Smoking and its association with cataract: results of the Andhra Pradesh eye disease study from India.
ABSTRACT To investigate the associations between tobacco smoking and various forms of cataracts among the people of a state in India.
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.
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]: 1.24-1.96), 1.46 (95% CI: 1.17-1.70), and 1.92 (95% CI: 1.14-3.24), respectively. After adjustment, cigarette and cigar smokers had a significantly higher prevalence of any cataract, adjusted OR=1.51 (95% CI: 1.10-2.06) and 1.44 (95% CI: 1.12-1.84), 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 dose-response 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: 1.10-2.59), cortical cataract (OR=2.11; 95% CI: 1.38-3.24), and history of prior cataract surgery and/or total cataract (OR=2.10; 95% CI: 1.05-4.22). Nuclear cataract was significantly higher in cigar smokers (adjusted OR=1.55; 95% CI: 1.16-2.01) and in cigar smokers who smoked heavily (>21 person-years of smoking; OR=1.50; 95% CI: 1.10-1.95), compared with never-smokers.
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.
- SourceAvailable from: who.int[show abstract] [hide abstract]
ABSTRACT: Cataract prevalence increases with age. As the world's population ages, cataract-induced visual dysfunction and blindness is on the increase. This is a significant global problem. The challenges are to prevent or delay cataract formation, and treat that which does occur. Genetic and environmental factors contribute to cataract formation. However, reducing ocular exposure to UV-B radiation and stopping smoking are the only interventions that can reduce factors that affect the risk of cataract. The cure for cataract is surgery, but this is not equally available to all, and the surgery which is available does not produce equal outcomes. Readily available surgical services capable of delivering good vision rehabilitation must be acceptable and accessible to all in need, no matter what their circumstances. To establish and sustain these services requires comprehensive strategies that go beyond a narrow focus on surgical technique. There must be changes in government priorities, population education, and an integrated approach to surgical and management training. This approach must include supply of start-up capital equipment, establishment of surgical audit, resupply of consumables, and cost-recovery mechanisms. Considerable innovation is required. Nowhere is this more evident than in the pursuit of secure funding for ongoing services.Bulletin of the World Health Organisation 02/2001; 79(3):249-56. · 5.25 Impact Factor
- Community eye health / International Centre for Eye Health 02/1998; 11(25):1-3.
- [show abstract] [hide abstract]
ABSTRACT: Cataracts, the world's leading cause of blindness, are an enormous public health problem in both developing and industrialized countries. Identifying the risk factors responsible for cataract formation is a difficult and complicated problem because a realistic causal model in cataract formation would not be a simple linear sufficient cause paradigm (e.g., one exposure-one cataract type). A more complex model depicting each risk factor as a component cause, or part of a sufficient cause such as the sufficient/component cause model proposed by Rothman (62), is a more realistic way to summarize how multiple risk factors act in cataract etiology. Moreover, even this model has shortcomings, especially in explaining cataract etiology. It ignores the obvious importance of time to cataract formation and the way different component causes may act on different etiologic branches of cataract formation, e.g., nuclear sclerosis, posterior subcapsular cataracts, and mixed. Despite the complexity in identifying cataract risk factors, attempting to do so provides new hope in dealing with the morbidity, mortality, and cost of this disease. The evidence is overwhelming that age, trauma, and intraocular inflammation are important cataract risks. However, these exposures either are inevitable or are not major contributors to the population attributable risk. On the basis of both coherence and predictive performance, undernutrition is an important risk factor that can be altered. However, work still needs to be done in two areas related to this risk. First, regarding individuals in developing nations, the question must be asked about which nutrients (or lack thereof) are the culprits. The epidemiologic evidence that antioxidants are the missing nutrients is far from overwhelming. For developed nations, the obvious question still to be answered is whether the results of the Linxian Cataract Studies (11) and the India-US Case-Control Study (12) can be generalized to industrial nations. To help answer this question, an intervention study sponsored by the National Institutes of Health is now underway (K. Kupfer, Director, National Eye Institute of the USA, Bethesda, Maryland, personal communication, 1993). Ultraviolet radiation, especially ultraviolet B radiation, is an important risk for cortical cataracts, and one study (27) has even demonstrated a dose-response relation. However, the public health implication of this finding is not clear. Isolating the risk of ultraviolet B radiation exposure as a cause of cortical cataracts (and, in general, not of other types) indicates that the risk is small on a public health scale. This is because cortical cataracts are well tolerated and frequently require no treatment at all. The evidence that links ultraviolet B radiation to other cataract types comes mainly from ecologic studies and needs to be verified by analytic studies that are specifically designed to study the association. The strength of the association, consistency of studies, coherence, and biologic plausibility all indicate that both systemic and topical steroids are significant risk factors for the formation of posterior subcapsular cataracts. Given that most people are not chronic steroid users, the population attributable risk is low; however, the relative risk of those unfortunate enough to require chronic steroid use is high. The evidence is accumulating that cataracts can be added to the list of illnesses that are at least partially attributed to smoking. Although consistency among studies has not been obtained, this is certainly a plausible cause, and dose-response relations have been demonstrated (53). At this point, nuclear sclerosis is the most important cataract type associated with smoking. More work needs to be done to assess the role of smoking on other cataract types and to assess the risk of those who stop smoking. Retrospective studies that examine diabetes as a risk for cataracts are almost inevitably marred by hte selection biaEpidemiologic Reviews 02/1995; 17(2):336-46. · 9.27 Impact Factor
