The Impact of Metabolic Syndrome and Vitamin D on Hearing Loss in Qatar
Received: 21-Apr-2017 / Accepted Date: 09-May-2017 / Published Date: 16-May-2017 DOI: 10.4172/2161-119X.1000306
Abstract
Aim: The aim of present study to investigate association between metabolic syndrome [MetSyn] and vitamin D deficiency on hearing loss among type 2 diabetes mellitus (T2DM) patients. Subjects and methods: This is an observational cohort study based on 528 subjects aged between 20 and 59 years who visited the Hamad Medical Corporation with hearing difficulty during from January 2013 to July 2014. MetSyn was assessed using the revised NCEP-ATP III criteria. Vitamin D level was evaluated from reported serum 25 (OH) D. A multivariable logistic regression model was performed to evaluate the relation between selected lifestyle factors, MetSyn, vitamin D and presence of hearing loss. Results: The mean age (± SD, in years) for metabolic hearing loss versus normal subjects was 47.7 ± 10.2 vs. 48.5 ± 9.1. Over 90% of the s patients were using phones devices and 13.4% had hearing impairment watching TV. The consanguineous marriages were observed higher in Hearing loss (32.9%) than in normal hearing (23.0%) (p=0.028). The waist circumference, hip circumference, waist hip ratio and body mass index were significantly higher among the participants with MetSyn versus without MetSyn (p<0.001). The mean of diabetes onset duration (9.03 ± 4.35 years), sleeping disorder (5.76 ± 1.32 h), cigarette smoking (16.4%) and sheesha smoking (20.7%) were higher among hearing impairment. The associated risk factors were significantly higher in T2DM with hearing loss, hypoglycemia, retinopathy, Nephropathy and Neuropathy diabetic foot ulcer, Tinnitus, Vertigo and headache than in normal hearing diabetes. There were statistically significant differences between hearing impairment versus normal hearing for vitamin D [18.91 ± 7.65 ng/ml vs 22.85 ± 9.00 ng/ml; p=0.018], magnesium, phosphorous, HDL, ceatinine, albumin, systolic blood pressure and diastolic blood pressure. Further, there were highly statistically significant differences between hearing impairment versus normal for both side right and left ear frequency in Db unit (p<0.001). Multivariable logistic regression analysis revealed vitamin D Deficiency (OR 2.59 95% CI 1.65-4.72; p<0.001), Head ache (OR 1.97 95% CI 1.30-2.85; p<0.001), sleeping disturbance (OR 1.83; 95% CI 1.23-2.71, p=0.002), systolic blood pressure (OR 1.66 95% CI 1.20-2.48; p=0.009), cigarette smoking (OR 1.90 95% CI 1.23-2.95; p=0.004), age in years (OR 1.45; 95% CI 1.30-2.54; p=0.026), nationality (Qatari) (OR 1.55 95% CI 1.10-2.17; p=0.014), diastolic blood pressure (OR 1.69 95% CI 1.14-2.52; p=0.012), age in years (OR 1.45 95% CI 1.30-2.54; p=0.026) and sheesha smokers (OR 1.79; 95% CI 1.32-3.11, p=0.038) were considered at higher risk as a predictors of hearing loss among diabetic patients. Conclusion: The current study results suggests that the impact of metabolic syndrome and vitamin D among diabetic patients were significantly associated with the hearing loss in the Qatari's population
Keywords: Epidemiology; Metabolic syndrome; Hearing loss; Diabetes; Vitamin D; Risk factors
255047Introduction
Type 2 diabetes mellitus (T2DM), one of the main threats to ageing population health in the 21st century, is described as a worldwide epidemic as it affects the health and economy of almost all countries regardless of socioeconomic status or geographic location [1-3]. Diabetes mellitus is a chronic metabolicdisease with abnormal blood glucose levels affects the health and quality of patient’s life [4-8]. There have also been studies that patients with Metabolic Syndrome [MetSyn] diabetes have hearing loss greater than those without [4,5]. Severeal reports stated MetSyn and vitamin D deficiency which may act as important risk factors for the hearing impairment [1,9-12]. More recently some authors have reported that hearing loss has been influenced by diabetes MetSyn [13-17], which hearing loss can affect even the simplest tasks of daily life [16]. Most of authors agree that diabetes mellitus and metabolic syndrome can lead to hearing impairment [1,10,13].
