Original article


Factors associated with regular sunscreen use by medical students of a Peruvian university

P. RodRíguez-gambetta1, m.g. moscoso-PoRRas2, a. tayPe-Rondan2

1 Faculty of medicine, universidad de san martín de Porres, Lima, Peru; 2 cRonIcas center of excellence for chronic diseases, universidad Peruana cayetano Heredia, Lima, Peru


Keywords

image

Sun protection • Sunscreen • Ordinal logistic regression


Summary

image


Introduction. Use of sunscreen is encouraged to reduce the risk of skin pathologies caused by radiation. It is important to acknowl- edge the associated factors that promote or hinder sunscreen use in young populations as to design better prevention policies.

Objective. To determine the factors associated with regular sun- screen use among first year medical students from a Peruvian university.

Materials and methods. A cross-sectional study was performed. Our population was first-year medical students from a Peruvian university. We administrated an electronic survey to evaluate socio-demographic data, as well as student knowledge, attitudes, and practices regarding photo-protection. We used ordinal logistic regression to analyze the factors associated with sunscreen use. Results. Of 420 first-year students, 299 completed our survey. We found that 53.5% of the participants were less than 18 years old,

63.2% were female, 9.3% (females more than males) responded that a sunburn was worth it to look tan, and 38.1% always or almost always used sunscreen during the summer. Factors associ- ated with sunscreen use in the ordered logistic adjusted regression were male sex (OR = 0.50, IC95% = 0.34-0.86), participation in photo-protection workshops within the last year (OR = 2.40, IC95% = 1.28-4.37), and having somebody to remind them the use of sunscreen during the last three months (OR = 3.80, IC95% = 1.28-11.20).

Conclusions. In our sample, a higher sunscreen use was more often observed among female participants, those who attended skin protection workshops, and those reminded to use sun- screen. This highlights the importance of educational and reminder activities in the adoption of protective habits, such as sunscreen use.


Introduction


Regulated sun exposure is beneficial to human beings because it prevents autoimmune diseases, helps produce vitamin D3, is beneficial for certain skin diseases such as psoriasis, and increases the serum levels of endorphins [1]. However, excessive sun exposure is related to the develop- ment of skin cancer, skin damage, photoaging, eye prob- lems, DNA mutations, and immune system damage [2].

Skin cancer is the major consequence of excessive sun exposure [3, 4]. According to the World Health Organi- zation (WHO), one of every three cancers detected in the world is a skin cancer [5]. As such, WHO recommends many photo-protective methods such as: seeking shade, use of sunscreen, skin-covering clothes, hats, and sun- glasses with UV filters [6].

Up to 80% of the radiation absorbed during one’s entire life is absorbed during childhood and adolescence [7, 8]. So, the best way to prevent the consequences of exces- sive sun exposure, including skin cancer, is to promote regular use of photoprotective methods from early ag- es [3, 4].

Use of sunscreen is one of the most recommended pho- toprotective methods. Unfortunately, it is frequently sub-optimally utilized, especially among adolescents and young adults [9]. Use of sunscreen in teenagers and


young adults has been evaluated in several studies where the prevalence fluctuates between 26% and 78% [10-12] It has been found that sunscreen use is related to some characteristics such as female sex, adult supervision, habits ingrained during childhood, prior awareness, pre- vious sunburns, expertise in the topic, previous use of tanning beds, warmer climates, and skin color [12-16]. However, these factors are context-dependent, so they can vary between regions.

Little has been described about these factors in Latin America [14, 17]. This lack of information hinders the design and enhancement of public policies aimed to pro- mote the use of photoprotective methods in young peo- ple, in order to prevent a variety of skin diseases, includ- ing skin cancer. Thus, the aim of this study is to assess the factors associated with the regular use of sunscreen in university medical students.


Materials and methods


Study design and setting

During April 2014, we conducted a descriptive study among first year medical students from the Universidad de San Martín de Porres (USMP). The USMP is a pri- vate university located in Lima, the capital city of Peru.

Students are usually middle class and come from all over the country.


Participants

Participants were all first year medical students who were enrolled according to a USMP database. By 2014, a total of 420 students were registered at the university. We perform the survey in those who agreed to partici- pate in the study after reading an informed consent. Par- ticipants whose surveys were less than 80% complete were excluded from the analyses.


