Sampling frame for each phase of the Whitehall study
Sampling frame commonly refers to the source devise or material from which samples are drawn. Thus, sampling frame incudes a list of individuals/houses/institutions that can be sampled, within a population. The Whitehall study I included a sample that was selected from British civil servants, all male during the 1960s. Approximately 19029 men from the selected population, all aged between 40-69 years were recruited for investigation between the 1967-1970s, for identifying the risk factors that lead to the incidence of cardiovascular diseases. No women were included in the sampling frame for the first study. The Whitehall study II selected participants from a new sampling frame that comprised of 10314 British civil servant, comprised of men and women, aged 35-55 years. The cohort for the second study included 3414 women and 6900 men. This study was conducted from 1985-1988 and investigated the cause and degree of social gradients in morbidity in the new cohort.
Disease risk assessment
The study conducted by Breeze et al., (2001) resurveyed 400 survivors of the pilot study conducted in 1997-1998. Data collection was conducted by distributing questionnaires to the individuals that included questions on retirement and socioeconomic status, diagnosis of diseases, and ability to carry out daily activities. Thus, the researches assessed the disease risk by collecting information on 4 aspects of self-reported morbidity that encompassed poor physical performance, mental health, general health and disabilities. Data analysis was conducted by chi-square tests for determining univariate associations between the aspects. Odds ratio estimation was done with the use of a logistic regression model.
Marmot et al., (1978) collected data for assessing the risks of coronary heart disease by distributing London School of Hygiene Cardiovascular Questionnaire that focused on several items, including employment grade. Use of this questionnaire can be cited as a correct method for defining the risks that might predispose a person to cardiovascular disorders such as, angina pectoris. Putting forth questions related to respiratory symptoms, smoking history, leisure activities, medical treatment and ECG were an effective data collection method. Data analysis was conducted by age adjustment and multivariate analysis that involved an observation and analysis of several statistical outcomes at one time. Calculation of the relative increase in risks for major factors was an appropriate step for risk assessment.
The study conducted by Chandola et al., (2007) collected data for evaluating the association between heart disease and work stress with the use of the job-strain questionnaire. Use of this self-assessment questionnaire helped to determine the psychological and social characteristics of the jobs that the respondents were engaged in. This helped to evaluate the relative risk of exposure to different work setting for predicting coronary heart disease and job related distress. Adding cumulative measures of work stress and use of the Cox proportional hazard regression model helped to determine association between stress and cardiovascular events.
Generalisation of results
Generalisation involves the process of drawing inference from certain observations and is acknowledged as a major standard of quantitative research. The results of the findings by Breeze et al., (2001) can be generalised to the entire population since multimorbidity was found prevalent among individuals belonging to the lower socioeconomic sections of the society. Owing to the fact that socioeconomic status creates an impact on the morbidity and disability status of individuals, the findings that illustrated an association between SES in retirement, disadvantage accumulation and poor health status can be generalised to a larger population.
The results by Marmot et al., (1978) can also be generalised since it established a link between grade of employment and risks of cardiovascular diseases. Owing to the fact that employment condition is a major social determinant of health, poor employment status will lead to poverty and increase the chances of suffering from poor health.
Association between work related stress on CHD, as stated by Chandola et al., (2008) can also be generalised since heavy workload, job insecurity and conflicts have already been identified as psychological risk factors that increase the susceptibility of suffering from heart disorders.
Feasibility of studies refer to practicality of certain methods or plan. The 45 and Up cohort can be selected for conducting a risk assessment of cardiovascular disease. The cohort was comprised of one in 10 men and women from the NSW, aged over 45 years. The cohort was built with the aim of investigating healthy aeging among the selected individuals. Risk assessment of cardiovascular diseases can be conducted among the cohort by distributing self-reported questionnaires, since men have been found at a risk of CVD above 45 years of age. However, prevalence of CVDs among women aged more than 55 years, might produce bias in the results.
Moreover, lack of availability of clinical diagnostic results will also limit the feasibility of the cohort. Use of the Australian Longitudinal Study on Women’s Health is not reasonable since the new cohort formed in 2012-13 included 17000 women aged 18-23 years and determined their physical and mental health, in addition to lifestyle factors and socio-demographic factors. Unlikelihood of using this cohort for determining the risks of CVDs can be established by the fact that only 4-10% of heart diseases occur before the age of 45. Moreover, heart attacks and other cardiovascular abnormalities are twice as common in males as females, during the lifespan. Considering the fact that the cohort takes into account only females, the results are likely to be biased upon conduction of the study.
Ill health preceding low socioeconomic status, cumulation of psychological stress, and material resource disadvantage could have resulted in variations in the outcomes of the baseline and resurvey (Breeze et al., 2001). Limitations of the second research were associated with self-selection of men belonging to the low employment grades that might have resulted in obtaining stronger mortality gradient among the respondents (Marmot et al., 1978). Other limitations were related to lack of consideration given to leisure related physical activities, since the study was primarily based on men working in physically undemanding occupations. Missing data in the Whitehall cohort, based on which the third study was conducted was another major limitation that might have resulted in bias in the results that showed association between work related stress and coronary heart disease (Chandola et al., 2008).
Breeze, E., Fletcher, A. E., Leon, D. A., Marmot, M. G., Clarke, R. J., & Shipley, M. J. (2001). Do socioeconomic disadvantages persist into old age? Self-reported morbidity in a 29-year follow-up of the Whitehall Study. American journal of public health, 91(2), 277.
Chandola, T., Britton, A., Brunner, E., Hemingway, H., Malik, M., Kumari, M., ... & Marmot, M. (2008). Work stress and coronary heart disease: what are the mechanisms?. European heart journal, 29(5), 640-648.
Marmot, M. G., Rose, G., Shipley, M., & Hamilton, P. J. (1978). Employment grade and coronary heart disease in British civil servants. Journal of Epidemiology & Community Health, 32(4), 244-249.