The relation between hearing loss and different health conditions among middle aged population is documented and reported in detailed [9-15]. The aim of present study to investigate association between metabolic syndrome [MetSyn] and vitamin D deficiency on hearing loss among type 2 diabetes mellitus (T2DM) patients.
Subjects and Methods
This is an observational cohort study which was conducted during the period from January 2013 to July 2014 among diabetic patients aged between 20 and 59 years and registered in diabetic and ENT clinics of Hamad General Hospital in Qatar. IRB ethical approval was obtained from Hamad Medical Corporation.
Sampling procedure
The current sample size was determined by considering prevalence rate of 10%-12% impaired hearing loss among diabetes patients in Qatar [1,7], assuming 99% confidence interval and 2% bound on the error of estimation. The minimum sample size detected as 730 subjects. Finally, of the 700 registered with diagnosed diabetes and showed indications, only 528 (72.3%). agreed to participate this study in Hamad General Hospital.
National Cholesterol Education Program–Third Adult Treatment Panel (ATP III) [18,19].
According to ATP III criteria, a participant has the metabolic syndrome [MetSyn] if she/he has three or more of the following criteria : (1) Fasting Plasma Glucose test FPG ≥ 100 mg/dl (5.6 mmol/L) (2) Blood Pressure ≥ 130/85 mm Hg (3) Triglyceride ≥ 150 mg/dl (1.7 mmol/L) (4) high-density lipoprotein (HDL) Cholesterol: Men<40 mg/dl (1.03 mmol/L); Women<50 mg/dl (1.29 mmol/L (5) Men with waist circumference>102 cm and women with waist circumference>88 cm.
Questionnaire
The questionnaire, included socio-demographic, age, gender, nationality, education level, lifestyle habits, Body Mass Index (BMI), co-morbid symptoms, diabetic complications, systolic and diastolic blood pressures, Clinical biochemistry serum triglyceride, total cholesterol, HDL cholesterol, low density lipoprotein (LDL) cholesterol, Hemoglobin A1c (HbA1c) and FPG, were collected.
Physical examination and measurements
BMI was calculated as; weight in kilogram divided by the square of height in meters. According to World Health Organization [WHO] criteria [20], if it is greater than 25 kg/m2, the subjects were assumed as overweight and greater than to 30 kg/m2, the subjects were considered as obese [20]. WHO [20] International Society of Hypertension Writing Group defined standardized criteria of hypertension when Systolic Blood Pressure (SBP) ≥ 140 mm Hg or Diastolic Blood Pressure (DBP) ≥ 90 mm Hg or using anti-hypertensive medication.. Patients who walking or cycling for more than 30 min/day were classified as physically active.
Hearing evaluation procedures
Pure-tone audiometry is a behavioral test used to measure hearing sensitivity. This measure involves the peripheral hearing assessment [20,21]. The clinical digital audiometers (Grason Stadler gsi 61 clinical audiometer was used by pre-trained technicians to test patients' hearing level and calibrated according to ANSI 1996. Hearing loss evaluation described [21-23] as follows: Normal hearing: less than 25 dB in adults and 15 dB in children; Mild hearing loss: 25-39 dB; Moderate hearing loss: 40-69 dB; Severe hearing loss: 70-94 dB; and Profound hearing loss: 95+ dB.
The Statistical Package for Social Sciences (SPSS, version #22) performed for analysis. Student-t test was used to ascertain the significance of differences between two means of a continuous variable. Chi-square test Fisher’s exact test (two-tailed) were performed to test for differences in proportions of categorical variables between two or more groups. Pearson's matrix correlation determines the degree to which a relationship is linear or, it determines whether there is a linear component of association between variables. A multivariable logistic regression analysis was performed to determine the impact and predictors of selected factors on the presence of hearing loss. A p-value of less than 0.05 was considered statistically significant.
