Van Gool & Bridges
4 COST-EFFECTIVENESS ANALYSIS
Effectiveness
Length OfEffectiveness for Interventions
Several studies note the importance of the length of the intervention. For example,
Loughlan and Mutrie (1997), in their evaluation of three exercise interventions, state
that ongoing support is required to maintain initial gains. Van Beurden et al (1993) in
their evaluation of the North Coast Cholesterol Check campaign supports this view.
For evaluation purposes it is also important to provide sufficient time for an intervention
to take full effect. Tones (1994) and Engleman and Forbes (1986), both support the
view that a long follow-up period is required before the intervention can have an impact
on mortality and morbidity.
For the purposes of this analysis it was assumed that the program would be run over a
one-year period. However, the benefits of the intervention would flow to the
community for a number of years. In other words, the gains of the program are
cumulative over the period of effectiveness.
It is also assumed that a one-year program will not have a permanent affect on people’s
behaviour. This means that a program will have a limited time span. In this analysis
the time span varies for each intervention. The implication of this is that by the end of
the period of effectiveness, people will have reverted back to their previous behaviours
and risk factors.
As the period of effectiveness varies for each intervention, for the purposes of this
study, a lower and upper bound for effectiveness has been identified and the mid-point
has been used to calculate the cost-effectiveness of each intervention.
The length of effectiveness for each intervention has been based on consultations with
people in the SWSAHS at a workshop held in July 1998 as well as discussions with
staff. The lower and upper bounds, as well as the midpoints, are presented in table 4.
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Chere Project Report 11- November 1999