The team said the high numbers of vitamin D deficiency meant more awareness and better public health strategies are needed to achieve optimum vitamin D levels to support healthy ageing.
“Our study identified factors associated with vitamin D deficiency, including being aged 80+ years, obesity and sedentary lifestyles; all of which are increasing traits in western populations,” said associate professor in Nutrition at Trinity College Dublin, Maria O'Sullivan.
“Furthermore, this is one of the few studies to highlight the importance of non-white ethnicity in vitamin D deficiency in a large study of ageing. The findings are valuable in developing targeted strategies to eliminate vitamin D deficiency (at 30 nanomols per litre (nmol/L)) in older populations.”
A number of age-related conditions, such as bone loss, fracture risk, and falls, are linked to low levels of vitamin D and its metabolites.
Further evidence exists for its non-skeletal roles in immune function, cardiovascular disease, dementia, and all-cause mortality.
Vitamin D deficiency in older populations vary across Europe and the UK, with studies varying between 0–77%.
While evidence supports the effectiveness of vitamin D food fortification the uptake of both fortified foods and vitamin D containing supplements remains low in older adults in the UK.
IOM and ES standards
This study enrolled 6004 adults, aged over 50 years in which vitamin D deficiency was categorised by two criteria: Institute of Medicine (IOM) (less than 30 nmol/L) and Endocrine Society (ES) (less than 50 nmol/L).
The overall prevalence of Institute of Medicine (IOM) and Endocrine Society (ES) definitions of deficiency were 26.4% and 58.7%, respectively.
The team found those more likely to be vitamin D deficient (by IOM) were females, aged 80 and over, who smoke, are of non-white ethnicity, are obese and of poor self-reported health.
Further results revealed that residents in the south of England had a reduced risk of deficiency even after adjustment for socioeconomic and traditional predictors (obesity, age, lifestyle, etc) of vitamin D status.
Other factors, such as being retired, having a normal BMI, engaging in regular vigorous physical activity, vitamin D supplement use, sun travel, and summer season were also significantly positive correlates of deficiency.
Comparable results were noted for the ES cut-off definition, where more than half of adults aged over 50 years had 25(OH)D (vit D metabolite) concentrations less than 50 nmol/L.
“Those who used a vitamin D supplement, were less likely to be vitamin D deficient as may be expected,” said study team member Dr Niamh Aspell
“However, supplement use was low (4.4%) and, therefore, food fortification and other strategies need to be considered at policy level for older populations.”
In discussing the findings’ significance, the team identified a distinct north-south difference in deficiency and in 25(OH)D concentrations, with those residing in the south of England identified as less likely to be vitamin D deficient.
The team said latitude contributed significantly to 25(OH)D concentration, even within a country of such a short ranging latitude, with each 1° northerly increase associated with an 11% increased risk of vitamin D deficiency.
Interestingly, even though London is located in the South of England, the study found high levels of vitamin D deficiency.
The team thought this may reflect urban lifestyles, the heterogeneous population (with extremes of affluence and poverty), or population aggregation, where more people with chronic conditions may aggregate in cities.
They also noted that currently, the UK does not have a mandatory vitamin D food fortification policy, which could be contributing to the high levels of deficiency observed throughout the country.
"The high rates of deficiency are similar to rates seen in other high latitude countries such as Ireland," said co-author and Trinity research fellow Dr Eamon Laird. "However, other more northern countries such as Finland have implemented a successful vitamin D fortification policy which has all but eliminated deficiency in the population. Such a policy could easily be implemented in the UK and Ireland."
Published online: doi.org/10.3390/nu11061253
“The Prevalence and Determinants of Vitamin D Status in Community-Dwelling Older Adults: Results from the English Longitudinal Study of Ageing (ELSA)”
Authors: Niamh Aspell et al