Table 1 shows the socio-demographic studied subjects with MetSyn hearing loss and normal hearing among T2DM. The mean age (± SD, in years) for metabolic hearing loss versus normal hearing subjects was 47.7 ± 10.2 vs. 48.5 ± 9.1. The prevalence of was higher in Qataris than in non-Qataris (52.1% vs. 47.9%, p<0.001). Over 90% of the studied patients were using phone devices very frequently and 13.4% had hearing impairment watching TV. The consanguineous marriages were observed higher in Hearing loss (32.9%) than in normal hearing (23.0%) (p=0.028).
| Variables | Metabolic Syndrome Hearing Loss ≥ 26 dB n=140 | Without metabolic Normal Hearing<26 dB n=388 | p-value significance | |
|---|---|---|---|---|
| Age Group in years | 47.7 ± 10.2 | 48.5 ± 9.1 | 0.403 | |
| <35 years | 13 (9.7) | 31 (9.5) | ||
| 35-44.9 years | 25 (18.7) | 74 (22.8) | 0.05 | |
| 45-55 years | 60 (44.8) | 118 (51.7) | ||
| >55 years | 36 (26.9) | 52 (16) | ||
| Gender | ||||
| Male | 55 (41) | 146 (44.9) | 0.446 | |
| Female | 79 (59) | 179 (55.1) | ||
| Nationality | ||||
| Qatari | 80 (59.7) | 151 (46.5) | <0.001 | |
| Non Qatari | 54 (40.3) | 174 (53.5) | ||
| Educational level | ||||
| Illiterate | 22 (16.4) | 59 (18.2) | ||
| Primary | 30 (22.4) | 70 (21.5) | ||
| Intermediate | 20 (14.9) | 68 (20.9) | 0.298 | |
| Secondary | 43 (32.1) | 100 (30.8) | ||
| University | 19 (14.2) | 28 (8.6) | ||
| Occupation | ||||
| Housewife | 87 (64.9) | 191 (58.8) | ||
| Sedentary | 32 (23.9) | 77 (23.7) | ||
| Manual | 10 (7.55) | 47 (14.5) | 0.216 | |
| Businessman | 5 (3.7) | 10 (3.1) | ||
| Do you use a mobile phone frequently | ||||
| Yes | 121 (90.2) | 268 (82.5) | 0.044 | |
| No | 13 (9.8) | 57 (17.5) | ||
| Do you hear TV sounds normally | ||||
| Yes | 112 (86.6) | 292 (89.8) | 0.045 | |
| No | 22 (13.4) | 33 (10.2) | ||
| Income | ||||
| <$2,000 | 49 (36.6) | 112 (34.5) | ||
| $2,000-$4,999 | 48 (35.8) | 127 (39.1) | 0.806 | |
| >$5,000 | 37 (27.6) | 86 (26.5) | ||
| Consanguineous marriage | ||||
| Yes | 43 (32.1) | 71 (21.8) | 0.028 | |
| No | 91 (67.9) | 254 (78.2) | ||
Table 1: Socio demographic characteristics of the subjects with MetSyn hearing impairment comparison with normal hearing among diabetics patients (N= 528).
Table 2 presents the evaluation of the MetSyn hearing loss and normal hearing among T2DM. Average (standard deviation) waist circumference, hip circumference, waist hip ratio and body mass index were significantly higher among the participants with MetS as compared to those without MS (p<0.001). The mean of diabetes onset duration (9.03 ± 4.35 years), sleeping disorder (5.76 ± 1.32 h), cigarette smoking (16.4%) and sheesha smoking (20.7%) were higher among hearing impairment. The associated risk factors were significantly higher in MetSyn with hearing loss such as including hypoglycemia, retinopathy, nephropathy, neuropathy, diabetic foot ulcer, tinnitus, vertigo and headache than in normal hearing T2DM. Similarly, the history of MetS among first degree and second degree relatives were significantly higher among the patients with MetS hering loss compared to those normal hearing.
