Prior to our period of analysis, the years from 1950 to 1970 saw a dramatic development with mortality from ischemic heart diseases nearly doubling for the 40 – 69 age group (5). The positive trend in recent decades is no less dramatic, with a formidable reduction in myocardial infarction mortality. In recent years mortality for the under 80s has remained at only 20 – 30 % of its level at the beginning of the 1970s. This is a gratifying development which has exceeded all expectations. The findings are in keeping with our recently published analyses, which indicate that the incidence of myocardial infarction has also fallen considerably in the 1990s and 2000s (3). With mortality rates showing a downward trend also for the oldest group, it is clear that the favourable development has taken place in all age groups.
The reasons for the time lag – that the strong decline in mortality began first among the youngest group and last in the oldest group – may be that a more favourable risk profile, better medication and a more effective invasive treatment strategy first had an impact on the youngest age groups. An improved and swifter response among the youngest groups may well be related to a lesser degree of subclinical atherosclerosis in the coronary arteries. If the disease process has not started in the vessel wall, an improved profile of the modifiable risk factors might provide a better effect. The deferral of myocardial infarction to a higher age is part of the successful campaign against cardiovascular diseases (1, 2) and may have contributed to the age gradient. It is also likely that improved medication and invasive treatment was offered to younger age groups first, which may have led to a reduction of mortality in these groups first. We observed an earlier and more extensive use of percutaneous coronary intervention (PCI) in the younger groups (data not shown).
Moreover, there are complex reasons for the lower incidence of coronary heart disease in Western countries. An American study attempted to estimate the contribution of various input factors and concluded that a more favourable risk profile and improved treatment had both played an almost equally important role (6). The findings of a Swedish study showed that just over half the reduction in mortality from 1986 to 2002 could be attributed to a more favourable profile for the classic risk factors and approximately one-third was due to improved individual treatment (7). In the period from 1972 to 2007, Finland reported an 80 % decline in mortality from coronary heart disease in males aged 25 – 74, and the change in risk factors – cholesterol level, blood pressure and smoking – could explain a 60 % decline in mortality (8).
How does myocardial infarction mortality in Norway compare with other countries? Norway has long been classified as a high-risk country but the decline in mortality around 2000 placed the country on approximately the same level as Greece and not far behind the Mediterranean countries of France, Italy and Spain, which are the countries with the lowest mortality from cardiovascular diseases (9). In Denmark and Sweden the development has been almost the same as in Norway while Finland, where there was initially a very high level of myocardial infarction, continued to have somewhat higher mortality rates than neighbouring countries in 2000 (9, 10). It will be exciting to see whether comparisons for recent years show a further decline in the differences.
In Europe, tables based on the American Framingham Heart Study (11) were used previously for the estimation of individual risk, but over time these were deemed to be less suited. Instead so-called SCORE-tables were introduced in 2003 (12). Norwegian data material constitutes part of the database for the SCORE tables that are applicable to the high-risk countries among which Norway has always been classified. However, the Norwegian patient data included in the SCORE project were collected several decades ago, and in recent years it has been suggested that they overestimate cardiovascular mortality and are thus less applicable (13). A new system, the NORRISK-model, has been introduced and is proposed as an improved tool in risk evaluation (14).
Our results concern myocardial infarction mortality but in some contexts it is of interest to examine statistics for the entire cardiovascular field. Myocardial infarction constitutes the largest group, but over the last decades mortality from cerebral stroke – the next largest group – has also diminished considerably (9, 15).
Overall we have witnessed a surprisingly positive trend in Norway. However, there is no reason to rest on our laurels. This trend might be reversed, particularly because there is considerable uncertainty regarding how the «epidemic» of inactivity/obesity will affect mortality rates from a long-term perspective. All-out efforts to combat cardiovascular diseases are still essential.