Essay: Green Spaces' Impact On Alzheimer's Risk In UK Adults - Study Review & Proposal.

Study 1

A large charity is seeking to fund a project to investigate the question, “How does exposure to green spaces affect the risk of Alzheimer's Disease in UK adults?” The charity received three applications with quite different study designs. Carefully read and review the details of each proposed study:

Study 1: 300 people in the UK aged over 60 with a diagnosis of Alzheimer's Disease recorded in their GP patient records and 600 controls without a diagnosis will be recruited from the charity’s mailing/telephone list. Participants will be interviewed about how much time they spent in green spaces in the 20 years before their diagnosis and grouped into high, medium and low exposure. Interviewers will also collect information on highest educational qualifications, employment type (or most recent employment type) and distance to the nearest recreational green space 20 years prior to diagnosis, as these are all considered to be potential confounders. Odds ratios will be calculated to estimate the association between daily walking and Alzheimer's Disease, conditioning on these confounders along with age, sex and GP practice.

Study 2: 1500 individuals in the UK aged over 65 years old will be recruited from the electoral register. A baseline assessment of cognitive and mental state will be carried out by a doctor (employed by the study) and participants with a diagnosis of Alzheimer's Disease will be excluded. Participants will use a GPS tracking wristwatch to record their daily movements for one month (starting from the anniversary of their study enrolment) during each year of follow up. This will be used to identify the average time spent in green spaces per day. Further assessments of cognitive and mental state will be carried out every five years by a doctor to identify Alzheimer's Disease. Rate ratios for Alzheimer's Disease will be calculated to examine the association between green space exposure and Alzheimer's Disease, conditioning on age, sex, highest education qualification and current/most recent employment type which will be recorded at baseline.

Study 3: 5000 individuals in the UK aged over 40 years will be recruited from GP practices during routine appointments. Participants will be excluded from the study if they have diabetes, rheumatoid arthritis, or Alzheimer's Disease.

Participants will fill in quarterly online or postal questionnaires describing their daily exposure to green spaces. The date of any diagnosis with Alzheimer's Disease in GP patient records will be recorded. Cumulative incidence ratios will be calculated to estimate the association between daily green space exposure and risk of Alzheimer's Disease, conditioning on current/most recent employment type, involvement in social activities, age and sex (all measured by questionnaire at baseline).

Discuss the relative strengths and weaknesses of the three proposals to the different study designs, populations, definitions of exposure and outcome, measures of association, potential sources of error and bias, ambiguity, and any other relevant concerns. You should consider - and report information on the occurrence of Alzheimer's Disease in the UK.

Outline and justify how you would conduct a better study to best answer the question, "How does exposure to green spaces affect the risk of Alzheimer's Disease in UK adults?” This may draw on elements from all, one, or more of the proposed designs and/or your own ideas.

Study 1- The proposal is based on a retrospective study where the participants will be recruited via the telephone list and charity mailing. The intent to conduct an observational study that was based on a case-control approach. The major strength of this study design can be accredited to the fact that this type of research helps in the determination of the rate of association between a range of risk factors and the major outcomes (1). Owing to the fact that the factors are responsible for affecting exposure, commonly referred to as risks of disease, measuring the impacts of time spent in green spaces among people diagnosed with AD and their non-diseased counterparts is a correct step. The population sampling is also accurate since the people belonging to the case group will be recruited from GP records (2). However, disparities between the case and the control group might lead to bias in the results. The researchers also proposed a correct method of collecting information about the exposure to green spaces and risk of AD.

Considering interview as the data collection method was beneficial since it is based on a personal type of research and provides the opportunity for direct interaction (3). However, some of the common sources of error that might arise in this research are namely, non-response error, specification error, measurement error, and selection error. The researchers did not mention the ways by which these errors could be averted (if any). The researchers proposed the calculation of an odds ratio. This would be a correct approach in determining the probability of exposure to green spaces in the control group. However, it would not help in establishing a correlation between AD and exposure, between patients in the case group (4). Moreover, two potential disadvantages of this research can be related to observation bias regarding information to exposure, and no calculation of absolute risks.

Study 2- The researchers have proposed an observational study, specifically a cohort study. The primary advantage of this research design can be attributed to the fact that it will allow the calculation of incidence rate of AD in the exposure group, and will also facilitate the evaluation of different impacts of the singe exposure (green spaces) (5). The researchers have proposed use of a GPS tracking wristwatch that will allow them to keep a track of the time spent in green spaces, and further determine its correlation with AD onset. Conduction of a baseline assessment is another strength since it will help in the establishing a point from which upcoming dimensions and calculations can be premeditated (6). Although the researchers have proposed measuring the daily movement during each follow-up period, the exact timeline of the study was not proposed. Rate ratio refers to the relative difference measure that is used for comparing the event incidence rates that occur at a certain point of time. The fact that the researchers have also cited the need of conducting cognitive and mental state assessments for diagnosing AD among the recruited individuals is a correct step.

