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Critique of Quantitative study of Hypertension

The research problem outlined by Gangavati et al. (2011) is the lack of understanding of the connection between controlled and uncontrolled hypertension, orthostatic hypotension, and the risk of falls among the elderly people aged 70 and more. The authors emphasized the seriousness of the problem by stating that falls are nowadays regarded as the most frequent cause of disability in the old age, while orthostatic hypotension (OH) is a common cause thereof. OH is presumably caused by the hypertension control medications that people with hypertension take. At the same time, OH is seen as the direct cause of falls; however, there is a pronounced lack of research evidence that explores the relationships between falls, OH, and hypertension in more detail. Taking into account the gravity of falls’ consequences, the problem is characterized as topical and urgent for the public health.

Taking this problem statement into account, Gangavati et al. (2011) aimed to analyze the relationships between uncontrolled and controlled hypertension, OH, and falls in their study. Their purpose was achieved by means of involving the participants of the Maintenance of Balance, Independent Living, Intellect, and Zest in the Elderly of Boston Study. The preliminary hypothesis of the researchers assumed that the increase in the risk of falls was associated with uncontrolled hypertension and the presence of OH. Hence, the objective formulated for this study included studying the correlation between hypertension, OH, and the risk of recurrent falls in the community-dwelling elderly population (Gangavati et al., 2011).

The literature review conducted to set the context of the present study is quite short, and is not separated from the introductory part of the article; before proceeding to the methods section, the researchers outlined the strong and weak research evidence related to the issues of controlled and uncontrolled hypertension, OH, and falls. The authors indicated that the connection between falls and disability is an established medical fact, and OH being the prime reason for falls has also been clinically proven. However, there is still a significant gap in the research literature regarding the interrelationship among hypertension, OH, and falls has been detected by the researchers. Gangavati et al. (2011) claimed that the data available at present on the subject of interest have been collected in the nursing homes only, and there is a dramatic lack of empirical evidence from the community-dwelling elderly people also experiencing this problem.

Another research gap identified by the researchers refers to the issues of controlled hypertension and its effect on the emergence of OH symptoms. Gangavati et al. (2011) cited the results of prior research indicating that lowering and controlling hypertension is usually associated with the development of OH, and contrasted these findings with the analysis of the National Health and Nutrition Examination Survey that indicated that OH is less prevalent in old people with controlled hypertension. The present contradictory research findings from prior research imply that the connection between hypertension and OH is not clearly understood yet, and there is a need for further clinical research for the sake of clarifying the issue.

Moreover, the absence of clear research findings defining OH in relation to falls also served as an additional impetus for conducting the present study. As Gangavati et al. (2011) found out, some prior studies indicated that a 20mmHg decrease in systolic blood pressure (SBP), or a 10mmHg decrease in diastolic blood pressure (DBP) is associated with falls in case the person performs standing for more than 3 minutes. However, some other clinical investigations did not show any relationship between falls and OH if the present conditions were used. The measurement of BP before 3 minutes of standing pass was expected to give more accurate data on the connection of OH to falls, which is the clear gap in clinical research – such studies have never been conducted before. To address this gap in the medical literature, Gangavati et al. (2011) intended to study the relationship between hypertension, OH (using multiple definitions thereof) after 1 and 3 minutes of standing to compare the association of OH with falls in these different conditions.

There is no theoretical framework explicitly laid out in the study of Gangavati et al. (2011). However, there is an indication that the theory on which the researchers relied in the process of their study is that of the existing relationship between hypertension and OH, and the connection of OH with falls. The contradictory clinical evidence does not allow making concise conclusions on the point, though there is a growing body of research implying that a certain form of relationship between blood pressure and falls still exists, especially for the elderly people.

The research design of the present study is represented by a prospective, population-based study on the risk of falls for older adults. It is formally titled the Maintenance of Balance, Independent Living, Intellect, and Zest in the Elderly of Boston Study (MOBILIZE study). The research design of the present study also implied getting the informed consent from the respondents, and the IRB approval for conducting it was initially received from the Hebrew Rehabilitation Center’s institutional review board (Gangavati et al., 2011).

Though the IRB approval was mentioned in the study, there is no explicit information in the article about the way in which the human subjects were protected in the research process. The sample selected for the study included elderly people aged 70 and more living at not more than 5-mile distance from the Hebrew Rehabilitation Center in Boston. The inclusion criteria used for the compilation of the study sample included the age of respondents being 70 and more, basic knowledge of English that would not impair communication and understanding, and the ability to walk 20 feet without other people’s assistance, though the mechanical walking assistance devices were permitted for use. Moreover, to be included into the sample of the study, the participants were tested for having sufficient vision to be able to study the research material independently, and were questioned about their plans for residing in the area for the next 3 years (Gangavati et al., 2011). The exclusion criteria for the chosen sample included the participants with a follow-up within less than 6 months, those with terminal diseases, deficits of vision and hearing, or cognitive impairments.

The research setting was as follows: the simple random sampling procedure was used for the identification of potential participants from the won lists, and the chosen people were later contacted by mail, or were visited at home by the recruitment staff (Gangavati et al., 2011). After providing their informed consent to the participation in the study, the participants underwent the baseline assessment consisting of two stages. The interview that lasted about 3 hours was conducted in their home settings; it included the clarification of such background information about the participants’ state of health as “medical history, fall and syncope history, cognition, medications, and socio-demographic information” (Gangavati et al., 2011, p. 384). The initial interview contact was followed by a clinical investigation of the same length in about a month afterwards targeted at identifying the participants’ mobility performance, balance, vitality of muscles, and the postural BP indicators (Gangavati et al., 2011).

