Why do health behaviours change over time?  When we discuss how common a problem is, we refer to its prevalence. Prevalence signifies what proportion of a certain population engages in a certain behavior. As speaking about prevalence generally would be too broad of a topic, we will concentrate on the prevalence of smoking and obesity because both are commonly studied health problems. For instance, current prevalence of smoking in the United States of America is 15.1% while for obesity it is 36.5% (CDC, 2016). However, prevalence is not a stable variable; it changes over time and there are various factors which influence it. We will concentrate on these factors in this chapter.

The prevalence of smoking

In 1921 German scientists were the first to link smoking to lung cancer which led to anti-smoking propaganda by the Nazis during the Second World War, together with the fact that Hitler regarded smoking as a waste of money. After the war though, people returned to smoking especially in the fifties and at the beginning of the sixties; this may have been caused by the intense marketing campaigns of tobacco-producing companies. Cigarette brands sponsored television shows, included film stars, singers, and even athletes in their campaigns, and produced catchy slogans and colorful adverts. Additionally, they often targeted youth as a part of their marketing.

In 1954, a study in the United Kingdom linked smoking to lung cancer again and this became accepted by 1964 in the USA as well. By the 1980s, much evidence had been gathered on the health risks of smoking and consequently, the prevalence of smoking began declining in many countries. Many countries also began implementing anti-smoking policies such as restricting certain types of advertisements, prohibiting smoking in certain environments, additional taxation, and requiring proof of age when buying cigarettes. As a result of all these factors, smoking prevalence in the United States, for example, decreased from 42% in 1965 to the current 15.1%. Therefore, there is evidence that education and legislation were two of the most impactful factors regarding smoking prevalence over the past century.

Furthermore, anti-smoking media campaigns can also be successful in reducing the number of smokers. The Centers for Disease Control and Prevention, the official government health agency in the United States, launched the anti-smoking campaign Tips from Former Smokers in 2012 and the results in 2017 show that between 2012 and 2015 around half a million smokers quit the habit - and many more attempted to do so. It also stirred a public debate on smoking even amongst non-smokers (CDC, 2017).

Research in smoking prevalence

Feigl et al (2015) conducted a study to determine whether a school smoking ban in Chile had any effect on teenage smoking prevalence. The ban included schools as smoke-free zones and also implemented a cigarette sale ban in an area of 300 meters around schools. This law went into effect in 2006. The authors collected their data from 2001 to 2011 by carrying out countrywide surveys of high school students, ages 14 - 18 years old.  The surveys were conducted every odd year, therefore there were six surveys in total. As a control group, the researchers reviewed general population surveys for the 19 - 24-year-old age group. Their sample included 319 798 individuals.

The results were that smoking prevalence among Chilean teenagers was rising between the years 2001 and 2005; however, once the ban came into effect, the prevalence of teenage smoking decreased. In 2001, 41.9% of high school students had some experience with smoking while in 2011 it was only 25.7%. In the control group, 57.3% smoked in 2003 and 44.9% smoked in 2011. There was a more significant decline in smoking in the target group compared to the control group.

However, looking a bit more closely at the statistics raises some questions.  The data is the prevalence of the whole sample.  When divided by grade level, the researchers found that the decline was apparent only in the lower school grades; the ban had no apparent effect on the higher grades. Furthermore, the ban had an effect on the number of smokers but not the number of cigarettes smoked per day by each smoker. Although the ban may have slowed the initiation of smoking behaviour, it may not have had much effect on students who were already smoking. The study lacks depth of information because the researchers had no contact with the subjects of the study.

Another study on smoking was carried out by Evans, Farrelly, and Montgomery (1999).  The researchers investigated the effect of smoking bans in the workplace on smoking prevalence. The researchers used data retrieved from NHIS (national health interview survey) from two years – 1991 and 1993. These surveys asked not only about smoking habits but also about smoking policies in the workplace. Altogether, the sample constituted of 18 090 subjects and was nationally representative. The researchers found that in this timeframe smoking decreased by 5-7% and the average cigarette consumption per smoker declined by 2.3 cigarettes a day. The researchers concluded that the difference in smoking cessation could be attributed to workplace smoking bans. However, there are many personal factors that motivate an individual to quit smoking that are not accounted for in this study. 

Prevalence of obesity

The current prevalence of obesity (2016) in the United States of America is 36.5%, which is over a third of the population. Historically, this was not always the case. Throughout most of history, obesity all around the world was rare and manifested exclusively among the highest strata of the society as the majority of the population struggled to get enough to eat. During medieval times, obesity was seen as a sign of wealth and was socially valued.