Study 2

However, conduction of blood tests is also essential for ruling out the possibility of other dementia causes, apart from AD. Recruitment of a large sample size will increase the reliability of the results, thus facilitating the detection of statistically significant changes in the research (7). Although the researchers will adopt the strategy of purposive sampling that will allow them with necessary justification for drawing generalisation from the larger sample, the process can be greatly prone to researcher bias. The process might also lead to difficulty in defending sample representativeness. However, some of the weaknesses of the proposed study can be attributed to the fact that the researchers would have to follow a large number of participants for a long period of time. Furthermore, the study will be time consuming and expensive. Loss to follow-up refers to the participant who although actively contributed to the research at a certain point of time, often get lost or unreachable during follow-up period (8). Thus, differential loss to follow-up period might also result in introduction to bias.

Study 3- This study is another observational study that is based on cross-sectional design and will analyse the data from a certain population at a specific point of time. The major strength of this proposed research can be accredited to the fact that it will allow the collection of large cross-sectional data at little expense (9). Furthermore, owing to the fat that multiple variables will be considered during data snapshot, the findings can be analysed for supporting or negating the hypothesis. The age group of the participants is correct since early onset AD is a relatively rare type of dementia that affects people aged less than 65 years (10). However, apart from the age group the researchers did not mention about any other inclusion factor. The exclusion criteria that would eliminate participants who are not prospective of the intended research was correct. However, they could have written about exclusion of patients who have vascular dementia or fronto-temporal dementia. Use of questionnaires as the data collection instruments was a correct approach as they will allow collection of responses from several participants. Although the researchers did not mention the type of questionnaire that will be used, from their statement it can be deduced that the participants will be made to describe their exposure to green spaces (11).

Hence, it can be suggested that unstructured questionnaires will be used for the research. One advantage of this data collection method is that the respondents can provide answers in any way, thus leading their interview. However, coding the answers of the questionnaire often results in distortion of the distinct answers that are provided by the individuals. The researchers have proposed the calculation of cumulative incidence that will be assessed as the number of new cases of AD divided by total participants of the study. This will prove useful since it will help in determining the probability of disease development over a definite period of time. However, the authors did not mention about the time span that the study will encompass. Furthermore, conduction of the cross-sectional study will not determine the cause and effect.

Study 3

A better study can be conducted in terms of a quantitative research design where an observational study will be conducted for 2 successive years, with the study beginning a year before the opening of wander gardens and a year of assessment after the event. An estimated 50 people will be recruited from primary health care centres who do not report any chronic conditions and age aged more than 55 years of age. They will be selected if they do not have access to green spaces near their household or locality. A year of assessment, prior to their interaction with the green spaces would involve early detection biomarkers, blood tests, neuroimaging, mild cognitive impairment and cerebrospinal fluid proteins. Furthermore, the global Clinical Dementia Rating (CDR), Mini Mental state examination (MMSE), and Functional Activities Questionnaire (FAQ) will also be used (12) (13). Following recording of all the baseline scores, the participants will be asked to access the wander garden. The number of day and hours that they spent in the region will be rigorously recorded. After a year, the same assessments shall again be conducted to obtain the scores. Vivid statistics, regression analyses, and Pearson’s correlations, will be used for examining the association of wander garden habit to the final scores, in order to determine AD risks. All the variables will also be subjected to bivariate Pearson correlations. The risk of association will also be calculated by odds ratio (OR) that will help in determining whether the exposure of the participants to green spaces increased or decreased their risk of AD.

References

Punch KF. Introduction to social research: Quantitative and qualitative approaches. Sage; 2013 Nov 19.

Levy PS, Lemeshow S. Sampling of populations: methods and applications. John Wiley & Sons; 2013 Jun 7.

Alshenqeeti H. Interviewing as a data collection method: A critical review. English Linguistics Research. 2014 Mar 29;3(1):39.

Grant RL. Converting an odds ratio to a range of plausible relative risks for better communication of research findings. Bmj. 2014 Jan 24;348:f7450.

Woodward M. Epidemiology: study design and data analysis. Chapman and Hall/CRC; 2013 Dec 19.

Lindsay G, Desforges M. Baseline assessment: Practice, problems and possibilities. David Fulton Publishers; 2013 Nov 26.

Etikan I, Musa SA, Alkassim RS. Comparison of convenience sampling and purposive sampling. American Journal of Theoretical and Applied Statistics. 2016 Jan;5(1):1-4.

Howe LD, Tilling K, Galobardes B, Lawlor DA. Loss to follow-up in cohort studies: bias in estimates of socioeconomic inequalities. Epidemiology (Cambridge, Mass.). 2013 Jan;24(1):1.

Lebo MJ, Weber C. An effective approach to the repeated cross?sectional design. American Journal of Political Science. 2015 Jan;59(1):242-58.

Alzheimer’s A. 2015 Alzheimer's disease facts and figures. Alzheimer's & dementia: the journal of the Alzheimer's Association. 2015 Mar;11(3):332.

Salter NP, Conneely MR. Structured and unstructured discussion forums as tools for student engagement. Computers in Human Behavior. 2015 May 1;46:18-25.

Williams MM, Storandt M, Roe CM, Morris JC. Progression of Alzheimer’s disease as measured by Clinical Dementia Rating Sum of Boxes scores. Alzheimer's & Dementia. 2013 Feb 1;9(1):S39-44.

Bezdicek O, Stepankova H, Novakova LM, Kopecek M. Toward the processing speed theory of activities of daily living in healthy aging: normative data of the Functional Activities Questionnaire. Aging clinical and experimental research. 2016 Apr 1;28(2):239-47.