Comparing the utility of the Theory of Planned Behaviour and the Health Belief Model in understanding and promoting the use of protective helmets among school-age cyclists

The thesis set out to compare the Health Belief Model (Rosenstock, 1966, 1974) and the Theory of Planned Behaviour (Ajzenm 1985,1991) in terms of their usefulness in understanding and predicting health behaviour and their ability to guide the construction of effective behaviour change interventions. The models were used to investigate the beliefs associated with the use of protective helmets amongst school-age cyclists in order to design and evaluate an intervention aimed at promoting the use of helmets by students while cycling to and from school. To aid comparison, the Health Belief Model (HBM) included a meausre of behavioural intention mediating between beliefs and behavour.

In the first of two prospective studies, the models successfully predicted helmet use amongst a sample of teenager boys while cycling to and from school and identified beliefs discriminating between helmet users and non-users. A second longitudinal study limited the influence of past behaviour by predicting helmet use among secondary school girls and boys from beliefs assessed at junior school before they began cycling to and from school. These studies confirmed the predictive utility of the models and showed the Theory of Planned Behaviour (TPB) superior to the HBM in terms of predictive power, conceptual strengths and sufficiency. The third study used the beliefs identified as most salient by the TPB to inform a persuasive intervention based upon the Elaboration Likelihood Model of Persuasion (Petty and Cacioppo, 1986), intended to promoted the use of helmets. A series of persuasive messages, presented to non-helmeted cyclists, suceeded in promoting positive beliefs and intentions vis a vis helmet use while cycling to and from school and brought about a 25% increase in helmet use. Both effects were sustained over time. This programme of research confirmed the explanatory power of the TPB for predicting health behaviour.