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Vitamin D status and sun exposure in southeast Asia

Hataikarn Nimitphong^{1 ,}^* and Michael F. Holick²

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Prevalence of Vitamin D Deficiency in Asia

Vitamin D plays an important role in bone metabolism and maintaining bone health and muscle function.¹Vitamin D inadequacy is a worldwide problem and affects developed as well as developing countries, subtropical and temperate regions, and populations of all ages.² Vitamin D deficiency may be overlooked in Asian countries, perhaps on the assumption that vitamin D deficiency is unlikely to occur in regions with plentiful sunshine. This topic aims to review the current evidence about the prevalence of vitamin D deficiency and the sun exposure behavior in Asian populations.

Regardless of the definition of vitamin D deficiency, insufficiency and sufficiency {defined as 25-hydroxyvitamin D [25(OH)D] < 50, 51–74 and > 75 nmol/L, respectively},³^,⁴ studies carried across different countries in South Asia and Southeast Asia revealed widespread prevalence of vitamin D deficiency and insufficiency. In India, located between 8°N-38°N, there is plenty of sunshine all year round and thus people in India should not have and inadequate vitamin D status. On the contrary, epidemiologic studies from different parts in India reported higher than 70% prevalence of vitamin D deficiency [25(OH)D < 50nmol/L] in all age groups, including toddlers, school children, pregnant women and their neonates and adult males.⁵For example, a study in school girls (n = 404, 48% lower socioeconomic strata) in Delhi, located at 28.38 °N, reported 91% were vitamin D deficient.⁶ The prevalence of vitamin D deficiency was similar in both lower and upper socioeconomic strata with the mean 25(OH)D levels of 29 ± 13 and 34 ± 17 nmol/L, respectively(p = ns).⁶ Seventy percent of healthy volunteers (n = 1,137) in Mumbai, the western part of India located at 18.56° N, had vitamin D deficiency [mean 25(OH)D levels = 44 ± 23 nmol/L] with a slightly higher prevalent (79%) in females.⁷

Vitamin D status in Southeast Asian countries has recently received more attention. There were some health examination surveys (n~2,500–7,000) of countries in this region as summarized in Table 1.⁸^-¹⁰ Most studies defined vitamin D deficiency as 25(OH)D levels of < 50 nmol/L. In the Singapore Chinese Health Study (SCHS), 504 middle age and elderly participants (aged 45–74 y, 56% female) were evaluated for the distribution of serum 25(OH)D concentration.¹¹ As Singapore is 1° N, this study population provided a unique opportunity to evaluate the factors associated with vitamin D status in the absence of seasonal variation in UV exposure. The mean 25(OH)D concentration was 69 nmol/L overall, lower in females (64 nmol/L) compared with males (74 nmol/L), p < 0.001. A greater percentage of vitamin D deficiency was also found in females (18% vs. 9%).¹¹ Among these Southeast Asia countries, Thailand had the least prevalence of vitamin D deficiency, possibly related to its geographical location close to the equator.¹⁰ Singapore had slightly higher prevalence of vitamin D deficiency than in Thailand, partly due to being a more industrialized country even though Singapore is located closer to the equator. Overall, the common predictors of having low vitamin D status in this Southeast Asia were younger age, being female, living in an urban area and being less physically active.⁸^-¹¹

Table 1. Summary of prevalence of vitamin D deficiency and its determinants from National population based studies in Southeast Asia

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Sunlight as a Source of Vitamin D: Some Limitation in Asia

For most people, the main source of vitamin D is skin exposure to sunlight. After exposing to UVB (UVB: 290–315 nm), UVB photons causes the photolysis of 7-dehydrocholesterol (7-DHC, provitamin D₃; the immediate precursor in the cholesterol biosynthetic pathway in the skin) to previtamin D₃, which thermally isomerized (37°C) to vitamin D₃ by a membrane enhanced mechanism. Vitamin D₃ is further 25-hydroxylated at the liver to become 25(OH)D₃ and then 1-α-hydroxylated at the kidneys to become active form; 1,25-dihydroxyvitamin D₃[1,25(OH)₂D₃].¹ Many factors reduce the skin’s production of vitamin D₃, including increased skin pigmentation, aging, and the sun protection behaviors such as application of a sunscreen or cover most part of their bodies with clothes.¹²^-¹⁴ An alteration in the zenith angle of the sun caused by a change in latitude, season of the year, or time of day dramatically influences the skin’s production of vitamin D₃.¹²^,¹⁴

