Preventing cardiovascular disease

Preventing cardiovascular disease – analyses of cardiovascular outcomes and cardiovascular medicines use across DHBs and ethnic groups

The following analyses describe patterns in use by Māori of lipid-modifying agents (nearly all statins) to treat raised or deranged cholesterol levels, low dose aspirin to prevent thrombosisThrombosis is the formation of a blood clot (thrombus) inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot, because the first step in repairing it (hemostasis) is to prevent loss of blood. If that mechanism causes too much clotting, and the clot breaks free, an embolus is formed. (blood clots), ACE inhibitors for raised blood pressure and diabetesDiabetes is a syndrome of disordered metabolism, usually due to a combination of hereditary and environmental causes, resulting in abnormally high blood sugar levels (hyperglycemia). risk, and medicines to treat diabetes. These conditions are all import risk factors for cardiovascular diseaseCardiovascular disease refers to a class of diseases that involve the heart or blood vessels (arteries and veins). (heart attacks, strokeA stroke is the rapidly developing loss of brain function(s) due to disturbance in the blood supply to the brain. This can be due to ischemia (lack of blood supply) caused by thrombosis or embolism or due to a hemorrhage. As a result, the affected area of the brain is unable to function, leading to inability to move one or more limbs on one side of the body, inability to understand or formulate speech, or inability to see one side of the visual field. etc), which is leading cause of excess DALY loss by Māori (see above), and where cardiovascular medicines have the greatest gap between use and need by Māori (see above):

  • Cardiovascular disease (coronary heart disease and stroke) is still the number one cause of death in New Zealand and many of these deaths are premature and preventable .
  • Cardiovascular disease is a priority target in the New Zealand Health Strategy and PHARMAC’s Māori Responsiveness Strategy (2002) and Te Whaioranga- Action Plan (2007-2012).
  • Māori and Pacific men aged 35 years and older are the priority target audience because cardiovascular morbidity and mortality is higher and access to medicines poorer in this group than for other New Zealanders.

Analyses derive from recent in-house analysis performed or commissioned by PHARMAC staff, available on request from PHARMAC. Note that they describe comparative prescription levels only, with no adjustments for relative need.

The following analysis compares the Māori with the non-Māori non-Pacific-Island (nMnP) populations for the year financial year 2007/08.

Use of statins

The table below shows recent age-standardised rates of DHB statin prescribing during 2007/08 and relates those to disparities between Māori and Pacific usage and to cardiovascular outcomes. These help identify those DHBs whose statin use is lowest in relation to need (proxied by IHD mortality rates), and then where disparities for Māori and Pacific people are most for public health programmes. The table and the following graphs/narrative indicates:

  • lowest statin use overall, and in Māori vs. non-Māori, in Nelson Marlborough, South Canterbury
  • highest IHD death rates in Tairawhiti, Whanganui
  • highest IHD death rate in Māori relative to nonMāori in Tairawhiti, Capital and Coast, Northland
  • lowest RRs statin:IHD deaths (ie greatest unmet need overall) in Tairawhiti, Whanganui, Southland
  • highest inequalities deaths:statins Māori:nonMāori (ie greatest unmet need disparities for Māori) in Nelson Marlborough, MidCentral, Capital and Coast, Tairawhiti, Waikato.

Statin uptake by DHBs

Notes

  • Analysis is of direct age standardised rates of prescriptions rather than direct age standardised rates of dispensings, as dispensings may be dispensed stat (3-monthly) or monthly in different regions which would bias some estimates;
  • DHB is based on the domicile location of the patient rather than location of the pharmacy;
  • Death data are 5 year rolling averages;
  • Data are restricted to ages 35 years and over (previously IHD deaths had been standardised to the entire population); this is consistent with the prescribing guideline intent of the NZGG cardiovascular guidelines, with cardiovascular risk assessment broadly being recommended from age 35 years onwards.

2007/08 DHB rates versus the NZ Average for the year ending Jun 2008

This chart compares each DHB’s current age-standardised statin prescribing rates against the Māori and non-Māori non-Pacific (nMnP) average for the year ending June 2008.

In this chart the bottom left corner is least desirable while the top right corner shows higher prescribing rates for both Māori and nMnP and is most desirable. In the bottom left corner, prescribing rates for both Māori and nMnP in these DHBs are lower than the national averages for Māori and nMnP – being Nelson Marlborough, South Canterbury and Whanganui DHBs. In the top right corner, prescribing rates for both Māori and nMnP in these DHBs are higher than the national averages for Māori and nMnP – being Counties Manukau, Taranaki, and Hutt Valley DHBs.

The top left corner shows DHBs that had a higher prescribing rate for Māori compared to the Māori average and a lower prescribing rate for nMnP than the nMnP average i.e. more desirable for Māori but a lower than average prescribing rate for nMnP – being Wairarapa, Hawkes Bay and Northland DHBs. The opposite applies for the bottom right corner (more desirable for nMnP but a lower than average prescribing rate for Māori), having lower prescribing rates for Māori compared to the Māori average and higher prescribing rates for nMnP than the nMnP average) – being Otago DHB.

Statin usage versus IHD mortality

In this graph, values to the left of the diagonal line show lower statin prescribing than expected from age-standardised IHD deaths (e.g. Whanganui, Midcentral DHBs), while to the right of the diagonal line show higher age-standardised statin prescribing versus IHD deaths (e.g. Counties Manukau).

Values above the horizontal line show higher age-standardised statin prescribing compared with the NZ average (e.g. Counties Manukau), while below the line show lower age-standardised statin prescribing than the NZ average (e.g. Midcentral).

Values to the right of the vertical line show higher age-standardised IHD deaths than the NZ average (e.g. Tairawhiti), while to the left is lower age-standardised IHD deaths than the NZ average (e.g. South Canterbury).

Assuming (unrealistically) all things else being equal (i.e. other risk factors such as tobacco use, raised blood pressure were distributed equally by ethnicity and DHB), then Whanganui and Midcentral DHBs therefore show the greatest disparities between statin prescribing and IHD rates.