Smoking and Its Association with Cataract: Results of
the Andhra Pradesh Eye Disease Study from India
- Sannapaneni Krishnaiah,
- Kovai Vilas,
- Bindiganavale R. Shamanna,
- Gullapalli N. Rao,
- Ravi Thomas
and - Dorairajan Balasubramanian
+ Author Affiliations
(http://www.iovs.org/content/46/1/58.full) (28.09.2013)
(www.karmayog.org)
Abstract
purpose. To investigate the
associations between tobacco smoking and various forms of cataracts among the
people of a state in India.
methods. A population-based
cross-sectional epidemiologic study was conducted in the south Indian state of
Andhra Pradesh (AP). A total of 10,293 subjects of all ages from one urban and
three rural areas, representative of the population of AP, were interviewed,
and each underwent a detailed dilated ocular evaluation by trained
professionals. Data were analyzed for 7416 (72%) of the subjects aged >15
years.
results. Increasing age was
significantly associated with all cataract types and history of prior cataract
surgery and/or total cataract. In multivariate analyses, after adjusting for
all demographic factors and for history of smoking, females, illiterate
persons, and those belonging to the extreme lower socioeconomic status group
were found to have a significantly higher prevalence of any cataract, adjusted
odds ratio (OR) = 1.60 (95% confidence interval [CI]: 1.241.96), 1.46 (95% CI:
1.171.70), and 1.92 (95% CI: 1.143.24), respectively. After adjustment,
cigarette and cigar smokers had a significantly higher prevalence of any
cataract, adjusted OR = 1.51 (95% CI: 1.102.06) and 1.44 (95% CI: 1.121.84),
respectively, compared with those who had never smoked (never-smokers). A
significantly higher prevalence of nuclear, cortical cataract, and history of
prior cataract surgery and/ or total cataract was found among cigarette
smokers. A doseresponse relationship was seen with respect to cigarette and
cigar smoking. After adjustment, compared with never-smokers, cigarette smokers
who smoked heavily (>14 pack-years of smoking) had a significantly higher
prevalence of nuclear cataract (OR = 1.65; 95% CI: 1.102.59), cortical
cataract (OR = 2.11; 95% CI: 1.383.24), and history of prior cataract surgery
and/or total cataract (OR = 2.10; 95% CI: 1.054.22). Nuclear cataract was
significantly higher in cigar smokers (adjusted OR = 1.55; 95% CI: 1.162.01)
and in cigar smokers who smoked heavily (>21 person-years of smoking; OR=
1.50; 95% CI: 1.101.95), compared with never-smokers.
conclusions. Consistent with other
studies, tobacco smoking was strongly associated with a higher prevalence of
nuclear and cortical cataracts and history of prior cataract surgery in this
population. These findings suggest yet another need to educate the community on
the importance of cessation of tobacco smoking and perhaps incorporating an
antismoking message into school health programs.
Introduction
Cataract is a major cause of
avoidable blindness and visual impairment throughout the world. The challenges
are to prevent or delay cataract formation, and treat that which does occur.1 Although safe
and effective technologies are available that could restore normal vision to a
large number of those affected, the cataract burden continues to increase
annually, because of the backlog of patients to be operated on, and the growing
number of cataract cases, due to increased life expectancy. Although surgery is
the only effective treatment option available, identifying risk factors may
help to establish preventive measures and appropriate strategies at the level
of primary or primordial prevention. The World Health Report, published in
1998, estimated that there were 19.34 million people who were bilaterally blind
(visual acuity <3/60 in the better eye) due to age-related cataract.2 In the Andhra
Pradesh Eye Disease Study (APEDS) conducted by our institute, it has been
reported that cataract alone contributes to 44% of the total blindness in
India.3 Intervention
against cataract blindness has received priority attention in the global
initiative called VISION 2020: The Right to Sight.4 5 6
Cigarette smoking is an established
risk factor for nuclear cataract, and there is growing epidemiologic evidence
that smoking is also a risk factor for posterior subcapsular cataract.7 It has been
shown to be a risk factor for many common and severe eye diseases, such as
age-related macular degeneration, glaucoma, and cataract, which can lead to
irreversible blindness.8 Several
studies9 10 11 12 13 14 15 16 17 18 19 have
investigated and reported the significant relationship between cigarette
smoking and an increased risk of cataract development. Despite the
multifactorial etiology of these ocular syndromes, smoking is an independent
risk factor that has doseresponse effects. It causes morphologic and
functional changes to the lens and retina due to its atherosclerotic and
thrombotic effects on the ocular capillaries. In addition, evidence exists that
cigarette smokers are more at risk of development of cataract at an earlier age
than are nonsmokers.11 12
We focus attention on habitual
tobacco smoking in men and women in the state of Andhra Pradesh (AP, population
~65 million) in India, and the connection between smoking and
cataract in this population. India is the second largest tobacco producer in
the world, and the state of AP accounts for almost 40% of the countrys tobacco
production. The practice of smoking, particularly home-rolled cigars called
chutta, is highly prevalent among its people, rural and urban, women and men.