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Age and gender

In general, the cutaneous production of vitamin D declines with age.¹⁵^,¹⁶ Aging is associated with decreases the 7-DHC concentration in the skin, resulting reduction by more than 4-fold vitamin D₃ production in a 70-y-old compared with a 20-y-old adult.¹⁵^,¹⁶ In addition, elderly usually stay indoors for prolong periods of time and have limited physical activity due to multiple co-morbidities, which further contribute to less sun exposure. Interestingly, elderly in Southeast Asia such as Thailand¹⁰ and Korea⁹ have a better vitamin D status when compare with younger people. The possible explanation is these elderly have more free time and spend time doing outdoor activities.¹⁰ The rapid economic development over the past decade in many countries of Southeast Asia has resulted in young adults having indoor jobs, while elderly adults tend to have outdoor jobs.⁹ The high prevalence of vitamin D deficiency in young adults, especially in adolescents, raises about a bone health concern in this critical period when they are achieving peak bone mass. Studies finding appropriate strategies to improve vitamin D status in this group of population are urgently wanted.

As in western countries, there is evidence that females in Asian countries have lower 25(OH)D levels than in males.⁸^-¹¹^,¹⁷^,¹⁸ Gender differences occur mainly due to clothing and sun protection behavior in females because of the cosmetic concerns. Fair skin is associated with beauty in these populations. For example, a telephone interview survey of 547 middle-aged and elderly Chinese women living in Hong Kong (an industrialized city situated on the southern coast of China at latitude of 22.5 degrees north) revealed that 62% of respondents did not like going in the sun.¹⁸ As high as 67% and 58% of respondents spent an average of 6–10 h indoors and between 6:30 a.m. and 7:00 p.m. during weekdays and Sundays, respectively. Almost half of the respondents used a parasol to shade themselves from the sun.¹⁸ Muslims, especially in females, traditionally have most part of their body covered when compare with males.¹⁷

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Skin color and culture behavior

Human skin has a huge capacity to produce vitamin D₃. From the experimental data that exposure of the body in a bathing suit (almost 100% of body surface area) to sunlight that causes a minimal erythemal dose (MED) is equivalent to taking between 10,000 and 25,000 IU of vitamin D orally.¹² Therefore, exposure of 6% of the body to 1 MED is equivalent to taking about 600 and 1,000 IU of vitamin D. However, the simplest strategy is “Holick’s rule” which is exposing face, arms and legs for a period equal to 25% of the time that it would take to cause 1 MED for two to three times a week can satisfy the body’s vitamin D requirement while minimizing sun damage.¹² To apply this strategy we need to know MED for each skin type at the specific latitude and time. Generally, exposure of arms and legs for 5 to 30 min (depending on time of day, season, latitude, and skin pigmentation) between the hours of 10 a.m. and 3 p.m. twice a week is often adequate.¹ Comparing to Caucasians (mostly skin type2 or 3), Asians have skin type 4 or 5. Therefore, with the same amount of MED, dark-skin individuals require greater duration of exposure than their light-skinned counterparts to synthesis comparable amount of vitamin D₃.¹⁹ Setiati S et al.,²⁰ conducted a study of sun exposure in elderly women in Jakarta, Indonesia (latitude of 6°S). They did repeated measurement of sun exposure intensity from 7am to 4 p.m. by using UV meter to get the MED/hour. They found that in Jakarta, the highest intensity of UVB occurred at 11 a.m. to 1 p.m. (~2 MED/hour). But for more convenience, they decided to ask subjects (n = 74 elderly women with type-4 skin) to expose to sunlight at 9 a.m. which contained about 0.6 MED/hour by average. According to Holick’s rule, exposing to sunlight at the face and both arms for 25 min, 3 times a week at 9 p.m. should maintain adequate vitamin D status. After exposing to sunlight at this specific time and duration for 6 weeks, mean 25(OH)D levels of participants increased from 59 nmol/L at the baseline to 84 nmol/L.²⁰ One of limitation in this study is that their UV meter detected both UVA and UVB. And in general, MED is not always a marker of vitamin D₃ synthesis in the skin. For example, at the higher-wavelengths UVA radiation can produce skin erythema without any vitamin D synthesis.¹⁹ The sunlight in the early morning and late afternoon contain mostly UVA, not UVB.¹²Nonetheless, this study proved the concept that people with dark skin have ability to achieve sufficient vitamin D status by going to the sun at the proper time with adequate duration of sun exposure.