Procedure

Prior to the completion of this study, we obtained proper approval from the USMP ethics committee (IRB). We developed a consent form and survey based on the cur- rent literature. Both formats were posted on the USMP “virtual classroom”, so all first-year students could ac- cess both documents with a personalized password.

We approached first-year students during class periods in the computer lab to request their participation. The re- searchers were present during the survey completion to answer participants’ questions. Students unable to take the survey during their class period were granted the opportu- nity to complete it outside class hours.


Variables


Use of sunscreen

The use of sunscreen was measured by the statement: “during the last summer, when you were out in the sun, you used sunscreen…”, and the options: “never, almost never, sometimes, almost always, or always”. Later, this variable was categorized into three categories (Never/ Almost never, Sometimes, and Always/Almost always) to perform the ordinal logistic regression.

For the record, Peruvian summer occurs during January- March, and the survey was completed during April.


Other variables

The survey included five sections: demographic data (sex, age, place of birth, diagnosed skin disease, familiar or known person with skin cancer), self-identified skin phototype according to the Fitzpatrick classification (18), attendance to a photoprotective workshop, having someone remind you to use sunscreen in the last three months, knowledge of sun protection, attitudes regard- ing sun exposure, and assessment of usual photo-protec- tive methods (use of sunglasses with UV filters, hats or caps, umbrellas and long sleeves).


Statistical analysis

Data from the surveys were extracted from the virtual classroom, and exported into a Microsoft Excel data- base. Subsequently, surveys with less than 80% comple- tion were eliminated from the database.

Data was analyzed using STATA v13 (StataCorp, Col- lege Station, TX, US). For descriptive analysis, we used frequencies and percentages. For bivariate analysis, we

used Chi-squared tests with level of significance of 5% or Fisher’s exact test when expected frequencies in con- tingency tables were less than five.

Finally, as the outcome variable (sunscreen use) had an ordinal level of measurement, we used crude and ad- justed ordinal logistic regression after testing the pro- portional odds assumption to determine the associated factors. Adjusted regression included all variables tested in the crude analysis.


Ethical issues

Participation in this study was voluntary, as stated in the consent form. To ensure the anonymity of the partici- pants, personal data (such as names, numbers of identity documents, and so on) were not requested. Moreover, the database was handled only by the researchers.


Results


Participants characteristics

We requested the participation of all 420 first-year medi- cal students enrolled in the USMP in 2014, from which 321 (76.4%) took the survey. After quality control, 22 surveys were eliminated for being incomplete; leaving 299 (71.2%) surveys for analysis.

Univariate analysis reveals that 53.5% of the partici- pants were less than 18 years old, 63.2% were female, and 67.2% were born in Lima (capital city of Peru). With respect to the skin phototype, 46.1% had phototypes I, II or III, and 40.5% had phototype IV. With respect to the personal and familiar history, 15.7% had a skin disease, and 8.0% had a family member with known skin cancer (Tab. I).


Knowledge, attitudes and practices

Around 97.0% of the participants correctly answered that solar radiation is a major cause of skin cancer, but only 72.9% correctly answered that a sunscreen of SPF 15 is not better than one of SPF 30, moreover, only 23.1% correctly answered that on a cloudy day it is also necessary to use the sunscreen (Tab. II).

Regarding perceptions, 87.0% of the participants affirm that it is worth to use sunscreen to avoid future health problems, 18.2% believe that tan people look more at- tractive, and 9.3% responded that it is worth to get a sun- burn to look tan. This last perception was higher among females than males (p = 0.021).

With respect to the use of photoprotective methods, we found that the respondents always or almost always walked in the shade (66.9%), used sunscreen (38.1%), and wore long pants (30.1%). The use of sunscreen and long pants were higher among females than males (p = 0.010 and p = 0.011, respectively) (Tab. III).


Factors associated with the use of sun protection

Factors directly associated with a higher use of sun- screen in the ordered logistic adjusted regression


Tab. I. demographic data in first-year medical students at a private university in Lima, peru 2014 (N = 299).


Tab. II. Knowledge about solar exposure and the use of sunscreen in first-year medical students at a private university in Lima, peru 2014.


Knowledge

Yes N (%)

Do not know N (%)

No N (%)

Solar radiation is a major cause of skin cancer?

290

(97.0)

6

(2.0)

3

(1.0)

A person with dark skin also needs to use sunscreen?