As part of the comprehensive APEDS, we have attempted for this article to
investigate the association between tobacco smoking and various forms of
cataract in AP.
Subjects
and Methods
The details of various aspects of
design of the APEDS have been described previously.3 20 21 22 Approval of
the Ethics Committee of the Institute was obtained for the study design, which
was conducted during the 5-year period 1996 to 2000, in compliance with the
tenets of the Helsinki Declaration.
Briefly, a multistage sampling
procedure was used to select the study sample of 10,000 persons, with 5,000
each older and younger than 30 years based on the assumption that a 0.5%
prevalence of an eye disease in either of these groups may be of public health
significance. One urban and three rural areas from different parts of AP were
selected. Approximately 2950 persons were sampled in each of the four areas
with the intent of including ~2500 participants in each area, so
as to reflect the urbanrural and socioeconomic distribution of the population
of this state. These four areas were located in Hyderabad (urban, stratified by
socioeconomic status and religion), the West Godavari district (economically
well off, rural), and the Adilabad and Mahabubnagar districts (poor, rural). To
obtain a sample representative of the entire population of the city of
Hyderabad, we stratified the urban blocks by socioeconomic status and religion,
because these variables might influence ocular morbidity. Because details of
socioeconomic status were not available, we stratified blocks based on our
knowledge of Hyderabad gained from various sources, including a surveyor with
27 years field experience in Hyderabad. The socioeconomic strata were extreme
low (monthly income per person, = 200 rupees (US$ 4.31), low (201500 rupees),
middle (5012000 rupees), and high (>2000 rupees). We assumed that 0.7% of
the Hyderabad population was homeless (no accurate data were available) and included
those people in the lowest socioeconomic stratum. We stratified blocks by two
major religious groups, Hindu and Muslim, based on location, because people of
the same religion tend to live in the same areas. For practical purposes, we
assumed that socioeconomic status and religion were homogeneous within each
block. We chose 23 blocks (clusters) and one cluster of homeless people by
stratified random sampling with an equal probability of selection. The selected
blocks were mapped, and the number of households listed. We randomly selected
every third to fifth household depending on the total number of households in
each block, to obtain a similar number of households in all blocks. We selected
2954 people from Hyderabad with the purpose of achieving a recruitment rate of
at least 85% from these blocks.
From three rural areas in different
parts of the state, 70 rural clusters were selected with the purpose of having
a study sample representative of the socioeconomic distribution of the rural
population of the state. We sampled 8832 subjects from these three rural areas,
of whom 7771 participated in the study. The major difference between the urban
and rural samples was that the former was selected from blocks stratified by
socioeconomic status and religion, whereas the latter were selected from
villages stratified by four different castes (forward caste, backward caste,
scheduled caste, and scheduled tribe) assuming that the different castes
roughly reflect the different socioeconomic strata in these rural areas.