The variation of vitamin D status in people who live in the same city or country is partly link to religious, lifestyle and nutritional difference. Such as the Thai 4th National Health Examination Survey reported that non-Muslims (~97% of total subjects) had 10 nmol/L higher levels of 25(OH)D when compared with Muslims (80 ± 1 vs. 69 ± 4 nmol/L, respectively).¹⁰ There was a report that only 1/3 of participants were vitamin D sufficient [25(OH)D ≥ 50 nmol/L] in Malaysia which is a tropical country located at the equator and is sunny all year round. Most of the populations are Muslim. It’s not surprise that the lower 25(OH)D levels were found in females, explained by the tradition costume (wearing long sleeves, long skirts and veil).¹⁷ In addition, lower 25(OH)D levels in the urban population were consistently found in almost geographical region of Asia.⁸^-¹⁰^,²¹ Limiting outdoor activity due to urbanization underlie lower vitamin D status. Air pollutants efficiently absorb UVB radiation and thus reduce the amount that reaches the earth’s surface. This phenomenon may partially explain why residents of big cities such as Bangkok (Thailand),¹⁰Delhi (India)²² had the lowest 25(OH)D concentration when compared with other cities/area in those countries. Consuming fatty fishes and sundried mushrooms which are major sources of vitamin D in food might help maintain proper vitamin D status in scanty UVB environments such as in winter. For example, a study of 157 elderly Japanese women in Toyosaka City, Niigata (latitude 38°N) reported that the mean 25(OH)D concentration of woman who consumed ≥ 4 times/week fish was higher by 10 nmol/L than those who consumed fish only of the 1–3 times/week group in winter.²³ However, there was no such finding in their summer study in which demonstrated that sunlight exposure was sufficient.²³

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Latitude and season

Countries near to the equator receive more sunlight all year round compare with those far from the equator. However, sun-seeking behavior is uncommon in these populations because climate is frequently too hot.²Thus, sun protective behaviors; including wearing a hat, applying sunscreen, using an umbrella, wearing long sleeves or staying in the shade, influence on vitamin D status in this sunshine area. It is well established that sunscreens markedly reduce transmission of UVB radiation in to the skin.²⁴ But often inadequately applied may have little impact on vitamin D status. One study in Australia reported that staying in the shade is the most important determinant than other behaviors, including wear a hat, apply sunscreen, use an umbrella and wear long sleeves, of poor vitamin status in these areas.²⁵ However often people do not apply the proper amount of sunscreen which could help explain their observation. When a sunscreen with an SPF of 8 was properly applied to the skin, vitamin D₃ production was reduced by more than 90%.¹³

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Health benefit of sun exposure in Southeast Asia

The health benefit of UVB exposure in population of Southeast Asia is demonstrated as in Caucasian. For example, mortality rates for all cancers and cancers of esophagus, stomach, colon and rectum, liver, lung breast, and bladder were negatively associated with average daily ambient UVB irradiance in 263 countries in China during 1990–1992, a report by Chen W, et al.²⁶ Juzeniene A, et al. reported the correlation between seasonal variations in vitamin D photosynthesis and non-pandemic influenzas in Singapore and Japan.²⁷ A small seasonal variation in influenza has been observed in Singapore, a country which is close to the equator and thus less seasonal variation in vitamin D photosynthesis throughout the year. On the other hand, in subtropical region such as Okinawa, Japan (26 degree north), which the rate of vitamin D photosynthesis in winter is only ¼ of those in the summer, there is a regular, major outbreak of influenza in the winter and a minor outbreak in the summer. This pattern is similar to influenza circulation in other subtropical areas.²⁷

In conclusion, vitamin D deficiency is common in South Asia and Southeast Asia, affecting all age groups. Latitude of the countries as well as attitudes and behavior toward sunlight exposure are the major determinants of vitamin D status in a population where sunshine is abundant. Health benefit of sun exposure in population of Southeast Asia, such as the cancer mortality rate and non-pandemic influenzas incidence, was reported as those observed in population in other part of the world.

