Smoking Cessation and Carotid Atherosclerosis - Report Example

Study Analysis Name Institution Course Lecturer Date 1) Research question Is smoking cessation beneficial in attenuating the risk of carotid atherosclerosis that is associated with cigarette smoking? The study relates both variables with time (duration of cessation) as an important factor to be considered on whether the risks reduce or not. 2) Type of study design The study used a cohort design that is common design in medical science. It was conducted over a period involving some members of a population where the subjects were to present the members in the overall population united in common similarities and commonality. Just as a major feature of cohort study; studying the effects of a variable on those already exposed and measuring risks, this study is involved with looking at smoking as a risk factor for a group that has already stopped. Secondly, cohort analysis is highly flexible and provides insight into effects over time with variety of changes. Similarly, the study has measured risk with environmental and occupational factors within duration of smoking cessation. A cross-sectional research would have been considered for the purpose of this research as it would involve data collection at a point in time and examine it to detect the patterns and trends in providing in-depth understanding of risk factors. Cross-sectional design has no time dimension and relies on existing differences rather than changes that follow intervention. In addition, the group would be selected on existing differences than random allocation. A variety of groups would be compared; those that continued smoking and those that ceased. 3) The study factor(s) Generally, the factors comprised of environmental, occupational, and genetic as well as life-style factors and determinants of common chronic diseases. Major cardiovascular risk factors included fasting triglyceride, high-density and low-density lipoprotein (HDL and LDL) glucose and cholesterol as well as systolic and diastolic blood pressure. There are quite a number of measurements employed by the authors in each case and at different phases of the study. A standardized questionnaire was used for assessing occupational exposure, lifestyle, cognitive function, family and personal disease history with smoking, physical activity and drinking status included. Blood pressures were measured through resting seated through automated sphygmomanometer. There were also well-trained interviewers that collected smoking history through the use of standardized questionnaire. Factors like age, education and physical activity were taken into consideration to measure the prevalence of risks across groups. Major factors including carotid plaque and CCA atherosclerosis were taken into consideration as they differed across the group and each factor has its associated risks that would be influenced by adjustment individual had made in the past. 4) The outcome factor(s) The outcome factors were identified by manifestation of carotid plaque and presence of CCA atherosclerosis among those who had quitted smoking. The mean of CCA-IMT and the number of carotid plaques were noted to increase from never smokers, former smokers to current smokers. Other factors like age, physical activity, education and body mass index were adjusted before determining the blood pressure (systolic and diastolic). The mean CCA-IMT also increased across the three groups respectively. Eventually, it was confirmed that the presence as well as severity of carotid plaque and CCA atherosclerosis were linked to smoking status with significant trends observed from never smokers, formers smokers to current ones. Similarly, significant trends were determined by the number of cigarettes smoked in a day and the number of years showing grater gradient between them. Both factors; carotid plaque and CCA atherosclerosis were all measured for the three groups of participants in the study in order to identify the differences that resulted after each factor was included like the duration, number of cigarettes and so on. 5) How cases were identified There was a criterion that was followed to obtain the cases for the study. Predominantly was the use of the past studies that were connected to smoking-related risks and cardiovascular diseases. Intima-media thickness and artery plaque were some of measures that had been used in the previous studies and measured according to their severity. Carotid IMT that is associated with risk factors were obtained from cumulative studies and was well-accepted for marking subclinical atherosclerosis. The cases were also obtained from hospitalized patients. CCA atherosclerosis manifesting thicker plagues or IMT were taken as they were associated with cardiovascular risk factors. Cross-sectional and other prospective studies had associated smoking with carotid atherosclerosis in Western populations and thus, the cases included would be identified through the manifestation of such factors. 6) The main findings of the study The study showed a reduction of risk involved with carotid atherosclerosis among those participants that were former smokers. The risk also decreased with increased duration of smoking cessation. Generally, carotid atherosclerosis were manifest in all the groups and that might be associated with multiple factors like age, lack of active physical activities and body mass index. However, for those who had stopped smoking, carotid atherosclerosis were less manifest and that made it easier to measure the duration from when participants quitted and the level of risk factors. There was indicated reduction of risks due to quitting. The comparison was done between the former and the current smokers where the former had lowered risk due to less prevalence of carotid atherosclerosis manifesting. For the group that had continued smoking, carotid atherosclerosis was more manifest and that meant that there was increased risk for the group. There were incomparable differences between smokers and never smokers in cardiovascular diseases risk factors. However, a number of parameters were worse in never smokers than smokers. Parameters like body mass index (BMI) as well as blood pressure offset the benefits of quitting. Carotid atherosclerosis is not only related to smoking but to quite an extent, lifestyle factors also account for increased risk factors. Simply, the study factors; carotid atherosclerosis were directly related to the outcome factors cardiovascular risks but there were other observable factors that increased the risk among the groups. 7) The association between the risk factor and outcome assessed Through the use of linear regression analysis, the effects of smoking showed thicker IMT among smokers and there was a higher risk in male gender and the pack-years of smoking. IMT thickness was associated with smoking. More sensitive endothelium functions were measured as to reflect significant differences between smokers and confirm the factors measured and the outcomes. The result on association was consistent and was in line with many Western populations that confirmed that cigarette smoking as associated with an increased CCA-IMT. Quitting duration was another important measure that was used in assessing and citing the differences between groups. The assessments were done in regard to the duration from the day the smokers quitted to cite the decrease of the risk factors. 