289

(96.7)

4

(1.3)

6

(2.0)

The use of sunscreen prevents skin cancer?

276

(92.3)


5 (1.7)

18

(6.0)

A sunscreen of SpF 15 is better than one of SpF 30?


22 (7.4)


59 (19.7)

218

(72.9)

On a cloudy day it is also necessary to use the sunscreen?

69

(23.1)


17 (5.7)

213

(71.2)

When using sunscreen, Can you expose to the sun without risk?

70

(23.4)


11 (3.7)

218

(72.9)


Characteristics

N (%)

Age

< 18 years old

160 (53.5)

18-19

112 (37,5)

20 or more

27 (9,0)

Sex

Female

189 (63.2)

male

110 (36.8)

place of birth

peru: Lima City

201 (67.2)

peru: Other

81 (27.1)

Foreign

17 (5.7)

Fitzpatrick Skin phototype

I-III

138 (46.1)

Iv

121 (40.5)

v- vI

40 (13.4)

diagnosed skin disease

No

252 (84.3)

yes

47 (15.7)

Familiar or known with skin cancer

No

275 (92.0)

yes

24 (8.0)

have you ever attended to a workshop about photoprotective methods?

Never

181 (60.5)

yes / Long ago

66 (22.1)

yes / This year

52 (17.4)

did somebody remind you to use sunscreen in the last three months?

Never

4 (1.3)

during childhood

11 (3.7)

during the last months

11 (3.7)

Both

273 (91.3)

Characteristics

N (%)

Age

< 18 years old

160 (53.5)

18-19

112 (37,5)

20 or more

27 (9,0)

Sex

Female

189 (63.2)

male

110 (36.8)

place of birth

peru: Lima City

201 (67.2)

peru: Other

81 (27.1)

Foreign

17 (5.7)

Fitzpatrick Skin phototype

I-III

138 (46.1)

Iv

121 (40.5)

v- vI

40 (13.4)

diagnosed skin disease

No

252 (84.3)

yes

47 (15.7)

Familiar or known with skin cancer

No

275 (92.0)

yes

24 (8.0)

have you ever attended to a workshop about photoprotective methods?

Never

181 (60.5)

yes / Long ago

66 (22.1)

yes / This year

52 (17.4)

did somebody remind you to use sunscreen in the last three months?

Never

4 (1.3)

during childhood

11 (3.7)

during the last months

11 (3.7)

Both

273 (91.3)

were: participation in at least one workshop about photoprotective methods in the last year (OR = 2.37, IC95% = 1.28-4.37) and having somebody to remind them the use of sunscreen during the last summer (OR = 3.78, IC95% = 1.28-11.21). While male sex

(OR = 0.54, IC95% = 0.34-0.86) was inversely associ- ated (Tab. IV).



Tab. III. perceptions and practices about solar exposure and photoprotective methods in first-year medical students at a private university in Lima, peru 2014.

Total N = 299

Male N = 110

Female N = 189

p*

perceptions (Agree with)

It is worth to use sunscreen to avoid future health problems

260 (87.0)

96 (87.3)

164 (86.8)

0.526

Tan people is more attractive

54 (18.2)

24 (21.8)

30 (15.9)

0.129

It is worth it to get a sunburn to look tan

28 (9.3)

5 (4.6)

23 (12.2)

0.021

Tan people is more healthy

20 (6.7)

4 (3.6)

16 (8.5)

0.082

practices during the last summer (Always/Almost always)

Walk in the shadow

200 (66.9)

73 (66.4)

127 (67.2)

0.491

Sunscreen

114 (38.1)

32 (29.1)

82 (43.4)

0.010

Large pants

90 (30.1)

24 (21.8)

66 (34.9)

0.011

Sunglasses with Uv filters

86 (28.8)

25 (22.7)

61 (32.3)

0.051

Not going out in the hours of higher radiation

86 (28.8)

28 (25.5)

58 (30.7)

0.203

hats or caps

53 (17.7)

25 (22.7)

28 (14.8)

0.059

Umbrella

37 (12.4)

11 (10.0)

26 (13.8)

0.223

Long sleeves

24 (8.0)

11(10.0)

13 (6.9)

0.228

* Fisher’s exact test

Tab. IV. Factors associated with the use of sunscreen in first-year medical students at a private university in Lima, peru 2014.


