In the present cohort study of over 400 participants randomly selected from a rural Japanese town registry, spinal imbalance in the form of sagittal anteriorization indicated cognitive decline. We observed that MCI could be reliably detected by combining age and the degree of spinal imbalance. Men with SVA ≥ 100 mm at any age, SVA ≥ 90 mm at ≥ 70 years, and SVA ≥ 70 mm at ≥ 80 years were all likely to have MCI. Women with SVA ≥ 70 mm were also likely to have MCI irrespectively of age.
Impaired walking, standing, and standing balance have been related to elevated SVA, 9 and previous studies showed SVA to be correlated with balance ability. 10,11 Diminished walking, standing, and balance have been associated with poor cognitive function in older people as well. 12 Therefore, we hypothesized that spinal imbalance might not only indicate poor motor function, but also reduced cognitive ability.
Also termed pre-dementia, MCI is common in older people, and its frequency is rising in aged and super-aged societies. 13 MCI includes problems with memory, language, thinking, and judgment but does not comprise dementia; thus, some cases of MCI do not deteriorate further. In individuals over the age of 70 years, 14% have sufficient cognitive impairment to warrant a diagnosis of dementia. 14 Gait slowing is common among patients with this condition. 15,16,17 In the Obuse study cohort, the prevalence rate of MCI reached more than half among participants in their 70's and over 80% among those in their 80's.
ASD and frailty are closely and interactively related. 18 Patients with ASD cannot exercise muscular strength sufficiently and often exhibit symptoms of intermittent claudication due to back pain. 19 Pressure on the abdomen may also cause losses in appetite and weight and contribute to frailty. Frailty is a pre-disease condition comprehensively summarizing the symptoms accompanying aging and includes the concept of a decline in social activity due to mental and physical changes. Although frailty is reversible, the patient’s ASD may deteriorate permanently in severe cases.
On the other hand, spinal alignment changes less severe than those in ASD are not included in frailty. Such alterations tend to be regarded as a natural consequence of age. However, MCI with spinal alignment changes may be a factor contributing to frailty through mental and social decline. On report found an association between severe kyphosis patients and diminished health-related QOL. 20 Although it remains difficult to prove a direct causal relationship between postural changes and MCI, our results demonstrate that spinal anteriorization and MCI are correlated phenomena occurring simultaneously with age. Thus, when visible appearance changes in posture occur, appropriate diagnostic measures are advised in consideration of the possibility of cognitive impairment to help prevent frailty, dementia, and bedridden status.
The limitations of the current investigation include a cross-sectional design and the possibility of selection bias. First, since this was a cross-sectional study, the causal relationship between sagittal spinal balance and cognitive function could not be established. Cognitive function is influenced by numerous direct factors which include genetic, health, and environmental sources. Due to the multifactorial nature of cognitive function, the present study investigating indirect factor (i.e., sagittal spinal alignment) associations should have ideally considered more possible confounders. However, it was not possible to completely account for the myriad of relevant factors, especially potential ones, and longitudinal studies using this investigation as a prelude are being planned. Furthermore, sagittal spinal alignment is also considerably influenced by numerous factors, such as age, lifestyle, disability of physical activities, osteoporosis, degenerative joint disease, spinal disease including lumbar stenosis and degenerative sagittal imbalance, and pain; even in the same person, sagittal spinal alignment may change daily according to his or her physical condition. As this study merely presents correlations, longitudinal research is necessary to exclude the effects of relevant confounders and address the basis of the association, including causal relationships. Second, since this was a non-compulsory survey, the proportion of randomly sampled people who ultimately participated in the survey was less than half, implying incomplete selection bias elimination. Nevertheless, the Obuse study cohort closely resembled the average Japanese population due to its distinctive survey design. In order to maintain ADL, IADL, and QOL in older people, it will be necessary to monitor for signs of impending cognitive impairment that may lead to frailty and dementia. Our results showed that the anteriorization of spinal balance existed at the onset of cognitive impairment. Accordingly, greater attention is warranted to changes in posture among community-dwelling older people. Lastly, potential human error in the measurement of radiographic angles is an important limitation that must be mentioned. Advanced evaluation techniques, such as the use of machine learning, are being considered to improve the accuracy and reliability of measurements for future work.
In conclusion, spinal balance anteriorization was significantly associated with cognitive function decline in Japanese older adults. MCI could be reliably detected by combining age and the degree of spinal imbalance. Men with SVA ≥ 100 mm at any age, SVA ≥ 90 mm at ≥ 70 years, and SVA ≥ 70 mm at ≥ 80 years are likely to have MCI, while women with SVA ≥ 70 mm at any age are likely to harbor this condition. Such visible clues as the anteriorization of spinal balance can help to more easily monitor for signs of impending cognitive impairment, which may lead to dementia and frailty.