Interview
The volunteers were interviewed in
detail by trained field investigators.20 A structured
questionnaire was used to collect the information on current and prior status
of cigarette, beedi (a leaf-rolled cigarette), hookah (the
hubble-bubble or the flexible, water-filtered smoking pipe), and chutta
(a home-rolled cigar sold and used extensively in the state) smoking. The first
question related to smoking was on the current status of smoking (yes/no). If
the response was yes, the volunteer was asked how long he/she had been smoking
(years) and current level (in terms of number per day for cigarettes/beedies/chuttas;
hours per day for the hookah) of smoking. Similar information was also
obtained from those who were once smokers but had since given up (i.e., prior
smokers). In addition, data on cooking status was ascertained from each
volunteer as part of the structured questionnaire. The first question related
to cooking status asked was, Do you cook regularly? If yes, the participant
was asked about the type of fuel mainly used for cooking.
Ophthalmologic
Examination
Two ophthalmologists and two
optometrists, specially trained in the procedures used in this study, performed
the examinations. Distance and near visual acuity, both presenting and best
corrected after refraction, were measured under standard distance and lighting
conditions using logarithm of minimum angle of resolution (logMAR) charts23 obtained from
Australian Vision Charts (Forest Hill, Australia). English alphabet charts were
used for literate subjects and E-type charts for illiterate subjects. If visual
acuity was worse than 6/6, objective refraction was performed with a streak
retinoscope (Heine Optotechnik, Herrsching, Germany), followed by assessment of
subjective acceptance by the subject. External eye examination, assessment of
pupillary reaction, and anterior segment examination with a slit-lamp
biomicroscope (Haag-Streit, Koeniz, Switzerland) were performed. Intraocular
pressure was measured with a Goldmann applanation tonometer (Clement Clarke
International, Harlow, UK) in those children who could not sit at the slit lamp
or in debilitated subjects who were examined at home. Gonioscopy was attempted
on all subjects with an NMR-K two-mirror lens (Ocular Instruments, Bellevue,
WA), and the angle was graded as open, occludable, or occluded according to
Scheies classification based on the extent of visible angle structures.24 If gonioscopy
was not possible with a particular patient, the van Herick technique was used
to grade the angle with the slit lamp.25
Dilated
Examination
All subjects had their pupils
dilated unless contraindicated due to risk of angle closure. Tropicamide 1% and
phenylephrine 2.5% were used for subjects >15 years of age, and tropicamide
1% and cyclopentolate 1% were used in subjects =15 years of age. Phenylephrine
was not used if contraindicated. An attempt was made to obtain a pupillary diameter
of 8 mm for lens and posterior segment examination.20 After the
dilatation, the size of the pupil and intraocular pressure were recorded again.
The lens was examined under the slit lamp, and nuclear opacity was graded
according to the Lens Opacities Classification System III (LOCS III)26 : cortical
and posterior subcapsular cataracts were graded using the Wilmer Classification.27
Inter-rater reliability was determined between the study principal investigator
(Lalit Dandona) and the clinicians who were specially trained for slit-lamp
grading of cataract with LOCS III and Wilmer classifications.20 The
details of training and other procedures have been reported elsewhere.20 Those who
graded lens status were masked to the interview data and also the investigators
who administered the questionnaire in the field were masked to the clinical
findings. The possible etiology of cataract was also documented. If the
crystalline (natural) lens was absent, the presence of any lens (aphakia) or
the presence of an intraocular lens (pseudophakia) was determined and
documented. The absence, presence, and clarity of the posterior lens capsule
were determined in aphakic and pseudophakic eyes. Subjects who were physically
unable to come to the clinic were examined at home with portable equipment.
Data
Analysis
Smoking
Status.
For this analysis, subjects were
categorized as never-smokers (never smoked) and ever-smokers (current and prior
smokers). Current and prior smokers (ever smokers) were those for whom smoking
had become a habit and who had smoked for a minimum of at least 1 year.
Subjects who had been smoking for less than 1 year were considered to be
nontobacco smokers (never-smokers).
Cumulative
Smoking Dose.