| Variables | Metabolic Syndrome Hearing Loss ≥ 26 dB n=140 | Without metabolic Normal Hearing <26 dB n=388 | P value |
|---|---|---|---|
| n (%) | n (%) | ||
| Waist circumference (cm) [total sample] | 103.40 ± 10.06 | 99.85 ± 9.50 | <0.001 |
| Hip circumference (cm) | 114.15 ± 10.10 | 112.0075 ± 91 | <0.001 |
| Waist Hip Ratio (WHR) [total sample] | 0.90 ± 0.05 | 0.88 ± 0.06 | <0.001 |
| Body Mass index [BMI] (Kg/m2) | 28.54 ± 5.35 | 27.55 ± 4.08 | 0.024 |
| BMI categories: n (%) | |||
| <25 | 35 (25) | 98 (25.3) | |
| 25-30 | 56 (40) | 177 (45.6) | 0.387 |
| ≥ 30 | 49 (35) | 113 (29.1) | |
| Exposure to sun | 44 (32.0) | 159 (41.0) | <0.001 |
| Walking time per/day | |||
| <30 min | 32 (23.0) | 93 (24.2) | 0.817 |
| <60 min | 40 (28.8) | 97 (25.3) | 0.432 |
| Hours of sleep (Mean ± SD) | 5.76 ± 1.32 | 6.07 ± 1.31 | 0.02 |
| Duration of diabetes | 9.03 ± 4.35 | 8.06 ± 4.29 | 0.025 |
| Cigarette smoking | 20 (15.0) | 37 (11.4) | 0.478 |
| Sheesha Smoking | 27 (20.1) | 41 (12.6) | 0.039 |
| Diabetes complications and symptoms | |||
| Hypoglycemia | 35 (25.3) | 63 (16.2) | 0.022 |
| Retinopathy | 25 (17.9) | 41 (10.6) | 0.025 |
| Nephropathy | 20 (14.3) | 48 (12.4) | 0.281 |
| Neuropathy | 18 (12.9) | 25 (6.4) | 0.017 |
| Macro vascular disease | 16 (11.4) | 32 (8..2) | 0.13 |
| Diabetic foot ulcer | 21 (15.0) | 58 (14.9) | 0.988 |
| Tinnitus | 71 (50.8) | 155 (39.9) | 0.027 |
| Vertigo | 46 (32.9) | 91 (23.5) | 0.03 |
| Headache | 68 (48.6) | 132 (34) | 0.006 |
| Family history of morbidities | |||
| MS in first degree relatives | 33 (23.6) | 64 (16.5) | <0.001 |
| MS in second degree relatives | 29 (20.5) | 47 (12.1) | <0.001 |
| Hypertension | 40 (28.57) | 71 (18.3) | 0.011 |
| CHD | 30 (21.4) | 59 (15.2) | 0.034 |
Table 2: Co-morbidities and family history of morbidities according to metabolic syndrome (N=528), MS=Metabolic syndrome (ATPIII criteria).
Table 3 shows baseline chemistry biomarker values among the two groups. There were statistically significant differences between hearing impairment versus normal hearing for vitamin D [18.91 ± 7.65 ng/ml vs. 22.85 ± 9.00 ng/ml; p=0.018], magnesium [0.81 ± 0.10 mmol/L vs. 0.89 ± 0.08 mmol/L; p<0.001], phosphorous [1.23 ± 0.25 mmol /L vs. 1.36 ± 0.56 mmol/L; p=0.048], HDL [1.33 ± 0.35 mmol /L vs. 1.23 ± 0.32 mmol/L; p=0.002], ceatinine [72.72 ± 17.6 mmol/L vs. 69.1 ± 17.84 mmol/L; p=0.047], albumin [45.37 ± 8.7 mmol/L vs. 40.97 ± 8.52 mmol/L; p=0.044], systolic [131.1 ± 12.60 Hg vs. 128.2 ± 11.16 Hg; p=0.025] and diastolic blood pressure [82.69 ± 6.73 mm Hg vs. 81.23 ± 7.38 mm Hg; p=0.041].
