Cancer and inequality

Key points

• Differences in the health of demographic groups result from living habits, exposure to environmental risk factors, seeking and receiving treatment, the treatment itself and healing after treatment.
• The risk of falling ill with cancer varies amongst demographic groups. The risk of e.g. colon and breast cancer is greater within higher social groups. The risk of esophageal, stomach and pancreatic cancer is increased amongst lower social groups.
• Social groups also have an impact on survival rates.
• To decrease differences in health, more specific data regarding reasons behind the differences is needed.

No-one can influence what kind of family and environment they are born into. A child’s home and its values and habits form a foundation for later life and career choices. Influences from early education and school environments, as well as opportunities for hobbies also have an effect. Physical and cultural living environments also in part define conditions and individual choices. An individual’s place of residence is also connected to the quality and availability of health services as public healthcare in Finland is based on the municipality one resides in.

There are wide variations in morbidity and mortality between demographic groups in Finland and other countries as well. The differences result from diverse living habits, exposure to environmental risk factors, seeking and receiving treatment, the treatment itself and healing after treatment.

Differences can be considered socially discriminating when they do not origin from conscious and deliberate choices by individuals. The majority of differences based on social status and residence can therefore be considered discriminating and the factors behind them should be removed or their impact should be reduced. [1]

_{Figure 1. Age- ja sex-standardised five-year cancer-specific survival proportions (%) for patients diagnosed in Finland in 1996-2005 by educational level (high, secondary, basic). (Pokhrel et al. 2010).}

Definition of social status

According to the National Institute for Health and Welfare (THL) the most important factors affecting social i.e. socio-economic status are education, labor market status, social class based on occupation and income and wealth. They are interlinked, but also portray the various dimensions of social status. [2]

Education is usually obtained in one’s youth or as a young adult. Education acquired at a later age only rarely changes the individual’s highest level of education. Education impacts labor market and professional status, which according to THL attach the individual to essential structures of society defined by employment. In turn, labor market and professional status define earnings and financial status. Social recognition and influencing opportunities, for example, are also connected to social status.

The three most commonly used indicators of social status in cancer epidemiological research are: level of education, social class determined by profession (I-IV) and annual income. [3] The two first especially are of particular interest while looking at cancer risk factors, as they are highly correlated with lifestyle. When examined the survival rates of cancer patients, labor market status is also an important indicator.

The study of connections between social status and cancer has been somewhat challenging especially when looking at previous decades due to the different labor market positions of men and women as well as their different roles in households.

Social status and the risk of cancer

According to the World Health Organization’s (WHO) International Agency for Research on Cancer (IARC), approximately half of cancer cases could be prevented, and according to Cancer Research UK approximately 40% of cancers are due to living habits.

In Finland and other Western countries unhealthy lifestyle choices are, as a rule, more common in lower social groups. Particularly important risk factors include smoking, alcohol consumption, unhealthy diet and immobility. In addition to cancer, these are also the most important causes of many other common diseases: cardiovascular diseases, diabetes and respiratory tract obstructive pulmonary disease. For example, in Finland smoking is estimated to explain almost 17-20% of mortality of men over the age of 50, and 4-10% of women of the same age. [4]

The influence of social status on morbidity

The risk of developing cancer varies by social group, but the relation of the social status to the risk is diverse for different cancers. According to a longitudinal study conducted in Finland the risk of developing e.g. colon cancer and breast cancer in women was higher within the upper social groups during 1971-1995. Results with esophageal, gastric and pancreatic cancer were opposite. [5]

In the past, exposure to cancer risk factors in the work environment increased the differences of cancer between social classes. At present, the impact of the work environment is less relevant and often indirect. For example, in certain occupations, smoking is still common, such as in restaurant work and construction work.