Characteristics

Use of sun screen N (%)

Crude model

Adjusted model*

Never/ Almost never


Sometimes

Always/ Almost always


Or


IC 95%


p


Or


IC 95%

p

Age

< 18 years

31 (19.4)

70 (43.7)

59 (36.9)

ref.

ref.

≥ 18 years

37 (26.6)

47 (33.8)

55 (39.6)

0.92

(0.60-1.40)

0.700

0.82

(0.53-1.27)

0.383

Sex

Female

33 (17.5)

74 (39.1)

82 (43.4)

ref.

ref.

male

35 (31.8)

43 (39.1)

32 (29.1)

0.50

(0.32-0.78)

0.002

0.54

(0.34-0.86)

0.009

Fitzpatrick Skin phototype

I-III

24 (17.4)

53 (38.4)

61 (44.2)

ref.

ref.

Iv

32 (26.4)

49 (40.5)

40 (33.1)

0.61

(0.39-0.96)

0.035

0.67

(0.41-1.09)

0.103

v-vI

12 (30.0)

15 (37.5)

13 (32.5)

0.56

(0.29-1.07)

0.080

0.58

(0.30-1.14)

0.115

diagnosed skin disease

No

59 (23.4)

95 (37.7)

98 (38.9)

ref.

ref.

Si

9 (19.2)

22 (46.8)

16 (36.0)

0.96

(0.55 - 1.70)

0.899

1.00

(0.55-1.78)

0.971

Familiar or known with skin cancer

No

60 (21.8)

110 (40.0)

105 (38.2)

ref.

ref.

Si

8 (33.3)

7 (29.2)

9 (37.5)

0.75

(0.34 - 1.68)

0.489

0.8

(0.34-1.71)

0.509

have you ever attended to a workshop about photoprotective methods?

Never

47 (25.9)

70 (38.7)

64 (35.4)

ref.

ref.

yes/ Long ago

14 (21.2)

31 (47.0)

21 (31.8)

1.01

(0.60 - 1.70)

0.954

1.00

(0.59 - 1.71)

0.983

yes/ In the last year

7 (13.5)

16 (30.8)

29 (55.7)

2.34

(1.29 - 4.27)

0.005

2.37

(1.28 - 4.37)

0.006

did somebody remind you to use sunscreen during the last summer?

No

9 (60.0)

3 (20.0)

3 (20.0)

ref.

ref.

yes

59 (20.8)

114 (40.1)

111 (39.1)

1.56

(0.49 - 2.62)

0.004

3.78

(1.28 - 11.21)

0.016

*Adjusted model include every variable presented


Discussion


Knowledge

In this study, we found that 97.0% of the participants knew about the relationship between sun exposure and skin can- cer. These results are consistent with other studies com- pleted in Australia where 80% of teenagers were compe- tent regarding the dangers of sun exposure [16], and with research made in United States of America (USA), where 89% of the adolescents knew about the association between unprotected sun exposure and skin cancer [19].

Fewer participants answered correctly about adequate sun- screen use: 71.2% answered that on a cloudy day it is not necessary to use the sunscreen, and 7.4% answered that a sunscreen of SPF 15 is better than one of SPF 30. These percentages are similar to other studies [19], and reflect that information regarding correct sunscreen use is not yet widely dispersed. These results suggest the necessity to im- prove population-level knowledge on this subject, as pre- vious studies have shown the positive association between high knowledge and a lower sunburn incidence [13].


Practices and perceptions

The perception that it is worth to get a sunburn to look tan was higher among females than males. Results

were similar with other studies [13, 16]. This may be due to the arraigned social perceptions of beauty and fashion, which are especially strong in female adoles- cents [20, 21]. Educational campaigns must take this into consideration and make appropriate recommenda- tions [22].

The most commonly used photoprotective methods were walking in the shade, use of sunscreen, and the use of long pants. Nevertheless, sunscreen was used “always” or “almost always” by only 38.1% of the population. These results are consistent with previous data, where only 31.4% of the adolescents used sunscreen frequent- ly [19].

Nearly a third of the participants used sunglasses with UV filters “always” or “almost always”. Similar re- sults found in other studies was the use of sunglasses (32.2%) as one of the most common sun-protection behaviors [19]. Although not statistically significant (p = 0.051), our findings suggest that women are more likely to use sunglasses (32.3%) than with men (22.7%). These results were consistent with previous studies, where men use sunglasses less often [16]. This could re- flect a difference in sun protection awareness, or in fash- ion customs, between males and females.