For this analysis, cigarette and
cigar smokers were classified into light
and heavy smokers. Cigarette smoking subjects were classified based on
cigarette pack-years. Pack-year is a way to measure the amount a person has
smoked over a long period. Cigarette pack-years were calculated by multiplying
the number of packs of cigarettes smoked per day by the number of years the
person had smoked. For example, 1 pack-year is equal to smoking one pack per
day for 1 year, and so on. In this analysis, subjects were considered to be
light smokers if they had <15 cigarette pack-years of smoking (median
cigarette pack-years smoked) and heavy smokers if they had 15 years or more
cigarette pack-years. Cigar-smoking subjects having cigar person-years of
smoking =21 years (median cigar person years smoked) were considered to be
heavy smokers.
Definitions
of Cataract.
We defined the presence of nuclear
cataract (NC) as at least one eye showing nuclear opalescence of grade 3.0 or
higher on LOCS III.28 Cortical
cataract (CC) was considered to be present if at least one eye had a Wilmer
grade =2. Posterior subcapsular cataract (PSC) was considered to be present if
at least one eye had a Wilmer grade =1.
Any
Cataract.
Any cataract (cataract of any type)
was defined as (1) the presence in at least one eye of significant nuclear,
cortical, or posterior subcapsular cataract, as just defined; (2) the presence
of bilateral total cataract; (3) the presence of unilateral total cataract with
phthisis bulbi in the other eye; (4) a history of prior bilateral cataract
surgery (pseudophakia or aphakia); and (5) a history of prior unilateral
cataract surgery (pseudophakia or aphakia) with combination of total cataract
or phthisis bulbi in the other eye.
Of the total 10,293 examined
subjects, data were analyzed for the 7,416 (72%) subjects who were aged =16
years, after excluding from analysis 11 subjects who had traumatic cataract and
4 who had bilateral phthisis bulbi. A total of 2862 subjects, aged =15 years,
were excluded from the analysis. Of the 7416 subjects, it was possible to grade
lens status for 7248 (97.7%) of them. Lens status was not gradable for 168
subjects because of ungradable lens opacities or a history of prior cataract
surgery. Among these, 85 had bilateral cataract surgery (pseudophakia or
aphakia), 7 had bilateral total cataract, 49 had unilateral cataract surgery
(pseudophakia or aphakia) combined with total cataract in the other eye, 4 had
unilateral cataract surgery (pseudophakia or aphakia) with phthisis bulbi in
the other eye, 1 had total cataract with combination of phthisis bulbi in the
other eye, 19 subjects had pupils that could not be dilated because of the risk
of angle closure, and 1 patient did not agree to have her pupils dilated for
religious reasons. Lens grading data were missing for two subjects for unknown
reasons.
Statistical
Analysis.
The prevalence of NC, CC, and PSC
and other estimates in our sample were adjusted for the estimated age and sex
distribution of the population in India during 2000 (http://www.census.gov).
The 95% confidence intervals were calculated by assuming a Poisson distribution29 for prevalence
<1%, and normal approximation of binomial distribution for prevalence of
>1%. The confidence intervals were adjusted for the design effect of the
sampling strategy, which was based on the rates in each cluster.30 The
association between each cataract type and smoking, age, sex, socioeconomic
status, and education was assessed with the ?2 test or Fisher exact
test for univariate analyses, followed by multivariate analyses with multiple
logistic regression. All statistical analyses were performed on computer (SPSS
ver.12.0 for Windows; SPSS, Chicago, IL). We considered a two-tailed P
< 0.05 to be statistically significant for this analysis.
