There is an increasing amount of evidence that a person’s lifestyle is critical to successful aging. It is hypothesized that ongoing participation in lifestyle activities may confer some resistance to cognitive decline in the older adult. A longitudinal study was recently performed that appeared to consolidate this hypothesis. Small et al. (2011) used data from the Victoria Longitudinal Study that followed approximately five hundred subjects for twelve years. The study authors compared three lifestyle factors with three neuropsychological factors across this time period. The three lifestyle factors were comprised of fitness, cognitive activities and social activities that require “complex cognitive functioning.” The three neuropsychological factors were verbal speed and two types of verbal memory. The study participants varied in age from fifty-five to ninety-four. While the neuropsychological measures were administered by professionals, the lifestyle and health questionnaires depended on the subject’s self-report. This is important to note, since the study lacked an objective assessment of lifestyle or health. Ninety year old test subjects were asked to recall detailed aspects of their health and lifestyle, and the power of the study depended on the accuracy of their self-report.
The study found that preserved verbal speed was associated with preserved physical, cognitive and social activity. The authors discovered that cognition and lifestyle activity were dual coupled. This means that the factors worked both ways. Verbal speed predicted lifestyle activities, and lifestyle activities predicted verbal speed. The results of the memory measures were less coupled than verbal speed. Memory for stories was dual coupled with physical activity, but not cognitive or social activity. For example, increased cognitive activity predicted increased story recall, but the reverse did not hold true. Conversely, better story recall predicted increased social activity, but increased social activity was not associated with better story recall. Memory for word lists was not correlated with physical activity, whatsoever. Increased cognitive activity was predictive of better word list recall, and proficient word recall was predictive of increased social activity, but the reverse did not hold true for either. Generally, the study authors discovered that a decline in cognitive ability preceded a decrease in social activity. This artifact is the opposite of many studies that have demonstrated increased levels of lifestyle activity improving overall cognitive performance. The current authors suggest that impaired cognition causes decreased lifestyle activity, rather than decreased lifestyle activity producing the decline in mental functioning.
As mentioned, it is important to consider the affect of self-report in this study. Both health and overall activity level were measured by self-report of the participants. It is also important to consider that most older adults are not proficient at reciting their medical history, and very few can list their medications accurately. Do not forget the natural tendency for people to please the examiner. Questionnaires completed by test subjects invariably reveal the nature of the study; at the very least there are clues to the desired response. Additionally, accurate self-appraisal declines over time. The self-awareness of a fifty-five year old person is generally greater than an eighty year old. For example, an eighty year old test subject is more apt to make temporal errors than a fifty-five year old subject. Combined with the natural tendency to please the examiner, the eighty year old is likely to report more social and physical activity than they actually experience. The current study may actually have measured the change in self-awareness with age, rather than the influence of lifestyle activity levels on cognitive performance. Since the variable of self-awareness was not controlled in the study, the ability to draw a conclusion was tarnished.
The reader needs to be rather sophisticated and thorough when interpreting scientific articles. The objections to the current study do not invalidate the results. The reliance on self-report reduces the study’s power to predict whether lifestyle affects cognition or cognition influences lifestyle. As with most psychological phenomenon, there is a dynamic interplay between overall lifestyle activity and cognitive functioning. The early onset of Alzheimer’s Disease directly lowers the social interest of the afflicted. Reducing environmental stimulation, at any age, will have negative affects on cognition. It is not surprising that isolating one component of the interaction collapses the dynamic interplay. Statistics is limited in this way, as one variable is examined while others are considered invariable, or held as invariable for purpose(s) of the study. Lifestyle and cognition possess so many variables that an immense effort must be made to reduce the uncontrolled factors. If the study authors used an informant to crosscheck health and lifestyle data, the predictive power of the study would be much greater. Commonly, the cost in money and time becomes prohibitive. The current study used data obtained over a twelve year period, such that informants had to be utilized at the inception of the research. To add the use of informants later in the study would produce two studies, and the data cannot be compared once the methodology is changed. Keep in mind that there is no such thing as the perfect study. The most important part of a research article is not the results, but the limitations that influence the results.