Factors associated with the use of sunscreen

In the multiple regression analysis, a higher use of sun- screen was associated with female sex. This result is similar to other studies [13, 16], and could be explained by differences in cultural roles between young males and females. Women are more concerned with personal care and skin rotection than men [23].

Attending a sunscreen workshop in the last year was also associated with increased sunscreen use. Other studies found that adequate educational campaigns could eradi- cate myths and improve the quality of sunscreen use among young people [15, 17].

Other protective factor was having a person who has re- minded them to use to use sunscreen in the last three months. In general, it seems that one of the biggest barri- ers hindering sunscreen use is forgetting to apply it [24] and lack of habit [14].


Recommendations

Our findings suggest that it is necessary to organize sunscreen educational activities for middle class urban children and adolescents. These activities should include information concerning the correct sunscreen use, and sex-specific recommendations, such as avoid tanning for women and use of photoprotective methods for men. These activities could be implemented in schools, uni- versities, and recreational settings [25].

Although not all young people have somebody to re- mind them about this topic, there are new methods to inform youth about sun protection (i.e., text messages or Smartphone applications) , which have already been used effectively [24]. These methods should be tested and implemented in young Peruvian population.

Nevertheless, the participants of this study are urban middle-class medical students. Therefore, our findings cannot be extrapolated to populations of lower socioeco- nomic status or rural dwellers who probably have dif- ferent challenges in accessing educational and reminder activities that help to reinforce healthy habits.


Limitations

The present study has some limitations: first, it is pos- sible that participants, well-educated medical students, have a greater interest and knowledge-fund than the general Peruvian population. Moreover, the use of sun- screen as well as other variables were collected through an electronic survey, which are subjected to recall bias, as participants surveyed are in their first years of study, so we believe that their knowledge is not very different from that of other university freshmen.


Conclusions


In conclusion, our findings show that the main factors related to a higher sunscreen use in our population are being female, having attended safe-sun workshops, and having a person who reminds them to use sunscreen. Moreover, perceptions and practices related solar ex- posure and photoprotective methods differ according

to sex. These results should be taken into consideration when developing educational programs aimed at young middle class urban populations.

Acknowledgements

Authors wish to thank Elizabeth Abbs for her assistance in the manuscript redaction. Also, we would like to thank the Universidad de San Martín de Porres staff that kindly allowed us to collect data through their virtual database.


Acknowledgements


Authors declared they have no conflicts of interest re- garding the content of this article.

The present study was self-funded. ORCID

PR-G: orcid.org/0000-0002-6660-059X MGM-P: orcid.org/0000-0001-9518-4241 AT-R: orcid.org/0000-0001-8758-0463


Authors’ contribution


PR-G and AT-R contributed to the conception and design of this study. PR-G planned and performed data collec- tion and prepared the first manuscript draft. AT-R and MGM-P provided feedback for all the manuscript ver- sions. MGM-P and AT-R performed the statistical analy- ses. All authors revised and approved the final version of the manuscript.


References


[1] Mead MN. Benefits of sunlight: a bright spot for human health.

Environ Health Perspect 2008;116:A160.

[2] Lim HW, Cooper K. The health impact of solar radiation and prevention strategies. J Am Acad Dermatol 1999;41:81-99.

[3] Oliveria SA, Saraiya M, Geller AC, Heneghan MK, Jorgens- en C. Sun exposure and risk of melanoma. Arch Dis Child 2006;91:131-8.

[4] Gallagher RP, Hill GB, Bajdik CD, Fincham S, Coldman AJ,McLean DI, Threlfall WJ. Sunlight exposure, pigmentary factors, and risk of nonmelanocytic skin cancer: I. Basal cell carcinoma. Arch Dermatol 1995;131:157-63.

[5] Organization. WH. Skin cancers: World Health Organization; 2016 [cited 2016 march 13]. Available from: http://www.who. int/uv/faq/skincancer/en/index1.html.

[6] World Health Organization. What are simple action steps for sun protection? World Health Organization; 2014 [cited 2016 March 13]. Available from: http://www.who.int/features/qa/40/en/.

[7] Stanton WR, Janda M, Baade PD, Anderson P. Primary preven- tion of skin cancer: a review of sun protection in Australia and internationally. Health Promot Int 2004;19:369-78.

