Current study examined 25(OH)-D levels to determine the prevalence of vitamin D deficiency or insufficiency and also studied selected associated factors among post-menopausal women with suspected osteoporosis. Bone density assessment was carried out among 77participants. To the best of our knowledge, this is the first study in our region examined vitamin D status among post-menopausal women even though several studies examined vitamin D level in general population. Gunawardane et.al found that Vitamin D deficiency was 57.2% (< 20 ng/ml), vitamin D insufficiency 31%(20–30 ng/ml) and the cumulative prevalence of deficiency & insufficiency was 88.2% (11) and high prevalence was found among young adults (age 18 − 14)(4). In the present study, the mean 25(OH)-D concentration was 27.5 ng /ml ± 8.09 ng/mL and 19% (95%CI: 12.4–27.4) had vitamin D deficiency (25(OH)-D concentration < 20 ng/mL). Overall, we have found that cumulative deficiency and in sufficiency of vitamin D was common, 63.8% (95%CI: 54.3–72.6).But a study among 123 postmenopausal women evaluated in Romania reported 91.9% of them had 25OHD serum levels below 30 ng/ml (15) and likewise a study from Pakistan among 200 postmenopausal women presented to Orthopaedics and Gynaecology outpatient departments of Khyber Teaching Hospital showed that prevalence of vitamin D deficiency was 59% and 22% had insufficient levels (10). Almost similar findings revealed in a study from North India which showed vitamin D deficiency among 62% of subjects (16).Even though direct comparison among the these studies is difficult, relatively low prevalence among our sample could be due to a good exposure of sunlight a natural source of vitamin D throughout the year as northern Sri Lanka is located in the middle of the tropical Indian subcontinent. Historically, most of the requirement of vitamin D is from sun light–induced manufacture of cholecalciferol by skin (7). Seventy five of participants (71.4%) reported adequate level of sun exposure (> 30minutes). Authors of the study conducted in Pakistan reported that the use of sun protection, wearing purdah and in general women do not go out of their home were possible explanations for low vitamin D levels in their population(10) however in Sri Lankan culture there is neither observation of purdah nor any cultural restriction for women to go out from their homes to support our findings.
Many studies have showed an increasing level of vitamin D deficiency with age [17, 18]. The main reason would be that the elders would have decreased concentrations of precursor of vitamin D3 (7-dehydrocholesterol) that leads to decreased ability to make vitamin D by skin . However, in the present study, vitamin D level showed positive correlation with advancing age (r-0.225, P-0.021). Again the amount of sun exposure is a possible factor contributed to this findings. Young women tend to spend more time indoors with their occupation while a traditional house wife in Jaffna and the elderly could have spent more time outdoors. This finding was comparable to some previous studies (19, 20) and further a study in Thailand showed young people may use more sunscreen because of cosmetic reasons (19), however this practice was not observed in this study as only two participants (1.9%) reported to use sunscreen. In terms of dietary sources, common non-fortified food sources include breast milk, cod liver oil, Egg yolk, Fish such Mackerel (canned),Salmon (canned),Salmon (fresh, farmed),Salmon (fresh, wild), Sardines (canned) Tuna (canned) cat fish, yogurt, margarine, cereals and mushroom (1,21). Among 105 participants 53% percentage of them consuming milk on average 3 days per week, 76.2% consuming fish on average 2 days per week, 64.8% consuming egg on average 1 day per week. But no significant difference in vitamin d level is observed who consuming above vitamin D rich resources and not consuming. This indicates dietary source plays a pivotal role.
Vitamin D deficiency symptoms are rather nonspecific which include back pain (non-radiating), arthralgia, proximal muscle weakness, headache, fatigue, altered mood, insomnia and hair loss (22, 23). In our study 57.1% postmenopausal women reported bone pain paraesthesia followed by bone pain (55.2%), easy fatigability (54.3%), Malaise (51.4%), muscle cramps (43.8%) and proximal myopathy (40.0%).But there was no statistical significance observed at 5% level when comparing symptoms among groups with vitamin D deficiency and with adequate level of Vitamin D. This could be due to the fact that the symptoms are non-specific and are common in post-menopausal women even without vitamin D efficiency or might also be associated with other age related co morbid conditions such as osteoarthritis. For example among 105 participants 41.9% had osteoarthritis and 3.8% had rheumatoid arthritis. The study also investigated the relationship between vitamin D deficiency and menopausal symptoms and concluded that the data is not supportive of vitamin D status is associated with menopause related symptoms (24).
Vitamin D deficiency reported to be high in prevalence among inpatients with mental illness in previous studies (25,26).Thirty percent of sample had psychiatric conditions and mean vitamin D level (25.63 ng/ml) less among the participants with psychiatric conditions compare to who are not having psychiatric conditions (28.68 ng/ml).But this results not showed statistically significant(P-0.076).
It is well known fact that prevalence of osteoporosis is common among postmenopausal women and several risk factors implicated for this high prevalence including vitamin D deficiency. Falls and risk of fractures well associated with vitamin D deficiency among post-menopausal osteoporosis (5). Out of 105 post-menopausal women suspected with osteoporosis 71 (66.7%) completed bone density assessment and results revealed osteoporosis range was 38% (27.3–49.7) and same amount showed osteopenia range. But Vertebrae T score in osteoporosis range was high 46 (64.8%) and osteopenia range were 24 (33.8%).Present study failed to show association with different categories of t scores with vitamin D deficiency except Vertebral Z score showed a significant correlation with vitamin D level(r-0.252, P-0.034).This results could be due to a small size and this study not designed to show this association (not comparative study).But it is a well-known fact that vitamin D deficiency is more prevalent among post-menopausal women and supplement of vitamin D might prevent of falls and fractures specially with people with osteoporosis(5,27,28).
But the appropriate cut off level to treat vitamin D deficiency or insufficiency is a dilemma (8). But to maintain of minimum required vitamin D level (30 to 32 ng /mL) requires 2,200 to 3,000 IU/d from all available resources including sun exposure, food and supplements(29,30,31).Further age specific recommendations suggest 200 IU of vitamin D daily from birth to age 50, 400 IU/d for age 51 to 70 years, and 600 IU/d for those age 70 years and above (32,33) This recommendation presume that usual sources of vitamin D such as sun exposure and food are not adequate (30,31).It is an observation that vitamin D supplements for all post-menopausal women may leads to hyper vitaminosis. But supplementation with vitamin D for post-menopausal women with vitamin deficiency is beneficial in preventing osteoporosis especially to prevent complications of fall and fracture (11, 15).Since high prevalence of vitamin D deficiency among post-menopausal women with suspected osteoporosis shown by this study, it emphasize the fact that early screening for suboptimal vitamin D level among the above group is crucial to prevent osteoporotic fractures and falls.
The strengths of this study are that this is the first study in Sri Lanka specifically examined the prevalence vitamin D deficiency among post-menopausal women with suspected osteoporosis and explored some protective factors like sun exposure. Vitamin D level measured by immuno histochemistry method which quoted as standard method. However, some limitations of the study includes that we did not obtain information about some anthropological measurements such as BMI; physical activity; socioeconomic status and the influence of seasonal effects and climatic changes on vitamin D deficiency. Also sample size estimated only with the aim of estimating prevalence but validity of the study would have been improved if we had an estimated sample size for sub analysis. Some participants (33.3%) did not complete bone density assessments which could be the reason for some factors not showed statistically significant association even though some relationship observed in psychiatric condition, sun exposure, z/t scores of vertebrae and vitamin D level.