| Variables | Metabolic Syndrome Hearing Loss ≥ 26 dB n= 140 Mean ± SD | Without metabolic Normal Hearing <26 dB Mean ± SD | P value |
|---|---|---|---|
| Vitamin D (ng/ml) | 19.32 ± 7.84 | 21.15 ± 7.74 | 0.018 |
| Hemoglobin (g/dL) | 12.89 ± 2.28 | 12.60 ± 2.03 | 0.296 |
| Magnesium (mmol/L) | 0.81 ± 0.10 | 0.87 ± 0.08 | <0.001 |
| Potassium (mmol/L) | 4.57 ± 0.59 | 4.50 ± 0.63 | 0.503 |
| Calcium (mmol/L) | 1.92 ± 0.44 | 1.90 ± 0.40 | 0.62 |
| Phosphorous (mmol/L) | 1.23 ± 0.25 | 1.30 ± 0.56 | 0.048 |
| Creatinine(mmol/L) | 72.70 ± 17.67 | 69.18 ± 17.84 | 0.047 |
| Fasting Blood Glucose(mmol/L) | 9.26 ± 3.01 | 9.53 ± 2.93 | 0.355 |
| HbA1c | 8.88 ± 1.42 | 8.44 ± 1.57 | 0.003 |
| Cholesterol (mmol/L) | 4.81 ± 1.30 | 4.79 ± 1.02 | 0.821 |
| HDL (mmol/L) | 1.33 ± 0.35 | 1.237 ± 0.32 | 0.002 |
| LDL (mmol/L) | 2.80 ± 0.88 | 3.00 ± 0.79 | 0.465 |
| Albumin (mmol/L) | 45.36 ± 8.70 | 40.97 ± 6.52 | 0.044 |
| Billirubin (mmol/L) | 7.10 ± 3.71 | 8,47 ± 4.70 | 0.009 |
| Triglyceride (mmol/L) | 1.79 ± 0.62 | 1.59 ± 0.47 | 0.001 |
| Uric Acid (mmol/L) | 335.0 ± 101.7 | 332.0 ± 114.0 | 0.845 |
| Systolic Blood Pressure mm Hg | 131.1 ± 12.6 | 128.1 ± 11.16 | 0.025 |
| Diastolic Blood Pressure mm Hg | 82.6 ± 6.7 | 81.2 ± 7.3 | 0.041 |
| Vitamin D Level | n (%) | n (%) | |
| Deficiency | |||
| 25 (OH) D <20 ng/ml | 76 (54.3) | 164 (42.3) | |
| Insufficiency | |||
| 25 (OH) D 20-29 ng/ml | 42 (30.0) | 150 (38.7) | 0.049 |
| Optimal | |||
| 25 (OH) D 30-80 ng/ml | 22 (15.7) | 74 (19.0) |
Table 3: Clinical biochemistry baseline value among hearing loss and normal hearing subject (N=528).
Table 4 shows correlation matrix between hearing loss, metabolic syndrome, tinnitus, vertigo, systolic and diastolic BP and headache. As can be seen from this table the hearing loss was highly significantly correlated with variables such as , tinnitus, vertigo, systolic and diastolic BP and headache.
| Hearing Loss | Metabolic Syndrome | Tinnitus | Vertigo | Vitamin D | Systolic BP | Diastolic BP | Headache | |
|---|---|---|---|---|---|---|---|---|
| Hearing Loss | 1.00 | 0.462** | 0.359** | 0.477** | 0.333** | 0.229** | 210** | 0.265** |
| Metabolic Syndrome | 1.00 | 0.561** | 0.336** | 0.340** | 0.186* | 0.335** | 0.270**. | |
| Tinnitus | 1.00 | 0.539** | 0.246** | 0.458** | 0.322** | 0.328** | ||
| Vertigo | 1.00 | 0.345** | 0.354** | 0.478** | 0.465**. | |||
| Vitamin D | 1.00 | 0.195* | 0.243** | 0.281** | ||||
| Systolic BP | 1.00 | 0.554** | 0.213** | |||||
| Diastolic BP | 1.00 | .294** | ||||||
| Headache | 1.00 |
Table 4: Correlation matrix between hearing loss, Metabolic Syndrome, tinnitus, vertigo, ystolic and diastolic BP and headache, **Correlation is significant at the 0.01 level (2-tailed), *Correlation is significant at the 0.05 level (2-tailed).
Table 5 presents multivariate logistic regression analysis of variables for predictors of hearing loss among diabetic patients. Vitamin D Deficiency (OR 2.59 95% CI 1.65-4.72; p<0.001), Head ache (OR 1.97 95% CI 1.30-2.85; p<0.001), sleeping disturbance (OR 1.83; 95% CI 1.23-2.71, p=0.002), systolic blood pressure (OR 1.66 95% CI 1.20-2.48; p=0.009), cigarette smoking (OR 1.90 95% CI 1.23-2.95; p=0.004), age in years (OR 1.45; 95% CI 1.30-2.54; p=0.026), nationality (Qatari) (OR 1.55 95% CI 1.10-2.17; p=0.014), diastolic blood pressure (OR 1.69 95% CI 1.14-2.52; p=0.012), age in years (OR 1.45 95% CI 1.30-2.54; p=0.026) and sheesha smokers (OR 1.79; 95% CI 1.32-3.11, p=0.038) were considered at higher risk as a predictors of hearing loss among diabetic patients.
