Health Inequities in Manitoba: Is the Socioeconomic Gap

Health Inequities in Manitoba: Is the Socioeconomic Gap in Health Widening or Narrowing Over Time?
Ischemic Heart Disease (IHD)
Ischemia is a condition in which the blood flow (and thus oxygen) is restricted to a part of the body.
Cardiac ischemia is the name for lack of blood flow and oxygen to the heart muscle. Thus, the term
‘ischemic heart disease’ refers to heart problems caused by narrowed heart arteries. When arteries are
narrowed, less blood and oxygen reaches the heart muscle. This is also called coronary artery disease
and coronary heart disease. It can ultimately lead to heart attack.
In this study, the crude and adjusted prevalence of IHD was measured for residents aged 19 and older
over eight 3-year periods. Residents were considered to have IHD if they met one of the following
conditions:
• one or more hospitalizations with a diagnosis of IHD: ICD–9–CM codes 410–414; ICD–10–CA codes
I20–I22, I24, I25
• two or more physician visits with a diagnosis of IHD (ICD–9–CM codes as above)
The denominator includes all Manitoba residents aged 19 and older in the specified time period.
Lorenz Curve
In this study, the Lorenz curve is a graphical display of the distribution of the cumulative percent
of events by the cumulative percent of people in the five neighbourhood income quintiles in the
population, by increasing income. The horizontal axis (x–axis) of the curve displays the cumulative
percent of people in the population (by increasing neighbourhood income quintile group) and the
vertical axis (y–axis) displays the cumulative percent of events in the population. The Lorenz curve can
be expressed as what percentage of the population represented by the neighbourhood income quintile
holds what percentage of the events in the population. Each neighbourhood income quintile represents
approximately 20% of the Manitoba population, divided into rural or urban (Winnipeg and Brandon).
In a perfectly equitable situation, one would expect that 20% of events (i.e., premature deaths, teenage
pregnancies, etc.) would occur in each income quintile group: U1 would contribute 20% of all events
in the population; U2 would contribute another 20% of all events in the population and so forth. As a
reference, a line of equality is also displayed on the graph to indicate this perfectly equitable situation;
however, most cases present some inequality between the percentage of events and the income
quintiles of the population. A Lorenz curve is generated when at least one of the income quintiles that
captures N% of the population does not contribute the same N% on the Y axis. If a larger proportion of
events occur in lower neighbourhood income quintile groups, the Lorenz curve will bend above the line
of equality; if a larger proportion of events occur in higher neighbourhood income quintile groups, the
Lorenz curve will bend below the line of equality (Lorenz, 1905).
The total area lying in–between the line of equality and the Lorenz curve is known as the GINI
coefficient; larger areas represent larger disparities between neighbourhood income groups and
smaller areas represent smaller disparities between neighbourhood income groups. Please see Gini
coefficient for more information.
On the next page is an example of a Lorenz curve. Here we see that U1 (lowest urban neighbourhood
income quintile representing 19.5% of the population) accounts for 33.4% of all premature deaths.
Manitoba Centre for Health Policy 201