joint strategic needs assessment foundation profile - JSNA

Interative Hull Atlas: www.hullpublichealth.org/Pages/hull_atlas.htm More information: www.jsnaonline.org and www.hullpublichealth.org
Interaction between two different factors can also occur which influence the relationship
with another factor. For example, there could be twice the risk of developing a disease
for a smoker compared to a non-smoker, and twice the risk of developing the same
disease if the person is overweight compared to someone who is within the „desirable‟
weight category, but for an overweight smoker the risk of developing the disease may be
ten times greater than a person who is a non-smoker and not overweight.
Therefore, examining the relationship between two factors is not straightforward. In
some cases, a relationship can seem to occur when there is no real relationship present
and it is just influenced by a confounding variable. In other cases, a relationship may
not seem to be present, but it is being masked by a confounder. Therefore, it is
important when assessing the relationship or association between two factors, to
consider potential confounding factors. In particular, as mentioned, age, gender and
different measures of deprivation are frequent confounders in relation to risk factors and
poor health.
12.3 Standardisation
The prevalence of ill-health, risk factors and disease and mortality within a particular
population will depend on the age and gender structure of that population (as well as
many other factors such as deprivation).
In terms of the provision of resources in relation to the prevalence of ill-health, disease
and risk factors in the population, it is most helpful to report on the prevalence without
taking into account the age and gender distribution of the population. This is because it
is necessary to treat and have the provision to treat the existing population, regardless
of the age and gender structure. However, if one wishes to assess whether one
population has an excess rate of disease or if there is a difference in the prevalence of
disease among different levels of deprivation, it is necessary to take the age and gender
structure into consideration. Otherwise any differences found may be simply due to
differences in the age and gender structure of the different populations, and not due to
the factor of interest, e.g. deprivation. The age and gender structure can be taken into
consideration by using standardisation. Generally, standardised rates are agestandardised
or age-gender-standardised, but rates can also be standardised to other
differences within the populations.
Direct standardisation involves applying the rates of disease (or prevalence of a risk
factor) observed in the study group of people to a „standard‟ population. Indirect
standardisation involves applying the rates of disease (or prevalence of a risk factor) in a
„standard‟ population to the study group of people. The rates or prevalence are
calculated for each gender and age group, for example, males aged 0-9, 10-19, 20-29
years etc and females aged 0-9, 10-19, 20-29 years etc. The standard population can
be an English population, the European Standard Population or a local population for a
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