| Variables | Odds Ratio (95% CI) | P value |
|---|---|---|
| Vitamin D deficiency | 2.59 (1.65-4.72) | <0.001 |
| Head ache | 1.97 (1.30-2.85) | 0.001 |
| Sleep disturbance | 1.83 (1.23-2.71) | 0.002 |
| Systolic blood pressure | 1.66 (1.20-2.48) | 0.009 |
| Cigarette smoking | 1.90 (1.23-2.95) | 0.004 |
| Diastolic blood pressure | 1.69 (1.14-2.52) | 0.012 |
| Age in years | 1.45 (1.30-2.54) | 0.026 |
| Sheesha Smoking | 1.79 (1.32-3.11) | 0.038 |
Table 5: Multivariate stepwise logistic regression analysis of the association between selected lifestyle factors and presence of hearing loss (n = 528).
Discussion
The current study has revealed hearing loss as an important consequence of diabetes indicating metabolic assessment. Nearly one fourth of the studied diabetics patients suffered from hearing loss which is similar to the findings in some other studies [1,9,10]. MetSyn is a major public health concern because it is associated with hearing loss [1]. Present study revealed evidence that vitamin D deficiency and higher prevalence of MetSyn effect hearing loss [1,16,22,23].The findings of this study concerning symptoms and risk factors are consistent with rates reported elsewhere [1,9-14].
Most recently the results presented by Sun et al. [13] from modelling the association between the presence of metabolic syndrome components and the hearing thresholds are confirmed that there was a strong linear increase in the hearing threshold with the presence of metabolic syndrome components and an increasing number of components of metabolic syndrome. This is consistent with present obtained results.
The impact of vitamin D and MetSyn which influences the hearing loss are not fully understood [1]. Several population-based studies has evaluated the association between diabetes and hearing loss [7-15] and a number of clinical studies have confirmed an association of MetSyn mellitus and hearing loss [11-15,17,22,23]. This is consistent with the current study. Audiometric data obtained in this study revealed that hearing became worse as blood sugar increased in subjects. The present study revealed a big percent of the subjects of hearing loss were diabetic (26.50%) and hypertensive (28.57%).
Other associated risk factors in our middle aged subjects with hearing loss were tinnitus (50.8%), retinopathy (17.9%), nephropathy (14.3%), neuropathy (12.9%), macro vascular disease (11.4%) , vertigo (32.9%) and head ache (48.6%). Those results are consistent with the previous reported studies [9-16]. Overall, diabetes is very complex and co-morbid disease that can affect multiple organs and physiological functions, on the biochemical and molecular levels [1,17,23]. The current investigation showed that MetSyn patients with vitamin D deficiency had poorer hearing levels when compared with normal subjects.
Conclusion
The current study results suggests that the impact of metabolic syndrome and vitamin D among diabetic patients were significantly associated with the hearing loss in the Qatari's population.
Contributors
AB designed and supervised the study and was involved in data collection, statistical analysis the writing of the paper. AOAA , KA and LG were involved in data collection, interpretation of data and writing manuscript. All authors approved the final version.
Acknowledgment: This work was generously supported and funded by the Qatar Diabetes Association, Qatar Foundation. The authors would like to thank the Hamad Medical Corporation for their support and ethical approval (HMC RP # 10213/10 HMC RP # 11147/13 and13234/13, IRB# 13-00063).
Competing Interests
None to declare
References
- Bainbridge KE, Hoffman HJ, Cowie CC (2008) Diabetes and hearing impairment in the United States: Audiometric evidence from the National Health and Nutrition Examination Survey, 1999 to 2004. Ann Intern Med 149: 1-10.
- Campbell KC (1998) The basic audiologic assessment. Essential audiology for physicians. Singular Publishing Group Inc.
Citation: Bener A, Al-Hamaq AOAA, Abdulhadi K, Salahaldin AH, Gansan L (2017) The Impact of Metabolic Syndrome and Vitamin D on Hearing Loss in Qatar. Otolaryngol (Sunnyvale) 7:306. DOI: 10.4172/2161-119X.1000306
Copyright: © 2017 Bener A, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distributionand reproduction in any medium, provided the original author and source are credited.
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