Summary: A life course approach to socioeconomic position and risk of prostate cancer
Christine Blaser, PhD, Belinda Nicolau, PhD, Gopal Netuveli, PhD, Marie-Élise Parent, PhD
Drs. Christine Blaser, Belinda Nicolau, Gopal Netuveli and Marie-Élise Parent were the first to study the effect of multiple related socioeconomic factors on the risk of prostate cancer. Instead of just assessing individual indicators at singular points in time, they made use of several which were measured across the entire life span, taking their collective impact into consideration. The researchers found little evidence for an effect of lifetime socioeconomic position on prostate cancer development or aggressiveness after examining both the direct effects of different indicators and the total indirect effects of accumulated lifetime exposure.
Prior to this study, it was known that social inequalities were associated with higher cancer incidence and mortality. It has been unclear, though, whether this held true for prostate cancer in particular. Since using only one indicator of socioeconomic position fails to provide an overarching view of the numerous factors that subtly intertwine to make up this resource- and prestige-based concept of social class, these four researchers examined six:
- Father’s occupation at birth, an indicator of childhood socioeconomic position
- Self-assessment of family’s childhood financial situation using a five-point scale ranging from very difficult to very comfortable
- Parents’ ownership of a car when the respondent was younger than 16, a marker of material living standards
- Education, measured using 8 categories ranging from ‘completed less than elementary school’ to ‘doctoral/postdoctoral level completed’
- Job class based on occupational history, with six possible options
- Income, with three categories (low, middle, high) based on family income before tax and number of individuals in the household
These indicators may be linked to lack of resources, unfavourable living conditions, or health-defying behaviour, all of which are likely to affect cancer incidence. This was an important step because while socioeconomic conditions can change over time, they may still trigger a cumulative chain of risk: for example, education level often depends on parents’ socioeconomic position and partly determines occupation, which is itself linked to income. The measures used were pulled from in-person interviews that collected socio-demographic, lifestyle, and occupational information from 1456 study participants who had newly confirmed prostate cancer cases, in addition to 1389 age-matched individuals without the disease from the same Montreal, predominantly French-speaking population.
The combined impact of the different indicators is telling: while having parents that did not own a car during childhood and very low education were both associated with an increased risk of prostate cancer when assessed on their own, the associations disappeared when the other indicators, as well as their real-life chronological order, were factored into the analysis. The researchers did not observe any other associations, including any based on recent prostate cancer screening, or health behaviours like tobacco smoking and excessive alcohol consumption. No information was collected on participants’ mothers’ education, smoking and stress during pregnancy. The small effect with education, though, may be a proxy for such data. Nonetheless, this study was a very comprehensive assessment of the effect of socioeconomic position from birth to retirement, especially given the relatively large sample and detailed data collection.