An extensive Nordic follow-up-study found significant differences in cancer risks between occupational groups. The researchers concluded that social factors related to professions are more important for some types of cancer risk factors than the actual factors associated with professions. [6]

The influence of social status on mortality

One way to examine the impact of social status on mortality is to approximate how much the mortality rate would be reduced if everyone had the same survival rates as the social group that has the best survival rates. A study based on cancer registry data found that nearly 3% of cancer deaths could have been avoided during the years 2008-2012. Endometrial cancer, cervical cancer and skin melanoma as much as over ten percent of cancer deaths could have been avoided. [7] Figure 1 illustrates age- ja sex-standardised five-year cancer-specific survival proportions (%) for patients diagnosed in Finland in 1996-2005 by educational level (high, secondary, basic).

There are differences between the social groups in the survival rates of nearly all cancers. If differences occur, survival rates are better amongst the more educated. Some of these differences can be explained by the fact that with the less educated people there has been more time for the cancer to already spread in the nearby tissues or send metastases further than with more educated people. Other studies confirm that with members of the lower social groups a cancerous tumor is less often locally limited. This would suggest that patients in lower social classes seek treatment or are sent for further examination later than more prosperous individuals. [1, 3]

Also, deaths due to other reasons explain survival rates between the groups. These are linked mainly to differences related to smoking, alcohol consumption and diet.

One important factor for mortality differences between social groups is smoking and drinking, which are more common in the lower social classes. Alcohol and smoking-related deaths are estimated to shorten the expected life span of men by 4-5 years, and women by 1.2 years. [8, 9] Differences in mortality between population groups have grown, but the importance of differences in men’s smoking has constantly decreased as a factor. Women’s smoking in turn explains health differences more clearly than before. [10]

Reducing disparities between population groups

Reducing discriminating social and regional disparities has been one of the main objectives of Finnish health policy for decades. However, differences have continued to increase despite the government’s efforts.

Decreasing health inequalities requires more detailed understanding of underlying reasons. Improving the availability and quality of health services throughout the country is a necessity, but on the other hand, an insufficient means alone. There is a need to raise public awareness of the risk factors, healthy lifestyle choices and early symptoms of cancers. Public authorities must on their own behalf help to ensure that citizens’ exposure to carcinogenic agents is determinedly decreased.

Literature

1. Karjalainen S. Equity and cancer patient survival. Thesis. Acta Universitatis Tamperensis ser A vol 316. Tampere: University of Tampere 1991.
2. National Institute for Health and Welfare. Eriarvoisuus. Published online 10.5.2016. https://www.thl.fi/fi/web/hyvinvointi-ja-terveyserot/eriarvoisuus.
3. Auvinen A, Karjalainen S, Pukkala E. Social class and cancer patient survival in Finland. Am J Epidemiol 1995; 142: 1089–102.
4. Martikainen P, Ho J, Preston S, Elo I. The changing contribution of smoking to educational differences in life expectancy: indirect estimates for Finnish men and women from 1971 to 2010. J Epidemiol Community Health 2013; 67: 219–24.
5. Weiderpass E, Pukkala E. Time trends in socioeconomic differences in incidence rates of cancers of gastro-intestinal tract in Finland. BMC Gastroenterol 2006; 6: 41.
6. Dickman P, Gibberd RR, Hakulinen T. Estimating potential savings in cancer deaths by eliminating regional and social class variation in cancer survival in the Nordic countries. J Epidemiol Comm Health 1997; 51: 289–98.
7. Pukkala E, Martinsen JI, Lynge E et al. Occupation and cancer – follow-up of 15 million people in five Nordic countries. Acta Oncol 2009; 48: 646–790.
8. Pokhrel A, Martikainen P, Pukkala E, Rautalahti M, Seppä K, Hakulinen T. Education, survival and avoidable deaths in cancer patients in Finland. Br J Cancer 2010; 103: 1109–14.
9. Martikainen P, Makela P, Peltonen R, Myrskylä M. Income differences in life expectancy. The changing contribution of harmful consumption of alcohol and smoking. Epidemiology 2014: 25: 182–90.
10. van Raalte A, Myrskylä M, Martikainen P. The role of smoking on mortality compression: An analysis of Finnish occupational social classes, 1971−2010. Demographic Research 2015; 32: 589–620.