelerometry-based levels of physical activity (Ekblom et al. 2015)(Figure 3).

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Then the relation between self-reported leisure-time versus objectively measured physical activity and all-cause mortality was shown with data from Paffenbarger et al. (1986) and Manini et al. (2006). Again, clear differences in the relations were illustrated, with greater effects with the objective methods.

All forms of physical activity can be evaluated on the basis of: frequency x duration x intensity. I have, however, not seen any published data with validated methods establishing these three constituents for transport cycling. This is reason enough to doubt that there the currently used effect sizes related to cycling and health are adequate.

Neither have I seen any reproducibility studies of these variables. But I have, through several studies realized that it is, or may likely be, rather or very difficult to measure these matters correctly. For example there is, or may be, a great variability over the year in frequency of cycling trips (Stigell & Schantz 2015)(Figure 4).

Figure 4.

Furthermore, self-reported durations may include various number of resting periods because of red lights or other stops, and systematic errors appear to be coupled to duration reports using the last digits 0 and 5 in minutes of cycling reported (Schantz 2017). Finally, intensities of cycling, as mirrored in estimated cycling velocities, vary greatly (Schantz 2017), which means that it is difficult to specify in MET-values and MET-hours per week, etc. for the cyclists (Figure 5).

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4 Figure 5.

As a consequence of this information it is very difficult to establish a valid or even near valid measure of the physical activity in transport cycling, at least if we are interested in greater groups of individuals needed for epidemiological studies. I therefore argued during the symposium that it is inevitable that epidemiological studies of health effects of cycling up to this date, which are all based on self-reports, underscore the magnitude of the health effects.

To develop the understanding of cycling and health there is therefore a strong need for methodological studies and development. When refined methods exist there is indeed a great need for a second generation of epidemiological studies in this important field of science.

References

Chau JY, Grunseit AC, Chey T, Stamatakis E, Brown WJ, Matthews CE, Bauman AE, van der Ploeg HP. 2013. Daily sitting time and all-cause mortality: a meta-analysis. PLoS One 8(11)

Ekblom Ö, Ekblom-Bak E, Bolam KA, Ekblom B, Schmidt C, Söderberg S, Bergström G, Börjesson M. 2015. Concurrent and predictive validity of physical activity measurement items commonly used in clinical settings--data from SCAPIS pilot study.

BMC Public Health 15:978.

Manini TM, Everhart JE, Patel KV, Schoeller DA, Colbert LH, Visser M, Tylavsky F, Bauer DC, Goodpaster BH, Harris TB. 2006. Daily activity energy expenditure and mortality among older adults. JAMA 296(2):171-9.

Paffenbarger RS Jr, Hyde RT, Wing AL, Hsieh CC. 1986. Physical activity, all-cause mortality, and longevity of college alumni.

N Engl J Med. 6;314(10):605-13.

Schantz, P. 2017. Distance, duration and velocity in cycle commuting – analyses of relations and determinants of velocity. Int

J Environ Res Public Health 14 (10)

Stigell, E. & Schantz, P. 2015. Active Commuting Behaviours in a Nordic Metropolitan Setting in Relation to Modality, Gender, and Health Recommendations. Int J Environ Res Public Health 12 (12):15626-48

References

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