This study investigates from an evolutionary psychological perspective the relation between sleep quality and the type of living environment of 146 individuals from Transylvania (Romania). One of the main assumptions in Evolutionary Psychology is that the living conditions of people nowadays differ from the conditions experienced by our ancestors during the evolution of human species, i.e. the Environment of Evolutionary Adaptiveness (EEA; Hagen, 2006). This environmental dissimilarity might have contributed to the development of several pathologies, including sleep disorders. Nowadays, such an environmental dissimilarity can be found between the rural and urban areas in several countries, including Romania. In the light of this assumption, we performed an exploratory study, in which the Pittsburgh Sleep Quality Index (PSQI) was used to measure the subjective sleep quality of Romanian people inhabiting the rural environment (N=53) and of people inhabiting the urban environment (N=93). In average, the Romanian individuals reported a bad quality of sleep (i.e., average Global PSQI score > 5), regardless of the type of living environment. Several significant differences were found between the sleep quality measurements of the inhabitants of the rural and urban environments, such as Sleep Latency (rural > urban), Sleep Disturbancies (rural > urban) and Daytime Dysfunction (rural < urban).
KEYWORDS: subjective sleep quality, environment of evolutionary adaptiveness, daytime dysfunction.
Over the last decade, the attempts of explaining mental disorders from an evolutionary psychological perspective have centered on the possible functions of different medical conditions (Crow, 1991, 1995, 1997; Fiske & Haslam, 1997; Mealey, 2000), as well as on reconsidering the taxonomy of mental disorders (Wakefield, 1997; Wakefield & First, 2003). Thus, a mental disease can be seen either as an evolutionary disfunction (i.e., a failure of natural design), or as a selected condition that might bring advantages on the survival and reproduction of the individuals (Nesse, 2005).
Some authors, such as Nesse (2005), suggest that sleep disorders might have evolved because of the differences between the environmental conditions in which our ancestors lived (Environment of Evolutionary Adaptiveness - EEA; Hagen & Hammerstein, 2006) and the current environment (post-EEA). EEA is not a specific period or a specific place, but a statistical composite of the conditions in which a species has evolved. In other words, EEA refers to a set of selection pressures with whom the ancestors of a species had to cope to during evolution. Pleistocene, the period that began about 2 million years ago and ended about 10000 years ago, is closely associated with EEA for the human species (Hagen & Hammerstein, 2006).
Differences between the conditions of the Environment of Evolutionary Adaptiveness and of the current environment (post-EEA)
In many aspects, the current environmental conditions (post-EEA) are different from those in which the humans have evolved (Heath & Berman, 2008). Such differences include efficient means of transportation from one place to another, automatic tools that can replace and/or optimize physical labor, a constant progression of technologies to improve communications, and numerous other resources that afford a greater level of convenience and efficiency than found in the premodern world. However, these societal and technological advantages have concurrently deprived modern man of exposure to various factors that were present in the evolutionary past, such as normal circadian rhythm and low levels of noise and air pollution. This environmental dissimilarity might affect the individuals' psychological well-being (Buss, 2000; Cosmides & Tooby, 1999; Eaton, Konner, & Shostak, 1988).
For example, in the premodern environment, early man would have likely had a sleep pattern more attuned to the natural circadian rhythms not influenced by artificial light, foods with higher levels of omega-3 fatty acids (Eaton et al. …