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2013 Dec;169(6):1272-8. doi: 10.1111/bjd.12518.

Lifestyle factors including less cutaneous sun exposure contribute to starkly lower vitamin D levels in U.K. South Asians compared with the white population.

Kift R¹, Berry JL, Vail A, Durkin MT, Rhodes LE, Webb AR.

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Abstract

BACKGROUND:

Long-standing concerns over the vitamin D status of South Asian adults in the U.K. require studies using statistically valid sample sizes to measure annual variation and contributory lifestyle factors.

OBJECTIVES:

To measure annual variation in the vitamin D status of U.K. South Asians, to determine the associated lifestyle influences, and to compare these with a similar study of white adults.

METHODS:

A single-centre, prospective cohort study measuring circulating 25-hydroxyvitamin D [25(OH)D], sunlight exposure levels and lifestyle factors for 1 year in 125 ambulant South Asian adults with sun-reactive skin type V, aged 20-60 years, in Greater Manchester, U.K. (53·5°N).

RESULTS:

The 25(OH)D levels of South Asians were alarmingly low. In summer, their median 25(OH)D level was 9·0 ng mL(-1) , [interquartile range (IQR) 6·7-13·1], falling to 5·8 ng mL(-1) (IQR 4·0-8·1) in winter. This compared with values in the white population of 26·2 ng mL(-1) (IQR 19·9-31·5) in summer and 18·9 ng mL(-1) IQR (11·6-23·7) in winter. Median daily dietary vitamin D was lower in South Asians (1·32 μg vs. 3·26 μg for white subjects) and was compounded by low supplement use. Despite similar times spent outdoors, ultraviolet (UV) dosimeters recorded lower personal UV exposure among South Asians, indicating sun avoidance when outside, while sun exposure diaries recorded lower amounts of skin surface exposure.

CONCLUSIONS:

The majority of South Asians never reached sufficiency in vitamin D status. Lifestyle differences, with lower oral intake, sun exposure and rates of cutaneous production due to darker skin, indicate that standard advice on obtaining sufficient vitamin D needs modification for the South Asian community in the U.K.

http://www.ncbi.nlm.nih.gov/pubmed/23364011

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The Epidemiology of Diabetes in Korea

Dae Jung Kim

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INTRODUCTION

Diabetes is an increasing global health problem []. The increased prevalence is likely attributable to rapid economic development, improved living standards, an aging population, and a Westernized lifestyle. Diabetes and its complications have become a major cause of morbidity and mortality in Korea [2]. Although diabetes-related mortality has recently decreased from 25.1 per 100,000 persons in 2002 to 19.6 per 100,000 persons in 2009, diabetes is still the fifth-leading cause of death in Korea [2]. Diabetic complications such as renal failure, neuropathy, retinopathy, coronary and cerebral artery diseases, and amputations are associated with increased medical costs and reduced life expectancy [3].

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PREVALENCE OF DIABETES AND PREDIABETES: A COHORT STUDY

The first epidemiologic study on diabetes was conducted in the rural area of Okku-gun, Chollabuk-do, in 1971 [4]. With the criteria of ≥160 mg/dL for 1-hour glucose and ≥110 mg/dL for 2-hour glucose after a 50 g oral glucose tolerance test (OGTT), the prevalence of diabetes was 0.91% (1.41% of males, 0.42% of females) among the total subjects aged ≥10 years, and 1.5% (2.5% of males, 0.7% of females) among adults aged ≥30 years (Table 1).

Table 1

Prevalence of diabetes and prediabetes among Koreans: the cohort data

In the 1980s, there was a large, healthcare center-based survey on the prevalence of diabetes [5]. After the 50 g OGTT, diabetes was diagnosed with criteria of fasting glucose ≥140 mg/dL and 1-hour glucose ≥200 mg/dL. The prevalence of diabetes among subjects aged ≥10 years was 3.5% (4.2% of males, 2.4% of females). The prevalence of diabetes increased according to age: 2.2%, 0.5%, 0.9%, 3.4%, 7.1%, 10.4%, and 10.7% in the second to eighth decades, respectively. The prevalence of impaired glucose tolerance (IGT) was 8.0%.