Yet after the industrial revolution, when production became mechanized, work became more sedentary and society richer; obesity rates started to grow.

Today, obesity is no longer seen as a sign of prosperity but rather as a disadvantage and even as a personal flaw. Still, obesity rates continue to grow in most western countries and in 2014, around 600 million individuals (13% of the population) were obese according to World Health Organization (2017). This is most likely caused by the frequent consumption of calorie-dense foods and a decrease in regular exercise due to urbanization, ways of transport, and the nature of work (WHO, 2017).

Research in obesity prevalence

She, King, and Jacobson (2017) published a study that concentrated on the relationship between public transport use and obesity. The authors gathered data on obesity from CDC’s Behavioral Risk Factor Surveillance System (BRFSS) 2009 surveys and for public transport usage data, they utilized the 2009 National Household Travel survey data. The data they collected originated in 318 counties of 44 US states. They found that traveling by public transport was a good predictor of lower obesity prevalence. This is probably the case because using public transport requires more exercise than driving an automobile and thus is effective in reducing a sedentary lifestyle. This study is limited, as based on the methods used it cannot establish a causal relationship or in other words it cannot say that using public transport actually decreases obesity rates only that the more people travel by public transport, the lower the prevalence of obesity.

 Teacher only box

What do you think of such a program?  Do you think that this is an acceptable approach to addressing the obesity epidemic? Why or why not?

The requirement is for employers to give employees two breaks a day for exercise - not that all Chinese must get out and do calisthenics.  That being said, as a highly collectivistic culture, there could be strong peer pressure to do the exercises every day during the breaks. Students will vary in their opinions on whether this is an acceptable approach.

What do you think your government could do to promote exercise?

There are several potential answers here.  These include reducing health insurance premiums for those that engage in regular exercise, allowing tax deductions for gym fees, subsidizing gyms to encourage more gyms, sponsoring events that would allow for communal exercise.

On a personal note - the Czechs have an organization known as SOKOL - very similar to YMCAs around the world.  The goal of SOKOL was to encourage a healthy mind and body.  It also has strong patriotic links as well.  Here is a good site that looks at the history of the SOKOL organization. The philosophical (and psychological) links to the organization are very interesting.

A study conducted by Youlian et al. (2016) studied fourteen primarily African American communities which took part in the Racial and Ethnic Approaches to Community Health across the United States (REACH US) project. The goal of the project was to decrease obesity rates in selected neighbourhoods, as the prevalence of obesity is higher among the African Americans in the USA compared to the white population. The authors monitored these communities between the years 2009 and 2012 and then compared the outcomes of the intervention to the general population trends.

The intervention was community based - including health departments, universities, religious communities and the local YMCA. These groups worked to minimize the construction of new fast-food restaurants in the area. They also tried to motivate stores to offer more healthy food options in the community. They participated in the establishment of farmers' markets, produce stands and community gardens and attempted to implement policies in favor of pedestrians, cyclists, motorists and people using public transport. Furthermore, the coalition actively worked to create physical activity opportunities such as outside wellness and exercise areas and also to decrease the costs of gyms and other such facilities. Also, classes and workshops on nutrition and physical exercise were offered to the members of the communities. Finally, a campaign took place promoting the intervention in the form of newsletters, radio ads and posters. The results were positive, as the REACH US communities’ obesity rates overall decreased by 5.3% while the obesity prevalence for the control population actually increased by 2.4%. These results show that targeted interventions, which include the community, can be very effective in reducing obesity and may be an appropriate approach to use in order for the population to become heathier.

 Teacher only box

The students' own rankings of the six factors provide for interesting discussion.  Many of them focus on restaurant dining and corn syrup consumption.

When ranking for testability, there are several things to discuss:

• Most of these can only be tested with correlational data.  It would be possible to carry out natural experiments if a country stopped (or started) mandatory military service or expanded access to public transportation.
• It would be difficult to select a population to study for this research.  If the research were carried out on a national level, it would be difficult to monitor everyone's eating habits.
• There are several other variables that may play a role in obesity. These would have to be controlled; this could be done by matching participants for specific traits when analyzing the data.

Then, rank them again based on the "testability" of the hypothesis. Which of the six would be the easiest to determine whether the claim is valid?  How would you carry out research to test the hypothesis?

Finally, do a bit of research.  Which of these claims has been disproven?

Actually, none of these claims have been disproven; however, the one that is most disputed is actually the consumption of high-fructose corn syrup!  Here are some good links to help with discussions.

• Restaurant Dining
• Physical Education
• Mandatory military service
• Sidewalks and public transportation
• High-Fructose Corn Syrup Consumption (HFCS)
• Vending Machines

Checking for understanding