The pace of aging varies to some degree between individuals, largely a result of differences in lifestyle and choice. Genetics only begins to significantly influence the outcome at a very late age, and by that time it becomes a question of resilience to high levels of molecular damage. Between 60 and 80, the span of time in which age-related diseases become very prevalent given today's state of medical science, it is the case that very few people can claim genetics to have a significant contribution to their present state of health.
Of the unifying mechanisms one can invoke to explain links between lifestyle and pace of aging, chronic inflammation and raised blood pressure are two of the obvious choices. These two contribute in some way to all of the common age-related conditions, directly or indirectly. So when faced with an epidemiological study that shows a broad correlation between existing osteoporosis and risk of later dementia, chronic inflammation is the obvious candidate. There is plenty of evidence for it to contribute to both disruption of bone maintenance and the progression of neurodegeneration, and lifestyle choices such as exercise and weight gain both strongly influence the state of chronic inflammation in later life.
"There is big interest in the relationship between osteoporosis and dementia. This study is the first to address this question in a very large database enabling the case-control-comparison between patients with and without osteoporosis." This retrospective cohort study used data from the Disease Analyzer database (IQVIA), which compiles information on drug prescriptions, diagnoses, and demographic data obtained directly and in anonymous format from computer systems used by general practitioners and specialists. This database has already been used in several studies focusing on osteoporosis and dementia in recent years.
The study included patients diagnosed with osteoporosis between January 1993 and December 2012 (index date) and were followed for up to 20 years. After applying similar inclusion criteria, controls were matched (1:1) to osteoporosis patients using propensity scores based on age, gender, index year, several comorbidities, and co-therapies. The main outcome of the study was to determine the proportion of patients with all-cause-dementia diagnoses within 20 years of the index date.
The study included 29,983 patients with osteoporosis and 29,983 controls without osteoporosis. After 20 years of follow-up, 20.5% of women with osteoporosis and 16.4% of controls had been diagnosed with dementia. At the end of the follow-up period, dementia was found in 22.0% of men previously diagnosed with osteoporosis and 14.9% of men without this chronic condition. Osteoporosis was associated with a 1.2-fold increase in the risk of being diagnosed with dementia in women and a 1.3-fold increase in the risk of being diagnosed with dementia in men.
"The major hypothesis to explain the association between osteoporosis and dementia is that these two conditions have similar risk factors. These factors include APOE4 allele of the apolipoprotein E, a major cholesterol carrier, lower vitamin K levels, vitamin D deficiency, but also androgens and estrogens." The main limitations of the study are missing data on bone mineral density and on lifestyle-related risk factors (e.g., smoking, alcohol, and physical activity).