In the 1990s, there were many epidemiologic studies on diabetes prevalence. According to the data from the Korea Medical Insurance Corporation (KMIC), which provides insurance to civil servants and private school workers aged 35 to 59, the prevalence of diabetes was defined as a mean fasting blood glucose of ≥126 mg/dL in 1990 to 1992 was 4.7% in men and 1.3% in women []. The prevalence of diabetes in the KMIC cohort may be underestimated because OGTTs were not performed and KMIC workers tend to be healthier than the general population.

A well-designed population-based cohort study was first conducted in Yonchon County in 1993 []. A total of 2,520 participants underwent a standard 75 g OGTT. The prevalence of diabetes was 7.2%, substantially higher than that in the previous study, and the prevalence of IGT was 8.9%.

Another population-based study was performed in Jungup District in 1997 [8]. Among 1,108 subjects who completed the 75 g OGTT, the prevalence of diabetes and IGT as defined by the World Health Organization (WHO) criteria were 7.1% and 8.5%, respectively, after correction for Segi's standard world population. When the 1997 American Diabetes Association (ADA) criteria were employed, the prevalence of diabetes and IGT increased to 8.5% and 11.1%, respectively.

An epidemiologic study of diabetes in Korean urban communities was performed in Mokdong, Seoul, in 1998 [9]. There was an 8.5% prevalence of diabetes and 7.8% prevalence of impaired glucose regulation (IGR), including IGT and impaired fasting glucose (IFG). The age-adjusted prevalence of diabetes and IGR was 8.4% and 7.1%, respectively. Interestingly, the prevalence of diabetes in the urban area was slightly higher than that in the rural area.

The Korea Center for Disease Control designed a prospective, large-scale, community-based cohort study [,]. In a baseline study in 2001 to 2002, the prevalence of diabetes was 12.6%, including 6.0% known diabetes and 6.6% newly diagnosed diabetes. Accordingly, there was a rapid and dramatic increase in diabetes in Korea.

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PREVALENCE OF DIABETES AND PREDIABETES: A NATIONAL SURVEY

With increased attention to social welfare in Korea, the Ministry of Health and Welfare conducted a series of Korea National Health and Nutrition Examination Surveys (KNHANES) to examine the general health and nutrition status of Koreans [].

The prevalence of diabetes among adults aged ≥30 years in 1998, 2001, 2005, and 2007-2009 was 11.1%, 8.9%, 9.1%, and 9.9%, respectively. The proportion of known cases of diabetes drastically increased from 23.2% in 1998 to 41.2% in 2001, 68.0% in 2005 and 72.3% in 2007-2009. The prevalence of IFG also increased from 17.4% in 2005 to 20.4% in 2007-2009 (Table 2).

Table 2

Prevalence of diabetes and IFG among Korean adults: the KNHANES study

Diabetes and IFG increased dramatically with age in 2007-2009 (Table 3, Fig. 1). Among patients 60 years of age or older, the prevalence of diabetes was estimated to be about 20%, and the prevalence of IFG was about 25%. Diabetes and IFG were more frequent in men than in women.

Fig. 1

Prevalence of diabetes and IFG among Korean adults in 2007-2009. DM, diabetes mellitus; IFG, impaired fasting glucose.

Table 3

Prevalence of diabetes and IFG among Korean adults aged ≥30 years in 2007-2009

Therefore, the prevalence of diabetes and IFG in Korea has rapidly increased in the past 40 years from 1.5% to 9.9% for diabetes and 20.4% for IFG (Fig. 2).

Fig. 2

Trend in prevalence of diabetes in Korea. KMIC, Korea Medical Insurance Corporation; KNHANES, Korea National Health and Nutrition Examination Surveys.

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INCIDENCE OF DIABETES AND RISK FACTORS

In the 2-year follow-up study on diabetes in the rural area, the annual age-adjusted incidence of diabetes was 3.2% in men and 1.5% in women []. Another rural cohort revealed that the age- and sex-adjusted incidence rate of diabetes was 16.3 per 1,000 person-years []. The incidence increased as age increased in both sexes. Age, male sex, and fasting and 2-hour glucose levels were significant independent risk factors for the development of diabetes. In the urban area, the age-adjusted annual incidence rate of diabetes for subjects >40 years of age at the baseline was 1.3% [9].