The data collection process took place within one year, with the initial assessment and the follow-up censorship between 6 months and 1 year. The participants were initially divided into three groups – those without hypertension, with BP lower than 140/90mmHg, and with no history of hypertension and taking anti-hypertension medications were included into the first group. The second group constituted the hypertensive respondents who controlled hypertension with medications, and had the BP lower than 140/90mmHg. The third group included the uncontrolled hypertensive respondents with BP higher than 140/90mmHg. The collection of falls-related data was undertaken by means of collecting the falls calendars kept by respondents at home, and handed in to the research center at the end of each month (Gangavati et al., 2011).

Measurement of independent and dependent variables relevant for this study involved the measurement of BP, and ascertainment of falls (Gangavati et al., 2011). The BP measurement procedure was conducted by trained professionals knowledgeable about the potential sources of error such as “expectation bias, terminal digit preference, auscultatory gap, pseudo-hypertension, and cardiac arrhythmias” (Gangavati et al., 2011, p. 384). The BP measurement process took place with proper regard to standardized techniques, participants resting every 5 minutes, the choice of the correct cuff size, and close attention to the auscultatory gaps. The SBP and DBP indicators were obtained two times with the interval of 2 minutes, upon the patient’s recumbence for at least a 5-minute period. The tool for SBP and DBP measurement was a standard sphygmomanometer. The measurements were repeated 1 and 3 minutes after standing, cuff being kept at the heart level; the means of measurements were taken for analysis, and the measurement was undertaken in 2 hours after breakfast or lunch (Gangavati et al., 2011).

The ascertainment of falls was undertaken independently by the participants who were asked to keep a monthly falls calendar, and hand it back in to the study center at the end of each month. An “F” mark was put in case a fall occurred, while an “N” mark meant the absence of falls on a particular day. The team of geriatricians and investigators held the responsibility for adjudicating the falls, and respondents were included into the group of fallers after two falls. The present consideration is explained by the assumption that multiple falls rather than only one instance of falls can imply an underlying medical pathology (Gangavati et al., 2011).

The data analysis process was conducted by means of applying the statistical analysis procedures. Taking the follow-up range from 183 to 365 days, the researchers censored fallers at the time of the reported second fall, while non-fallers were censored upon spending a year within any falls (or with one fall) (Gangavati et al., 2011). The characteristics of all three groups were statistically correlated with the help of applying chi square for bivariate variables, Fisher exact tests for categorical variables, and Wilcoxon rank sum for continuous variables (Gangavati et al., 2011, p. 384). An additional data analysis method used in this study was stratified analysis – it aimed at identifying the connection that a combination of hypertension and OH might have with the fall risk. The use of Kaplan-Meier curves and multivariate Cox proportional hazard modeling allowed the researchers to correlate the risk of falls, OH, and individual characteristics of respondents.

The presentation of findings in the article of Gangavati et al. (2011) is appropriately organized, and covers all variables of interest. The sample that included respondents with more than 6 months of follow-up included 722 people. The percentage of people without hypertension, with controlled and uncontrolled hypertension was provided, and the number of respondents who had OH was also provided according to categories thereof. The number of fallers was analyzed with reference to OH, and the risk of falls was also statistically stratified. Hazard ratio was calculated, and the Kaplan-Meier curves for the risk of falls were generated. The results part also contains a very detailed and illustrative table with the systematized baseline characteristics according to the hypertension status of the MOBILIZE study.

The discussion of findings is very detailed, and covers all aspects of risks associated with falls. The participants with uncontrolled hypertension were revealed to suffer a risk of falls 2.5 times higher than those with controlled hypertension, and lower standing SBP was also strongly associated with falls. However, the researchers still indicated that the research evidence is not sufficient to draw any clear lines of correlation between high blood pressure, OH, and falls. Additional contributors to the development of OH (besides BP) include “baroreflex-mediated cardio-acceleration and vasoconstriction, impaired renal salt and water conservation, and slow cardiac filling” (Gangavati et al., 2011, p. 385). Hence, there is no direct link between high BP and OH, since aging is a serious contributor of OH development regardless of BP indicators.

The valuable finding of Gangavati et al. (2011) is that SOH at 1 minute is a high predictor of falls, and that older adults with ventricular vascular stiffening may be at a greater risk of developing OH. The present findings are very interesting for clinical practice, since many clinicians refused from controlling hypertension of older people and lowering it to 140/90mmHg and lower because of the fear to contribute to the development of OH, which was empirically proven to be not the case. The findings of Gangavati et al. (2011) also imply that the OH should be measured not at 3 minutes, but at 1 minute of standing, which provides the measurements with additional sensitivity.

The authors drew a concise conclusion from their study, indicating that the prevalence of OH was estimated as higher for participants with uncontrolled hypertension, with the risk 2.5 times higher with OH 1 minute after standing than for those who had no OH (Gangavati et al., 2011). The present study has a wide range of implications for theory and clinical practice, since, as Gangavati et al. (2011) noted, there is a common fear among geriatricians regarding artificial lowering of BP for elderly people because of the false perception that BP control can cause OH. As the present clinical trial proved, there is no such threat, and uncontrolled hypertension is much more frequently associated with OH and falls than controlled hypertension is. Therefore, these findings can be applied in the geriatrics practice in the hypertension and OH management for the sake of preventing the recurrent falls among elderly people.

References

Gangavati, A., Hajjar, I., Quach, L., Jones, R. N., Kiely, D. K., Gagnon, P., & Lipsitz, L. A. (2011). Hypertension, Orthostatic Hypotension, and the Risk of Falls in a Community-Dwelling Elderly Population: The Maintenance of Balance, Independent Living, Intellect, and Zest in the Elderly of Boston Study. Journal Compilation: the American Geriatrics Society, 59(3), 383-390.

 

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