Results
Of a total of 11,786 subjects
sampled for APEDS, 10,293 (87.3%) participated in the study. The participation
rate was 85.4% in the urban area (Hyderabad) and 84.6%, 91.6%, and 87.7% in the
rural areas of West Godavari, Adilabad, and Mahabubnagar districts,
respectively. Data were analyzed for 7416 (72%) subjects who were =16 years of
age, after excluding from the analysis 11 subjects who had traumatic cataract
and 4 with bilateral phthisis bulbi. A total of 4027 (54.3%) were females, 3865
(52.1%) were illiterate persons, and 631 (8.5%) were cigar smokers. Any
cataract was present in 1482 subjects, with an age-gender-areaadjusted
prevalence of 14.4% (95% CI: 13.615.2). A total of 901 subjects had NC =3
(with or without other types, an age-gender-areaadjusted prevalence of 9.2%
[95% CI: 8.59.9]); 541 subjects had CC (alone or with other types, an
age-gender-areaadjusted prevalence of 5.5% [95% CI: 5.26.2]); and 569
subjects had PSC, an age-gender-areaadjusted prevalence of 6.0% (95% CI:
5.46.5). Table 1 shows the
prevalence of all grades of nuclear, cortical, and poster subcapsular lens
opacities and pure and mixed types of opacities. The univariate distribution of
type of cataract and prevalence of prior cataract surgery and/or total cataract
for the demographic variables, history of various forms of smoking, and mixed
smoking is shown in Table 2 . The
multivariate logistic regression analysis assessing the association with any
cataract and specific cataract types is shown in Tables
3 and
4 , respectively. A history of prior
cataract surgery and/or total cataract was present in 146 (1.97%) of the
subjects, including 85 (1.15%) persons in whom bilateral prior cataract surgery
(pseudophakia or aphakia) had been performed. The presence of history of prior
cataract surgery and/or total cataract increased significantly with increasing
age (Table 2) .
All types of cataracts were seen to increase significantly with increasing age
and decreasing socioeconomic status. The univariate associations of NC, CC, and
PSC were significantly higher among mixed smokers of one form or more than one
form of smoking compared with never-smokers.
View this table:
Table 1.
Prevalence of Lens Opacities among
Subjects Aged 16 Years or More by Type of Cataract and Severity
View this table:
Table 2.
Univariate Effect of Demographic
Variables and Type of Smoking on Nuclear, Cortical, Posterior Subcapsular
Cataract, Prior Cataract Surgery, and/or Total Cataract
View this table:
Table 3.
Adjusted Effect of Demographic
Variables with Smoking Status on Any Cataract by Multivariate Logistic
Regression Analysis
View this table:
Table 4.
Association of Smoking History with
Nuclear, Cortical, and Posterior Subcapsular Cataracts and Prior Cataract
Surgery and/or Total Cataract by Multivariate Logistic Regression Analysis
Multivariate logistic regression
analysis revealed that, after adjusting for demographic factors and for history
of smoking, the prevalence of any cataract significantly increased with
increasing age and was significantly higher in females, in the extremely low
socioeconomic group, and in illiterate persons (Table
3) . The prevalence of any cataract
was significantly higher in cigarette and cigar smokers but not in beedi and
hookah smokers.
The results of four separate
multivariate logistic regression models after adjusting for demographic factors
are presented in Table 4 . We found
that cigarette smoking was significantly associated with cortical cataract and
history of prior cataract surgery and/or total cataract, adjusted OR = 2.10
(95% CI: 1.352.91) and 1.98 (95% CI: 1.053.70), respectively. An adjusted OR
of 1.55 (95% CI: 1.162.01) for cigar smokers was noted, compared with
never-smokers (Table 4) .
Table 4 points to the
association of cumulative smoking dose with the risk of specific cataract type,
after adjusting for age, gender, socioeconomic status, and education. There was
evidence of a doseresponse pattern for cigarette and cigar smoking. Corresponding
to the cumulative smoking dose, the odds of NC, CC, and a history of prior
cataract surgery and/or total cataract were seen to be significantly higher
among cigarette smokers who smoked heavily (adjusted OR for NC = 1.65. 95% CI:
1.102.59; for CC = 2.11, 95% CI: 1.383.24; and for prior cataract surgery
and/or total cataract = 2.10; 1.054.22). We also found the prevalence of NC to
be significantly higher among cigar smokers who smoked heavily (adjusted OR =
1.50, 95% CI: 1.101.95) compared with never-smokers. Higher odds of CC were
noted in heavy smokers of cigarettes and cigars, but did not reach statistical
significance in the multivariate analyses.
Discussion
Types
of Cataract and Etiology
Accurate population-based data on
the risk factors and various features of blindness are necessary, particularly
in a country such as India, which has a large cataract burden. Our results
showed a significantly higher prevalence of NC in this population, and
approximately 78% of this prevalence was in the rural areas (data not shown).