[8] Stankeviciūte V, Zaborskis A, Petrauskiene A, Valiukeviciene S. Skin cancer prevention: children’s health education on protec- tion from sun exposure and assessment of its efficiency. Medici- na (Kaunas, Lithuania) 2003;40:386-93.

[9] Heckman CJ, Manne SL, Kloss JD, Bass SB, Collins B, Lessin SR. Beliefs and intentions for skin protection and exposure. Am J Health Behav 2011;35:699.

[10] Banks BA, Silverman RA, Schwartz RH, Tunnessen WW. At- titudes of teenagers toward sun exposure and sunscreen use. Pediatrics1992;89:40-2.

[11] Grunfeld EA. What influences university students’ intentions to practice safe sun exposure behaviors? J Adolesc Health 2004;35:486-92.

[12] Geller AC, Colditz G, Oliveria S, Emmons K, Jorgensen C, Aweh GN, Frazier AL. Use of sunscreen, sunburning rates, and tanning bed use among more than 10 000 US children and ado- lescents. Pediatrics 2002;109:1009-14.

[13] Saridi M, Bourdaki E, Rekleiti M. Young students’ knowledge about sun protection and its relation with sunburn incidence. A systematic review. Health Science Journal 2014;8:4-20.

[14] Laffargue JA, Merediz J, Buján MM, Pierini AM. Encuesta so- bre protección solar en adolescentes deportistas de la Provincia de Buenos Aires. Arch Argent Pediatr 2011;109:30-5.

[15] Liu KE, Barankin B, Howard J, Guenther LC. One-year fol- lowup on the impact of a sun awareness curriculum on medical students’knowledge, attitudes, and behavior. J Cutan Med Surg 2001;5:193-200.

[16] Livingston P, White V, Ugoni A, Borland R. Knowledge, atti- tudes and self-care practices related to sun protection among secondary students in Australia. Health Educ Res 2001;16:269- 78.

[17] Valverde AGR, Castro DE, Cortés GEP. Encuesta sobre el es- caso uso de métodos de protección solar en Zacatecas, México. Dermatol Rev Mex 2013;57:220-2.

[18] Katz FEWAG. Fitzpatrick’s Dermatology In General Medicine.

2003.

[19] Cokkinides VE, Johnston-Davis K, Weinstock M, O’Connell MC, Kalsbeek W, Thun MJ, Wingo PA. Sun exposure and sun- protection behaviors and attitudes among US youth, 11 to 18 years of age. Prev Med 2001;33:141-51.

[20] Schwebel DC. Adolescent tanning, disordered eating, and risk taking. J Dev Behav Pediatr 2014;35:225-7.

[21] Kyle RG, MacMillan I, Forbat L, Neal RD, O’Carroll RE, Haw S, Hubbard G. Scottish adolescents’ sun-related behaviours, tanning attitudes and associations with skin cancer awareness: a cross-sectional study. BMJ Open. 2014;4:e005137.

[22] Morris KL, Cooper DP, Goldenberg JL, Arndt J, Gibbons FX. Improving the efficacy of appearance-based sun exposure in- terventions with the terror management health model. Psychol Health 2014;29:1245-64.

[23] Schofield PE, Freeman JL, Dixon HG, Borland R, Hill DJ. Trends in sun protection behaviour among Australian young adults. Aust N Z J Public Health 2001;25:62-5.

[24] Armstrong AW, Watson AJ, Makredes M, Frangos JE, Kimball AB, Kvedar JC. Text-message reminders to improve sunscreen use: a randomized, controlled trial using electronic monitoring. Arch Dermatol 2009;145:1230-6.

[25] Saraiya M, Glanz K, Briss PA, Nichols P, White C, Das D, Smith SJ, Tannor B, Hutchinson AB, Wilson KM, Gandhi N, Lee NC, Rimer B, Coates RC, Kerner JF, Hiatt RA, Buffler P, Rochester P. Interventions to prevent skin cancer by reduc- ing exposure to ultraviolet radiation: a systematic review. Am J Prev Med 2004;27:422-66.


n Received on March 6 , 2016. Accepted on June 21, 2016.


n Correspondence: Alvaro Taype-Rondan, CRONICAS Center of Excellence for Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru, Avenida Armendáriz 497, Miraflores, Lima 18, Peru - Tel. +51 970001517 - E-mail: alvaro.taype.r@upch.pe