Based on the Task Force Team for Basic Statistical Study of Korean Diabetes Mellitus of the Korean Diabetes Association, the annual incidence of diabetes among Korean adults aged 20 to 79 years was 0.76% (0.73% in men, 0.78% in women) in 2003 [15]. The incidence of diabetes increased with age, but with little difference between men and women. The incidence of diabetes in the 20 to 44, 45 to 54, 55 to 64, and 65 to 79 age groups was 0.26%, 1.19%, 2.04%, and 1.56% in men and 0.18%, 1.04%, 2.09%, and 2.25% in women, respectively.

A recent community cohort study showed that the annual incidence of type 2 diabetes was 1.33% to 2.35% in the 40s, 1.48% to 3.18% in the 50s, 1.85% to 4.55% in the 60s, and 3.08% to 5% in the 70s []. A relatively higher incidence was observed in the urban and male populations compared to the rural and female populations.

According to the follow-up study of women with previous gestational diabetes mellitus (GDM), Korean women with a history of GDM have a 3.5 times greater risk of developing postpartum diabetes than the general population []. Approximately 40% of women with previous GDM were expected to develop diabetes within 5 years postpartum.

IFG is the most important risk factor for diabetes. Based on the prospective cohort subjects with IFG, 16.6% of men and 6.5% of women had diabetes during the 4-year follow-up []. In addition, 21.2% of men and 15.2% of women developed type 2 diabetes in the obese group. Regular exercise is effective in preventing diabetes in people with IFG.

Smoking is an independent risk factor for diabetes [,]. Compared to never-smokers, current smokers had a 1.5- to 1.7-fold increased risk.

Metabolic syndrome, as a clustering of metabolic abnormalities, is also an important risk factor for diabetes. According to the KNHANES cohort, subjects with metabolic syndrome had a 1.3-fold increased risk for diabetes [].

Short sleep duration (≤5 hour) is significantly associated with a 1.2-fold increase in general and abdominal obesity in Korean adults, and is thus associated with increased diabetes [].

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GLOBAL TREND IN DIABETES AND IGT

The International Diabetes Federation provides comprehensive estimates of the absolute numbers and prevalence of diabetes and IGT globally [21]. The total global prevalence of diabetes and IGT in 2010 was estimated at 6.6% and 7.9%, respectively, and is expected to rise to 7.8% and 8.4%, respectively, in 2030 (Table 4). It is estimated that 285 million and 344 million people worldwide will have diabetes and IGT, respectively, in 2010. By 2030, the number of people with diabetes and IGT is projected to increase to 438 million and 472 million, respectively, of the adult population. The largest increases will take place in the regions dominated by developing economies, such as Southeast Asia and the West Pacific region. The prevalence of diabetes and IGT among Korean adults aged 20 to 79 years in 2010 was estimated at 9.0% and 9.4%, respectively, and is expected to rise to 11.4% and 11.5%, respectively, in 2030. The number of Korean people with diabetes and IGT was 3.3 million and 3.4 million, respectively, in 2010, and is expected to increase to 4.3 million and 4.4 million, respectively, in 2030.

Table 4

Estimates of diabetes prevalence in 2010 and 2030

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CONCLUSIONS

Despite much evidence that diabetes can be prevented or delayed with lifestyle changes and weight loss or certain medications, the diabetic epidemic continues worldwide. The largest increases will take place in the developing regions, such as the West Pacific region, including Korea. With increasing obesity, especially in childhood, decreased physical activity, and improved longevity, diabetes and prediabetes is expected to dramatically increase more than previously projected.

Public efforts to introduce healthy lifestyle changes and systematic diabetes prevention programs are necessary to reduce the global epidemic of diabetes.

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ACKNOWLEDGMENTS

This study was supported by a grant from the Korea Health 21 R&D Project, Ministry of Health and Welfare, Republic of Korea (A102065-1011-1070100).

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Footnotes

No potential conflict of interest relevant to this article was reported.

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References

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New study finds autism rates in South Korea now at 1 in 38 children

In the first comprehensive study of autism prevalence using a total population sample, an international team of investigators from the U.S., South Korea, and Canada estimated the prevalence of autism spectrum disorders (ASD) in South Korea to be 2.64%, or approximately 1 in 38 children, and concluded that autism prevalence estimates worldwide may increase when this approach is used to identify children with ASD.