These results suggest that after adjustment for demographic factors, any
cataract significantly increased with increasing age. There was a significantly
higher prevalence of any cataract in females, illiterate persons, the extremely
low socioeconomic group, and cigarette and cigar smokers (Table
3) . Several population-based studies
have found a higher prevalence of both nuclear and cortical opacities in women.31 32 33 The
association between education and cataract has also been one of the most
consistently reported observations in the epidemiologic studies of cataract.9 34 35 36 37 Our study results
suggest that low socioeconomic status is a risk factor for cataract. This
finding of an association between low socioeconomic status and lens changes has
been supported by other studies.38 39 40 41 42
There is a growing consensus that
smoking increases the risk of nuclear cataract. Association between cigarette
smoking and cortical cataract also has recently been reported.37 43 44 Our study is
consistent with previous studies in finding that cigarette and cigar smokers
are at a higher risk of development of nuclear and cortical cataract.
Consistent with other studies, our data suggest that NC is more strongly
associated with cigar smoking.8 Contradictory
to some studies,9 36 45 but favoring
others,37 43 44 our study
showed that prevalence of CC is significantly higher in the subjects with
history of cigarette smoking (Table
4) .
Our study showed that the cumulative
smoking dose of cigarettes plays a significant role in accounting for higher
prevalence of NC and CC in this population. The finding of a higher prevalence
of CC in heavy cigarette smokers is in accordance with previous findings from
India.37 We also found
a higher prevalence of prior cataract surgery to be significantly associated
with lifelong cigarette smokers who smoked heavily compared with never-smokers.
However, heavy cigar smoking was more strongly associated with NC but not with
other types. Higher prevalence of PSC was present in both heavy cigarette and
cigar smoking, but it did not reach statistical significance.
The situation with beedi smoking was
less clear, because there were more beedi smokers than cigarette smokers (23.9%
vs. 13.3%) and yet the cataract risk for the former appeared to be less. The
odds ratio was almost significant for a reduced effect (OR = 0.81). We
speculate that this difference may have to do with the relative inhalation
dosages. A typical beedi smoker smokes a pack of 24 beedis per day. Each beedi
weighs approximately 0.36 g and contains 0.15 g of tobacco loosely wrapped in a
leaf that weighs ~0.16 g. In contrast, a typical cigarette smoker smokes a
pack of 20, each weighing approximately 0.82 g and containing 0.70 g of tobacco
wrapped in paper. The daily inhalation dosage for a cigarette smoker is thus
four to five times higher. Local cigars (chutta) are bits of tobacco
wrapped tightly with tobacco leaves, weighing approximately 2 to 3 g each, and
a typical smoker smokes five a day. The inhalation dose is approximately the
same as that of cigarettes and far higher than that of beedis.
Mechanisms
of Smoke Action
The mechanisms by which smoking may
damage the lens are becoming increasingly clear. Damage appears not to be
related to the nicotine in tobacco, but more generally and commonly, to any
form of smoke and partially pyrolyzed organic material from tobacco, coal,
wood, cooking fuel, or automobile fuel. Our earlier studies14 suggest the
major damaging mechanism to be oxidative stress brought about by reactive
oxygen species (ROS) generated by smoke constituents both in the dark and in
light. Damage is more likely to occur through systemic absorption of smoke
constituents that reach the lens and generate ROS endogenously through
photodynamic action. This effect would depend on the amount of such photoactive
material in the lens and is therefore thought to be dose-dependent (heaviness
and period of smoke inhalation). In prior smokers who have overcome the habit,
such deposition of photodynamic material would have ceased, rendering this mode
of oxidative stress inoperative. This would explain why quitting smoking
reduces this risk factor.46 47
That oxidative stress by smoke is
generated in dark conditions, as suggested by reports15 16 48 49 on the
accumulation of metals such as Cd and Fe and the reduction in levels of vitamin
C in the lens and blood of smokers (and smoke-exposed rats). Oxidative stress
occurs through a metal-catalyzed Fenton reaction that produces ROS and by
modulating the role of metallothioneins. Partial relief of the condition by the
administration of the antioxidant vitamin E and the iron-chelator deferoxamine48 49 adds support
to the idea that oxidative stress is imposed by smoke. The recent French
Age-Related Eye Diseases (POLA) study31 implicates the
role of antioxidant enzymes in the etiology of PSC in lifelong heavy smokers.
