Osteoporosis and osteopenia are chronic skeletal conditions characterized by low bone density and microarchitectural deterioration of bone tissue [1] [2] [3] . With ageing, enhanced resorption and decreased bone formation occurs leading to a net loss of bone mass and ultimately risk of osteoporosis and osteopenia [4] . The World Health Organization (WHO), the International Osteoporosis Foundation (IOF) and bone health research literature, identify a number of non-modifiable and modifiable risk factors associated with the development of osteoporosis and osteopenia. Non-modifiable risks include female gender, increased age, family history of osteoporosis, and being Caucasian. Late menarche, early menopause and low endogenous estrogen levels are also associated with low bone mineral density [1] [2] [5] [6] . Modifiable risks include sedentary lifestyle, smoking, poor dietary habits, lack of sunlight and estrogen deficiency. Certain medications are also indicated as risk factors for example anticonvulsants and glucocorticoids [7] . Higher prevalence of risk factors has been shown to lead to both a higher potential of fractures and higher rates of morbidity with devastating consequences for independence, quality of life and overall health and well-being [5] [8] .

Osteoporosis and osteopenia have been widely investigated in the general population [5] [9] [10] , however relatively under investigated among people with intellectual disability (ID), and especially among people with Down syndrome (DS) [11] - [16] .

Down syndrome (DS) is one of the most commonly known genetic causes of ID and its pathogenesis are well documented [17] . Increased life expectancy is unmistakable among people with DS [18] prompting an increased risk to older age health conditions such as osteoporosis. People with DS are specifically vulnerable to musculoskeletal disorders and are more likely to have infrequent health checks or routine screening [19] .

Prevalent features among people with DS contributing to osteoporosis include low estrogen levels, late menarche and early menopause in females as well as hypogonadism in males [20] [21] . Increased ageing and early onset of ageing related decline add further burden [22] [23] [24] . Thyroid dysfunction is commonly identified among people with DS, with hypothyroidism the most common presentation [25] [26] impacting significantly on skeletal health and later life osteoporosis [27] [28] . As people with DS age the prevalence of Alzheimer dementia and associated epilepsy increases [29] . Alzheimer’s disease and epilepsy do not directly affect bone status but the subsequent anticonvulsant medications (AEDs) contribute to disruption of bone formation and remodeling especially second generation anticonvulsants [7] . Increased risk of falls, both as a consequence of and a contributor to reduced bone health are also associated with Alzheimer’s disease and epilepsy. However, Torr, Strydom [30] , in their review warn that decline in adults with DS should not be assumed to be associated with Alzheimer’s dementia as functional decline may be as a consequences of a number of underlying conditions especially sensory and musculoskeletal impairment.

Physical activity benefits bone mass, stability, balance and contributes to improved quality of life [31] [32] however physical activity levels at rate to accrue health benefit is low among those with DS [33] . Further, the prevalence of overweight and obesity has been noted at higher levels among people with DS than the general population [34] [35] . Obesity has a cumulative effect on bone health due to the retention of vitamin D by the increased adipose tissue, therefore making it less available for bone metabolism [36] as well as the extra loading on bones and joints increasing the likelihood of falls and possible fracture [37] . Obesity may also be a reflection of imbalanced or poor dietary habits. Known secondary causes of low bone mineral density include poor nutrition and gastrointestinal conditions such as coeliac disease, gastro-reflux disease, and chronic constipation, all highly prevalent among adults with ID and DS [38] [39] . Poor dietary habit, gastrointestinal conditions along with low solar exposure impacts on vitamin D and dietary mineral absorption resulting in an adverse impact on overall bone health [40] .

People with DS have a higher level of health need and experience greater health inequalities in comparison to the general population [41] . Health screening and the identification of specific risks for osteoporosis, prevalent among this cohort, are sparsely investigated and subsequently morbidities can go undetected [42] . Bone health screening is often overlooked [11] [43] . However with no consistent approach to bone screening, evident increased burden of risk factors for osteoporosis yet no clear guidance of the risk burden among people with DS, further investigation is required. Therefore the aim of this paper is to examine the prevalence of risk factors predisposing people with DS to osteoporosis and the relationship of those identified risks to a reported doctor’s diagnosis of osteoporosis.

The data for this paper was drawn from The Intellectual Disability Supplement to The Irish Longitudinal Study on Ageing (IDS-TILDA) which is a national longitudinal study on aging and intellectual disability. The study commenced in 2009 exploring a number of health, social and life domains of older adults with ID over time (for further information see reference [44] ). Data is collected every 3 years and the data presented here is from the first wave of the study.

As may be seen in Table 3, there were more females than males at 56% (n = 83) vs 44% (n = 62) respectively. Their ages were predominantly below 65 years, with 3 participants aged 64 years, all of whom were female. Participants lived in a variety of settings, community group home being the largest (42.9%, n = 63) followed by residential type setting (37.4%). The majority of participants (70%, n = 95) were within the mild to moderate range of ID. A large number of the cohort had no formal education (28.6%, n = 42) with just 39.5% (n = 58) reporting they attained some primary education. Whilst the vast majority visited their General Practitioner (GP) regularly very few used specialist services such as endocrinology (2.7%) or geriatrics (1.4%).

As was previously noted, DS in itself has been shown to be a risk factor for the presence of osteoporosis and osteopenia [11] [15] [16] [47] [48] [49] . Findings here concur that people with DS are a high “at risk” group. The confirmed prevalence of thyroid disease, early menopause, specific medications that interfere with bone metabolism, and levels of inactivity and sedentary lifestyle, all culminate in increased likelihood of developing osteoporosis or osteopenia.