8) Major sources of selection bias in this study Selection bias is highly noted in the study due to non-random sample of the population that was included in this study. Against what would be expected that study participants would be accessed from the general population of smokers and non-smokers, this cohort study restricted its sample to a group of participants who were hospitalized. While there was core reasons to have such a sample; including the potentiality of the group being accessible over time, the sample was not objectively represented as participants were not equally given a chance to be selected in the study. The sample can be said to have had a higher predictability of the study association and reduce the differences that would have been brought were other participants who were not hospitalized included in the study. Though the inclusion of such a group is applicable in multiple studies, in this study, it was not representing a population of former smokers that were outside hospital setting. Eventually, that might undermine the external validity of this test and the result may not be generalized to the population outside the hospital setting. There are a number of factors that could have facilitated the presence of a number of factors assessed like lower immunity and that would have resulted to a number of errors. There was no prescreening of participants to note their illness or disease that would have increased or made the outcomes to be closely associated to the factors being assessed. 9) Information bias Information bias is also highly prevalent in the study due to factors arising because of inclusion of a number of factors and the failure to account for the level of exposure for a particular group of people being assessed. Generally, the study has included some factors that have internal link with many factors. IMT thickness had quite a number of causes and thus, there was noted lack of differences for the groups of smokers and non smokers when factors like body mass index, age and level of activity were taken into account. Having many factors related to a particular outcome meant that there would be distorted evaluation of the cases and no single factor can be directly attributed to a certain outcome. Without a direct link, it always leads a number of categories being assumed to have their own level and contributing to overall result. There was an inclination of factors considered to hold the perspective seen in the outcome due to lack of precise way to conceive the prevalent factors. In turn, the study concluded that, the other parameters manifested and reduced the possibility of predicting the differences between groups. Ultimately, information bias was promoted by taking symptoms that manifested across the continuum of causative factors. 10) The issue of confounding Confounding was a major issue in the study and the authors dealt with it by having all factors considered together for all participants and noting the factors that would have influenced the study variables. Participants were included in phases to ensure that those with manifesting factors that would influence the variables were excluded from the subsequent assessments and thus exclude the impact of such factors. They restricted the study sample on the participants that were less likely to manifest significant factors that would in turn affect the study outcome in substantial way. There were a number of potential confounders that were noted to have manifested in the group that was being assessed. Age or the number of years for the participants, the body mass index, physical activity where participants were to indicate whether they had inactive, moderate or active lifestyle, blood pressure, fasting plasma glucose, total cholesterol and triglyceride. These were associated with the outcome and degree of severity for each case that were considered. 11) The association between the study factor and the outcome factor Age was an important factor and no wonder it was considered in the study. Young participants would have affected the study results and affected the association as they are counted as the healthy lot and able to resist a number of manifesting symptoms related to smoking risks factors. Older adults and elderly had reduced immune capabilities and were prevalent to cardiovascular risks factors that were measured and associated with smoking. Consequently, the study was constrained to those participants that aged 50 to 85 years in order to see how the long duration of smoking as well as long duration of cessation would impact on the outcomes of the risks factors. 12) In Table 4 were the results likely to be true effects The authors came up with distinct statistical models which represented most of the aspects that are to be considered in a CCA atherosclerosis and a carotid plaque case. The regression models also cover all the variables that are to be factored into the study. Apart from the accuracy of the models and analysis, errors that could have emerged in the results due to patients with missing data or patients with no physical activity were also eliminated through the exclusion of 27 patients. The 27 did not meet the set standards and criteria for analysis. The time frame of the study of the effects is also well distributed to allow for accurate results implying that the results on table 4 of the would most likely represent the true effects of smoking cessation as opposed to explanation by chance. 13) Which of the Bradford Hill’s criteria for evaluating causality Strength criterion is manifest in the study since there was a small association when all parameters were considered. Inclusion of parameters did not mean that there was no causal effect. There was a larger association with carotid plaques with smoking even if other parameters like BMI, age, physical activity and so on were also considered as prevailing factors. Consistency was noted as the findings observed in China with the included population were consistent with those studies in different places. Hence, the outcomes strengthened the likelihood of the effect being replicated in future studies as it is the case with the past studies. 14) Study be generalized to different populations The results can be generalized to different population as it took into account general factors that are accessible in any particular population. A factor that was considered and would be taken as unique on its own is level of education that is expected to differ across populations. In addition, level of physical activity might also differ significantly between populations but in regard to all the other factors including body mass index, age, duration of smoking and many others that were considered in the study can be easily accessible within any other population. In addition, the study did not emphasize on those factors that are not observable in all population. Biological factors are consistent across populations and to a greater extent, they compare between populations. References Jiang, C. Q., et al. (2010). Smoking cessation and carotid atherosclerosis: the Guangzhou Biobank Cohort Study—CVD. Journal of epidemiology and community health,64(11), 1004-1009. Read More