Cognitive function/ decline is influenced by age, educational attainment and genetic factors like APOE. Stress might also have a role to play in these changes. Activation of HPA axis and subsequent increase in glucocorticoids may initiate changes in hippocampus and other areas . Social stress ( a broad term encompassing both external emotion-provoking stressors (stressful life events) and internal responses (perception and adaptation) to a given stimulus) is shown to have both positive and negative effects on cognition.Ongoing high-stress level may impair working memory where as moderate/ acute stress can enhance some cognitive functions. For example: Rosnick et al showed that individuals who had experienced the injury or illness of a friend performed better in episodic memory, attention and psychomotor speed tasks. A Swedish study in an older population (Grimby & Berg, 1995) revealed that cognitive decline occurred regardless of stressful life experiences. Literature is inconclusive on the effects of stress.Differences in study design ( cross sectional may not be best suited), stress measures (events or perceived stress) and support available etc might be contributing to this inconsistency.
Y. Leng and colleagues from UK (Cambridge and Newcastle Universities) studied both objective and subjective measures of social stress and cognitive function in a middle- to older-aged English sample ( 5129 participants ) using data from the European Prospective Investigation of Cancer (EPIC)-Norfolk prospective cohort study.
Cohort: In the 5 yrs preceding assessment, half of the participants reported no life events. 18% had atleast one longterm difficulty in that period. Those who have achieved lower educational levels reported significantly higher stress levels and more long-term difficulties. Participants with low MMSE scores were older, more likely to be women and to have come from a lower social class, and to have achieved a lower educational leve
Those who reported slower adaptation to life events were more likely to have lower cognitive function, but the association was attenuated when adjusted for physical health conditions.Higher perceived stress was associated with lower cognitive function and this remained significant after adjustment for all factors.This association was particularly noted among less educated. These differences in cognitive function seemed to be restricted to individuals who reported extreme levels of stress. None of the objective measures of stress in this study were associated with cognitive function.
Limitations: The assessment of psychosocial factors preceded the cognitive assessments by a median of 10.5 years. Base line cognitive functions were not measured and hence the question whether stress is a risk factor for poor cognition or is it an early marker cannot be answered. MMSE has limitations ( eg lack of sensitivity for detecting mild cognitive impairment ).
Conclusions: This is the largest study on the association between stress and cognitive function and the findings are consistent with observational epidemiological studies, where self-perceived stress was found to be associated with cognitive impairment.
Summary of the article:
The association between social stress and global cognitive function in a population-based study: the European ProspectiveInvestigation into Cancer (EPIC)-Norfolk study.Leng Y, Wainwright NW, Hayat S, Stephan BC, Matthews FE, Luben R, Surtees PG, Khaw KT, Brayne C.
Psychol Med. 2013 Mar;43(3):655-66.