Risk of Breast Cancer in Night Shift Work - Report Example

Epidemiology studies Program: Supervisor: April 30, Epidemiology studies Knowledge on risk factors to a health concern plays important role in prevention and management of the concern. Statistical data that supports significance of a risk factor to a problem is for example an indicator of the need to take adequate measures on the factor. Ability to interpret statistical reports and to evaluate their reliability and validity or their consistency and credibility is therefore important before possible application. This paper reviews two articles on significance of night shift on women’s susceptibility to breast cancer in order to facilitate awareness among women in a facility and among the facility’s management and to recommend necessary policy measures based on the analysis of the articles. Night shift work, light at night, and risk of breast cancer The study by Davis, Mirick and Stevens was based on the hypothesis that exposure to light during night shifts increases risks of breast cancer. The authors’ results support the hypothesis but validity and reliability of these findings are based on the study’s data collection, data analysis, and data interpretation. Data collection The study aimed at investigating potential relationship between exposure to light at night and risk of breast cancer in women with effects of light at night on generation of melatonin that in turn affects susceptibility to breast cancer, as the association of interest. Risk of breast cancer was the primary outcome of interest. Interview was used to collect information on participants’ history as a measure to the outcome variable and this identifies validity concerns. The considered factors in measuring the outcome variable are not precise to an individual’s risk of breast cancer for a correlation analysis and the study’s objective. In addition, interview is not a reliable data collection technique because it is susceptible to bias. Participants could for example report history that identifies with breast cancer while such information could be false. Screening measures for breast cancer that are more accurate could be appropriate. Sleep patterns and habits were the primary exposure of interest and like in the measure for outcome of interest; the data collection technique is inaccurate due to lack of precision and potential bias (Davis, Mirick, and Stevens, 2001). The study applied a case control approach with survey as its design. A significantly large sample size was applied and random sampling used, and these factors eliminated biased and ensured representation. Classification into control and case groups was however accurate. No restrictions, such as elimination of individuals, who recently participated in studies with similar measures, was placed in sampling and design and this exposed the study to history confounds. Maturation and instrumentation confounds could also be significant in the study that considered data over a long period (Davis, Mirick, and Stevens, 2001). Data analysis The study reports no control measures against confounding bias. Odds ratio was the measure of association between the exposure of interest and outcome of interest and this was appropriate because of the categorical nature of the considered data for both exposure and outcome variables. Stability of measure of association was reported through both confidence intervals and through p-value statistics (Davis, Mirick, and Stevens, 2001). Interpretation of data The study’s results identify higher risk of breast cancer among individuals who lacked sleep at night and the risk was greatest among those who did not sleep at the time of formation of melatonin. In addition, higher brightness of light in rooms, at night increased risks to breast cancer. The results also identify a positive relationship between risk of breast cancer and graveyard-shift work. These results are interpreted to mean that exposure to light at night increases risk factor to breast cancer. Noted bias due to data collection method could however lead to type one error. Negative attitudes towards lack of sleep and exposure to light at night could have influenced responses to indicate association between the variables. Non-differential miscalculation could have also affected the interpretation through poor control because the control approach did not relate to the measured variables. The results could be generalized to the entire population of women above the age of 20 because classification was done by age groups and identified significance. The large sample size and representativeness also facilitate generalization. The study is not explicit in its discussion of limitations but suggests limitations in data collection instrument and interview questions. There was no formal conclusion (Davis, Mirick, and Stevens, 2001). Rotating night shifts and risk of breast cancer in women participating in the nurses’ health study Data collection The study aimed at investigating effects of night shift on susceptibility to cancer. Occurrence of cancer is therefore the outcome of interest and the measure was accurate through verification of participants’ history. Statistical methods were also used to determine risk of cancer. Number of hours on night shifts worked is the primary exposure of interest and reliance on participants’ accuracy and integrity casts doubts in accuracy of its measure. The study was a prospective cohort design. Convenience sampling was employed, based on nurses’ willingness to engage. This further undermines potential bias in sample selection. Reliance on interviews for data on night shift however identifies potential non-differential miscalculation due to respondents’ bias. Maturation confound, due to the longitudinal scope of the study was possible (Schernhammer, Laden, Speizer, Willett, Hunter, Kawachi and Colditz, 2001). Data analysis No control measure was done against the potential confound. Relationship between risk of cancer and number of hours of night shift was reported, based on involved number of years and this was appropriate because of suitability of level of measurement for both outcome and exposure measures. Confidence interval was used to report stability of the measure of association (Schernhammer, et al., 2001). Interpretation of data Increased risk of breast cancer by period within which a nurse worked on night shifts is the major result for the study. There was absence of significant confound, and miscalculation that could affects interpretation of the results. The findings can be generalized to the woring population of female nurses and the large sample size and unbiased sampling support this. the authors report possible limitation in random miscalculations and confounding factors. The study also offers a formal conclusion that recaptures its major findings and possible implications (Schernhammer, et al., 2001). Conclusion The study by Davis, Mirick, and Stevens identifies a relationship between risks of breast cancer and number of hours of night shift based on lack of sleep and brightness of light that nurses are exposed to at night. Reliability and validity concerns over the study’s data collection approach however undermine the study’s conclusion as it fails to offer a strong basis for correlating the considered variables. This further exposes the results to bias and other factors outside the researchers’ variables of interest. Consequently, findings of the study should not alarm the women and the management should not rush to implement policies because this could be unnecessary. The second study, by Schernhammer, et al., however has a significant level of validity and reliability. The study’s results that working on night shift for many years is a significant risk factor to breast cancer is therefore valid and the women needs to worry. The management can however ensure safety by limiting night shift work to younger employees. References Davis, S., Mirick, D. and Stevens, R. (2001). Night shift work, light at night, and risk of breast cancer. Journal of the National Cancer Institute, 93(20), 1557-1562. Schernhammer, E. et al. (2001). Rotating night shifts and risk of breast cancer in women participating in the nurses’ health study. Journal of the National Cancer Institute, 93(20), 1563-1568. Read More