“Prevalence of Autism Spectrum Disorder in a Total Population Sample,” published today online in the American Journal of Psychiatry reports on a study of all children (approximately 55,000) ages 7-12 years in a South Korean community, including those enrolled in special education and the disability registry, as well as all children enrolled in general education schools. Children were systematically assessed using multiple clinical evaluations.

The research by Young Shin Kim, M.D., M.S., M.P.H., Ph.D. of the Yale Child Study Center, and her collaborators Bennett L. Leventhal, M.D., Yun-Joo Koh, Ph.D., Eric Fombonne, M.D., Eugene Laska, Ph.D., Eun-Chung Lim, M.A., Keun-Ah Cheon, M.D., Ph.D., Soo-Jeong Kim, M.D., HyunKyung Lee, M.A., Dong-Ho Song, M.D. and Roy Richard Grinker, Ph.D. found more than two-thirds of ASD cases in the mainstream school population, unrecognized and untreated. “These findings suggest that ASD is under-diagnosed and under-reported and that rigorous screening and comprehensive population studies may be necessary to produce accurate ASD prevalence estimates,” stated Autism Speaks Chief Science Officer Geraldine Dawson, Ph.D. “Autism Speaks funded this study to support better detection, assessment and services and to encourage international autism research.”

Read more: http://www.autismsupportnetwork.com/news/new-study-finds-autism-rates-south-korea-now-1-38-children-38994322#ixzz422yh6O82

According to Dr. Kim, experts disagree about the causes and significance of reported increases in ASD, partly because of variations in diagnostic criteria and incomplete epidemiologic studies that have limited the establishment of actual population-based rates. “We were able to find more children with ASD and describe the full spectrum of ASD clinical characteristics,” said Dr. Kim. “Recent research reveals that part of the increase in reported ASD prevalence appears attributable to factors such as increased public awareness and broadening of diagnostic criteria. This study suggests that better case finding may actually account for an even larger increase. While the current project did not investigate potential risk factors in this particular population, the study does set the stage for ongoing work to examine genetic and environmental factors contributing to the risk of ASD.”

This study is further evidence that autism transcends cultural, geographic, and ethnic boundaries and that autism is a major global public health concern, not limited to the Western world. To date, there is no evidence of differences in the way ASD is expressed in children around the world; however it is possible that cultural factors may impact diagnostic practices and prevalence estimates. As a result, the South Korean study took a comprehensive approach to mitigate potential cultural bias. According to Dr. Grinker, a cultural anthropologist at George Washington University, “Parent and teacher focus groups were conducted to identify local beliefs that might influence symptom reporting and to address stigma and misunderstandings related to ASD. Further, clinical diagnoses were established by Korean diagnosticians with extensive clinical and research experience in both the U.S. and Korea and were validated by North American experts.”

The study does not suggest that Koreans have more autism than any other population in the world. What it does suggest is that autism is more common than previously thought and that, if researchers look carefully, especially in previously understudied, non-clinical populations, they may find more children with ASD. In addition to the South Korean study, Autism Speaks is supporting similar epidemiological research efforts in India, South Africa, Mexico, and Taiwan, including the translation and adaptation of the gold-standard diagnostic instruments into languages spoken by more than 1.7 billion people worldwide.

“This is the first comprehensive population sample-based prevalence calculation in Korea, and replication in other populations is essential,” explained Dr. Dawson. “Notwithstanding the need for replication, this study provides important evidence that the application of validated, reliable and commonly accepted screening procedures and diagnostic criteria applied to a total population has the potential to yield an ASD prevalence exceeding previous estimates.”

“We know that the best outcomes for children with ASD come from the earliest possible diagnosis and intervention,” concluded Dr. Kim and her colleague Dr. Koh from the Korea Institute for Children’s Social Development, “Goyang City, host of the Korea study, has courageously responded to these study findings by providing comprehensive assessment and intervention services for all first graders entering their school system. We hope that others will follow Goyang City’s example so that any population based identification of children with ASD is accompanied by intervention services for those children and their families.”

This research was funded by a Pilot Research Grant from Autism Speaks as well as grants from the Children’s Brain Research Foundation, NIMH and the George Washington University Institute for Ethnographic Research.