Osteoporosis is receptive to treatment and preventable; however in this study active health promotion was not evident. For example, physical activity engagement at levels that would accrue health benefit was not evident. Although rates of physical activity were very low, some participation is better than none and promoting engagement in exercise that is fun, enjoyable and diverse needs to be encouraged. With imagination and resourcefulness people with DS can be encouraged to engage, however as Heller and colleagues indicate [50] , it is their carers and supporters that make the difference and lead by example.

Attendance at specialists such as an endocrinologist was also low, and although people attended their GP regularly the levels of calcium and vitamin D supplementation was low. In Ireland, a northern hemisphere country, it is acknowledged that sunlight levels are considered low and supplementation is suggested [8] . Genant and colleagues advised that further pharmacological interventions ought to be targeted at those with highest risk of fracture but little evidence of this was found for people with DS [8] . The findings that overall dietary balance in the sample was poor, suggests future research ought to examine whether dietary status is an issue of poor choices or a lack of awareness among health professionals and carers. Considering that many of the participants in the study lived in supported settings, either community group homes or residential settings, where the daily dietary decision making may be taken out of their hands, these findings support the implementation of education to improve overall diet and consideration for supplementation for people with DS.

Levels of diagnosed osteoporosis were not particularly high, but low screening rates with high presence of risk factors perhaps suggest hidden undiagnosed disease, especially among males. No male reported the presence of osteoporosis or osteopenia nor having had a DXA despite risk factors including the prevalence of hypogonadism among men with DS. In addition 13.4% of the participants in this study reported having experienced a fracture with hip fractures occurring at twice the rate reported by those in the general population study The Irish Longitudinal Study on Ageing Wave 1 results (TILDA) [51] ; yet only 8% reported having had a DXA scan. Overall the attendance for DXA is concerning and perhaps a possible explanation maybe that people with DS are fearful of engaging and therefore non-compliant, may have physical deformities that prevents appropriate positioning in the scanner or it may simply be a case where the carer is not aware of the risks people with DS face. Consideration ought to be given to the, Van Allen and colleagues [52] suggestion, and endorsed by Carfi and colleagues [16] of regular systematic screening for people with DS especially as the WHO also recommends such screening for all individuals with one or more strong risk factors. They would argue menopause is one such factor, and as can be seen here, a large number of the women had gone through menopause, and, perhaps hypogonadism among males could be another. Whilst they do concede that population screening is not a cost effective approach, making more widely available techniques such as quantitative ultrasound ought to be explored [8] . The TILDA study included bone screening for general population participants, however confirmation of the doctor’s diagnosis of osteoporosis was much less than numbers found to meet criteria through screening. In the TILDA study they found that 86% (n = 1365) with objectively measured evidence of osteopenia and 72% (n = 218) osteoporosis did not have a doctor’s confirmation of diagnosis [53] . Overall greater surveillance of health risks is seen as a way to improve the health status of older adults with ID [54] .

It must be highlighted that people with DS do experience communication challenges and expressing their health needs can often pose challenges. However, as people with DS age their increased vulnerability to the development of Alzheimer’s dementia is well recognized and perhaps a contributing factor to other clinical signs and symptoms of underlying medical conditions going unrecognized [55] . Alzheimer’s dementia also increases the person’s susceptibility to falling thus increasing the risk of fracture. Instigating measures to prevent and address osteoporosis at an early stage would be preferable, along with increasing carer’s awareness of the potential and insidious nature of osteoporosis along with its disagreeable consequences.

Limitations to this paper must be recognized; the group studied is larger than most published papers on DS and were drawn from a representative sample of people with ID but there were small numbers in some of the subgroups considered. Further, the presence of osteoporosis was based on a doctor’s reported diagnosis and was not objectively measured however future waves are addressing this concern.

Evidence emerges from this study that identified risks which include thyroid disease, epilepsy and its associated medications, inactivity and dietary imbalance are at levels which, based on prior general and DS population studies, would increase the risk of developing osteoporosis. Coupled with the predisposition that already exists among people with DS this is a recipe for future deleterious consequences. Considering prior reports of differences between self-reported and objectively measured osteoporosis, the high prevalence of risk factors among people with DS found here supports further objective investigation of symptoms, and rigorous risk surveillance along with support and encouragement to strengthen positive behaviours such as increased participation in physical activities, to contribute to the promotion of good bone health.

The authors would like to thank the people with intellectual disability who participated in this study, their families, carers, the services involved, the IDS-TILDA Scientific Advisory Committee and the Intellectual Disability Consultative Groups for their support. The authors would also like to acknowledge funding for the IDS-TILDA study from the Health Research Board and the Department of Health. The views expressed are those of the authors and are not necessarily those of the Department of Health, The Health Research Board or Trinity College Dublin. This research was funded by the Department of Health in Ireland and managed by the Health Research Board. The funding bodies did not play a role in the study design or writing of the manuscript.

The authors declare no conflicts of interest regarding the publication of this paper.

Burke, É.A., Carroll, R., O’Dwyer, M., Walsh, J.B., McCallion, P. and McCarron, M. (2018) Osteoporosis and People with Down Syndrome: A Preliminary Descriptive Examination of the Intellectual Disability Supplement to the Irish Longitudinal Study on Ageing Wave 1 Results. Health, 10, 1233-1249. https://doi.org/10.4236/health.2018.109095