Part 1
One study addressed the relative roles of genes and environment on the diagnosis of Alzheimer’s disease (AD) (Gatz et al., 2006). Based on this research, the article estimates that variance in Alzheimer’s disease diagnosis is 58% due to additive genetic influences (A=.58), 19% due to shared environmental influences (C=.19), and 23% due to non-shared environmental influences (E=.23). Given these estimates of A, C, and E, AD is only somewhat malleable. Meanwhile, shared environmental influences and non-shared environmental influences are estimated to play approximately equal roles in the variance in Alzheimer’s disease (.19 ~=.23), and are collectively less likely to influence than additive genetic influences. Other environmental factors that are likely to influence diagnosis of AD may include exercise and diet. For instance, one AD and exercise-related study in transgenic Alzheimer’s disease mice found that voluntary exercise reduced the pathology of Alzheimer’s, specifically the beta-amyloid plaques, in the frontal cortex and in the hippocampus (Adlard, Perreau, Pop, & Cotman, 2005). If these results translated to human subjects, the findings in this study may suggest that exercise yields a protective benefit against AD diagnosis. Diet may be another environmental factor with some influence on AD diagnosis. For instance, one study found that closer adherence to the Mediterranean Diet — which is characterized in part by high intake of vegetables, legumes, fruits, cereals, unsaturated fatty acids and fish– is associated with lower risk of AD (Scarmeas, Stern, Tang, Mayeux, & Luchsinger, 2006). Both diet and exercise could play into shared and non-shared environmental influences. For instance, if twins grew up in the same household, it is likely that their diets were similar during that time (shared environmental influence), but their diets may have diverged when they grew older (non-shared environmental influence). Similarly, twins growing up in the same environment may have had similar exercise habits under the same roof, but might have diverged in their exercise habits after growing up and living apart. In addition to diet and exercise, some evidence supports an association between playing a musical instrument and a lower likelihood of AD diagnosis (Balbag, Pedersen, & Gatz, 2014), which could be a shared or non-shared environmental influence as well.
All in all, this study was effective in operationalizing its dependent variable, Alzheimer’s disease, through current criteria provided by the National Institute of Neurological and Communicative Disorders and Stroke and Alzheimer’s disease and Related Disorders Association (NINCDS-ADRDA). Its participants were from the Swedish Twin Registry, which makes the participants from a population-based sample. However, the paper cites no information related to race or ethnicity, which prevents the verification that the Swedish Twin Registry population is representative on an international or global scale. Finally, the study does draw appropriate inferences given their study design and results. For instance, it states that “The results of the present study… provide important evidence for the extent to which environment influences disease occurrence” but does not attempt to make unsubstantiated claims based on these results.
Another study investigates the impact of music playing on the likelihood of dementia and cognitive impairment diagnosis (Balbag et al., 2014). Although the study does not directly address AD diagnoses, its results remain very relevant: dementia and cognitive impairment are diagnosed based on behavioral symptomatology, whereas Alzheimer’s can only be fully diagnosed through assessment of physical manifestations of AD, which can be discovered though autopsy after death. Because of this distinction, symptoms required for diagnosing dementia and cognitive impairment are often explained by a diagnosis of AD after death. In this way, results regarding dementia and cognitive impairment are still highly relevant. Furthermore, two-thirds of this study’s dementia population was diagnosed with AD.
The study specifically explored the question of whether, in twin pairs where one twin played an instrument while the other did not, the non-musical twin is more likely to be diagnosed with dementia or cognitive impairment than the music-playing twin. The results showed that playing a musical instrument is associated with a decreased likelihood of having dementia or cognitive impairment (OR = .36). This translates to a Pearson correlation coefficient of .27, or a roughly medium effect size. Given this medium effect size, specifically encouraging people to play musical instruments in order to reap this reward may have a only a modest influence on the likelihood of dementia (and, indirectly AD) diagnosis if the relationship between playing a musical instrument and avoiding dementia and AD diagnosis were causal. However, given the psychological and financial expense of caring for individuals with dementia and AD, even a small positive benefit is likely worth the effort of facilitating music playing. Overall, this study was effective in operationalizing its dependent variables, dementia and cognitive impairment, using a canonical manual for mental disorders, the Diagnostic and Statistical Manual of Mental Disorders IV, while AD was diagnosed using criteria from criteria from NINDS-ADRDA. The Swedish Twin Registry was used as a population-based participant pool. Though large in size, this study makes no reference to the Swedish Twin Registry’s diversity in terms of race or ethnicity, thereby calling into question the Registry’s generalizability across national and global populations. Finally, the inferences drawn by this study were appropriate. For instance, the study concludes that “musicians playing an instrument in older adulthood had a 64% lower likelihood of developing dementia or cognitive impairment” but does not stretch this finding to discussion of a causal relationship between playing a musical instrument and avoiding dementia or cognitive impairment.
