Declining visual capacities in older adults have been posited as a driving force behind adult age differences in higher-order cognitive functions (e.g., the "common cause" hypothesis of Lindenberger & Baltes, 1994, Psychology and Aging, 9, 339-355).
An alternative hypothesis would be that a strong genetic structure for LC T*Pwas already present during the Mesolithic Era and lead to differential milk consumption in European populations ("The reverse cause hypothesis" [9], [27]).
These observations in mice have led our group to develop a common cause hypothesis that asserts that misexpression of PTP1B, and potentially of other genes causing defects in breast development, may not only cause difficulties in breastfeeding but could also lead to increased risk for breast tumour formation and cancer progression.
The common cause hypothesis [ 119] proposes that a general reduction in processing efficiency drives both phenomena.
The common cause hypothesis postulates that there are core common underlying processes which drive ageing throughout the human body.
Further, the common cause hypothesis explains the age-related differences in sensory and cognitive function as the outcome of degenerative processes in neural structures.
This finding supports the common cause hypothesis, by demonstrating that the rate of sarcopenia and ARCD may occur in parallel within individuals, driven by core underlying biological processes.
If we are able to demonstrate an association between muscle size and brain size and function, this could add further weight to the common cause hypothesis [ 34- 37].
Other potential explanations for the empirically observed co-variation in hearing and cognitive function [ 11, 12] include (1) the common cause hypothesis [ 10, 41] and (2) accumulated impairment hypothesis.
In the present paper, the relationship between hearing loss and cognitive functioning was different across the types of language tests employed and between the predementia and dementia groups, thus the results do not support the common cause hypothesis.