Possible
Causes of Gender-Based Differential Risk
Our study shows that the prevalence
of NC, CC, and PSC is higher among females compared with males, in accordance
with some earlier reports.32 34 50 51 52 53 54 It is quite
possible that this higher prevalence of cataract in women in the present
instance is related to gender-based differences in exposure to the environment and/or
to hormonal influences associated with menopause.55 56 It could also
be because most rural women tend to use cheap cooking fuels (e.g., dried wood,
twigs and sticks, leaves, cow dung), which produce a lot of smoke. Prolonged
exposure to this smoke (particularly in ill-ventilated spaces) would serve as
an additional and cumulative source of oxidative damage to the eye. That such
cooking smoke could be a risk factor has been alluded to earlier.14 57 Added to this
is the fact that most women in AP, particularly in rural areas, are anemic,58 and of
subnormal nutritional status,57 which too may
be confounding factors in increasing the risk of cataract.
This study has a few limitations as
well as strengths. Because this was a cross-sectional study, there may be a
potential for recall bias that might have affected the results. Cataract is a
multifactorial disease and, as we did not study all other confounding factors,
such as presence of diabetes, steroid intake, exposure to sunlight, and diet,
we may have underestimated the adjusted effect of smoking on the risk of
cataract. In contrast, a strength of the study is that we had a participation
rate of more than or equal to 85% in all the selected areas, which means the
sample roughly represents the entire the population of AP.
In summary, the findings of this
study indicate that prevalence of cataract increased with increasing age and
was more common among females, illiterate persons, and the extremely low
socioeconomic group. Our results confirmed previous findings of higher
prevalence of NC and CC in those who smoke cigarettes heavily and also suggest
that there is a higher prevalence of NC in cigar smokers. Our results also
proved that a higher prevalence of history of prior cataract surgery occurred
more commonly among those with a history of heavy cigarette smoking, suggesting
that an early onset of cataract may be possible in those who had a lifelong
habit of heavy cigarette smoking. Our results suggest that because smoking
remains a modifiable risk factor for cataract, an effective antismoking program
in India may decrease the large burden of cataract blindness to some extent. In
addition, it would have a potentially beneficial impact on respiratory and
cardiovascular health. It would make sense to extend the antismoking awareness
program to schools. Educating about the ill effects of tobacco smoking may go a
long way in promoting healthy behavior among the general population, in
particular the younger generation, with a view toward reducing tobacco-related
ailments, including cataract.
Acknowledgments
The authors thank the APEDS team, in
particular, Lalit and Rakhi Dandona, who designed and conducted the detailed
study; Marmamula Srinivas, Vallam S. Rao, Rohit Khanna, and Rajesh Kumar for
clinical input; and the volunteers for participating in the study.
Footnotes
- Presented at the 12th World Conference on Tobacco or
Health, Helsinki, Finland, August 38, 2003. - Supported by grants from the
Christoffel-Blindenmission, Bensheim, Germany, and the Hyderabad Eye
Research Foundation, Hyderabad, India. - Submitted for publication January 29, 2004; revised
June 14, August 20, and September 23, 2004; accepted September 26, 2004. - Disclosure: S. Krishnaiah, None; K. Vilas,
None; B.R. Shamanna, None; G.N. Rao, None; R. Thomas,
None; D. Balasubramanian, None - The publication costs of this article were defrayed in
part by page charge payment. This article must therefore be marked advertisement
in accordance with 18 U.S.C. §1734 solely to indicate this fact. - Corresponding author: Sannapaneni Krishnaiah,
International Centre for the Advancement of Rural Eye Care (ICARE), L. V.
Prasad Eye Institute, Banjara Hills, Hyderabad 500 034, India; krishnaiah@lvpei.org.
- Copyright 2005 The Association for Research in Vision
and Ophthalmology, Inc.
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