Part 2
Between 6 and 10 percent of adults in North America aged 65 years and older have dementia, and 66% of those cases are attributable to AD (Hendrie, 1998). Research has suggested that variance in diagnosis of AD is 42 percent attributable to environmental factors (Gatz et al., 2006), indicating that environmental factors may be a useful means of lowering the likelihood of AD diagnosis. One environmental factor that has been associated with a protective benefit against AD is playing a musical instrument; one study found a 64% lower likelihood of developing dementia or cognitive impairment – behavioral symptoms often caused by AD— in older adults who play an instrument compared to older adults who don’t. Although this study resulted in just a modest effect size, the benefit of even a modest effect should be weighed against the financial and psychological expense of caring for patients with a disease which bears so much influence on affected individuals’ experience of the world.
Here, a two-pronged policy recommendation is proposed to capitalize on potential benefits of musical instrument playing in older adults. First, we propose government funding of music lessons for individuals over the age of 60, the age at which approximately 25 percent of people have begun developing amyloid-beta AD pathology (Braak, Thal, Ghebremedhin, & Del Tredici, 2011). Second, we propose funding for musical practice spaces for older adults with musical experience who lack space or instruments to play. Together, these recommendations may increase music playing involvement for individuals at-risk for developing AD.
Part 3
In order to establish whether there is causality between playing a musical protecting against Alzheimer’s disease diagnoses, we propose a longitudinal study of elderly monozygotic twin pairs starting at age 60 to 65. The participant pool would specifically be 10,000 twin pairs with equal numbers of males and females, evenly distributed across the ages of 60 to 65, with a distribution of religion, race, ethnicity and socioeconomic status that is representative of the world’s population. Such a population would not be explicitly selected by experimenters, but instead would be part of an international twin registry, and all participants in such a registry would consent to participation in this study. In such a study, both twins in each twin pair would have little or negligible musical experience. In particular, neither of them will have ever 1) taken a formal music lesson or 2) taught themselves an instrument. Then, one randomly assigned twin in each twin pair would be asked to take music lessons and practice an instrument two to three times a week. In this way, music playing is defined by practicing a musical instrument two to three times per week for one hour at each sitting. This variable is manipulated in the sense that one twin will play a musical instrument by the parameters stated above, while the other twin will continue to have negligible musical experience. Alzheimer’s disease would be quantified using the most recent criteria from the National Institute of Neurological and Communicative Disorders and Stroke and Alzheimer’s disease and Related Disorders Association (NINCDS-ADRDA) (McKhann et al., 2011), which has been used in related studies as a measure for probable AD (Balbag et al., 2014; Gatz et al., 2006). Participants would be administered the NINCDS-ADRDA criteria to diagnose AD on a yearly basis over the course of the study. Finally, the data will be analyzed to determine whether participants in the musical-instrument playing condition had a lower instance of being diagnosed with Alzheimer’s disease over the course of the longitudinal study. Such evidence would suggest a causal relationship under which practicing a musical instrument, as defined by the parameters put forth in this study, is protective against AD diagnosis.
Part 4
Part 5
Alzheimer’s disease (AD) is a neurodegenerative disorder that degrades brain functions like planning, memory, and mood regulation. It is particularly common in elderly people, with 5.3 million Americans over the age of 65 currently affected (Alzheimer’s Association, 2017). Given its pervasiveness, one natural question to ask is what factors cause a person to get AD. In fact, studies show that both genetics and environment play a role in the likelihood of getting AD, with genetics playing a slightly larger role than environment (Gatz et al., 2006).
Given this distribution between genetic and environmental influences, a lot of research has gone into understanding which environmental factors are most important in preventing AD. Some environmental factors which are thought to be potentially important include a person’s diet, exercise regime, and education level (Adlard et al., 2005; Evans et al., 1997; Scarmeas et al., 2006). One environmental factor that may be manipulated to prevent AD onset is playing a musical instrument; one study found an association between playing a musical instrument in older age and a lower likelihood of AD diagnosis (Balbag et al., 2014). However, although this study established a correlation between playing a musical instrument and a lower likelihood of AD, it did not establish that playing a musical instrument causes individuals to evade AD diagnoses. With that said, playing a musical instrument is an appealing mode of treatment on the surface: it is non-invasive and modifiable based on the patient (Balbag et al., 2014). But is it effective as a treatment? The results presented here look promising: the present study establishes a causal relationship between playing a musical instrument and preventing AD diagnosis.
This study used a longitudinal design to test the causality between playing a musical instrument and protecting against AD. Ten thousand pairs of monozygotic twins between the ages of 60 and 65 participated in this study. Both twins in all twin pairs began the study with no significant musical experience or training. One twin in each twin pair was randomly assigned to one of two conditions. In the Non-Musician Condition, participants continued living without musical experience or practice, while participants in the Musician Condition were assigned to practice a musical instrument for an hour on two or three days per week. Each year, participants were screened for AD using a previously-established set of criteria from the National Institute of Neurological and Communicative Disorders and Stroke and Alzheimer’s disease and Related Disorders Association (NINCDS-ADRDA) (McKhann et al., 2011).
The results of this study find that a lower percentage of participants who played a musical instrument were diagnosed with AD over time as compared to participants who did not play a musical instrument. Such results suggest that playing a musical instrument does have a causal effect in mitigating AD diagnoses. All in all, these results should be used to form policy that supports older adults in continuing to play music to help prevent AD diagnoses.