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
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 demo-
graphic factors and for history of smoking, females, illiterate
persons, and those belonging to the extreme lower socioeco-
nomic status group were found to have a significantly higher
prevalence of any cataract, adjusted odds ratio (OR) ? 1.60
(95% confidence interval [CI]: 1.24–1.96), 1.46 (95% CI: 1.17–
1.70), and 1.92 (95% CI: 1.14–3.24), respectively. After adjust-
ment, cigarette and cigar smokers had a significantly higher
prevalence of any cataract, adjusted OR ? 1.51 (95% CI: 1.10–
2.06) and 1.44 (95% CI: 1.12–1.84), respectively, compared
with those who had never smoked (“never-smokers”). A signif-
icantly higher prevalence of nuclear, cortical cataract, and
history of prior cataract surgery and/ or total cataract was
found among cigarette smokers. A dose–response 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: 1.10–2.59), cortical cataract (OR ? 2.11; 95% CI:
1.38–3.24), and history of prior cataract surgery and/or total
cataract (OR ? 2.10; 95% CI: 1.05–4.22). Nuclear cataract was
significantly higher in cigar smokers (adjusted OR ? 1.55; 95%
CI: 1.16–2.01) and in cigar smokers who smoked heavily (?21
person-years of smoking; OR? 1.50; 95% CI: 1.10–1.95), com-
pared 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. (Invest Ophthalmol Vis
Sci. 2005;46:58–65) DOI:10.1167/iovs.04-0089
prevent or delay cataract formation, and treat that which does
occur.1Although 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 expec-
tancy. Although surgery is the only effective treatment option
available, identifying risk factors may help to establish preven-
tive 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.2In 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.3Intervention against cataract blindness has received
priority attention in the global initiative called VISION 2020:
The Right to Sight.4–6
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 blind-
ness.8Several studies9–19have investigated and reported the
significant relationship between cigarette smoking and an in-
creased risk of cataract development. Despite the multifactorial
etiology of these ocular syndromes, smoking is an independent
risk factor that has dose–response effects. It causes morpho-
logic and functional changes to the lens and retina due to its
atherosclerotic and thrombotic effects on the ocular capillar-
ies. In addition, evidence exists that cigarette smokers are
more at risk of development of cataract at an earlier age than
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 country’s 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.
ataract is a major cause of avoidable blindness and visual
impairment throughout the world. The challenges are to
From the L. V. Prasad Eye Institute, Hyderabad, India.
Presented at the 12th World Conference on Tobacco or Health,
Helsinki, Finland, August 3–8, 2003.
Supported by grants from the Christoffel-Blindenmission, Ben-
sheim, Germany, and the Hyderabad Eye Research Foundation, Hyder-
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. Sha-
manna, None; G.N. Rao, None; R. Thomas, None; D. Balasubra-
The publication costs of this article were defrayed in part by page
charge payment. This article must therefore be marked “advertise-
ment” 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;
Investigative Ophthalmology & Visual Science, January 2005, Vol. 46, No. 1
Copyright © Association for Research in Vision and Ophthalmology
SUBJECTS AND METHODS
The details of various aspects of design of the APEDS have been
described previously.3,20–22Approval 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 urban–rural 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 socio-
economic 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 socioeco-
nomic strata were extreme low (monthly income per person, ? 200
rupees (US$ 4.31), low (201–500 rupees), middle (501–2000 rupees),
and high (?2000 rupees). We assumed that 0.7% of the Hyderabad
population was homeless (no accurate data were available) and in-
cluded those people in the lowest socioeconomic stratum. We strati-
fied 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 ran-
domly 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
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 popula-
tion 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 socio-
economic strata in these rural areas.
The volunteers were interviewed in detail by trained field investiga-
tors.20A 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 vol-
unteer 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 question-
naire. 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.
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 refrac-
tion, 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 refrac-
tion was performed with a streak retinoscope (Heine Optotechnik,
Herrsching, Germany), followed by assessment of subjective accep-
tance by the subject. External eye examination, assessment of pupillary
reaction, and anterior segment examination with a slit-lamp biomicro-
scope (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
Scheie’s 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
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.20After
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 Classifica-
tion System III (LOCS III)26: cortical and posterior subcapsular cata-
racts were graded using the Wilmer Classification.27Inter-rater reliabil-
ity 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.20The
details of training and other procedures have been reported else-
where.20Those 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
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 non–tobacco smokers (never-
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-
IOVS, January 2005, Vol. 46, No. 1
Association of Smoking with Cataract59
year is a way to measure the amount a person has smoked over a long
period. Cigarette pack-years were calculated by multiplying the num-
ber 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.28Cortical 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 (pseu-
dophakia or aphakia), 7 had bilateral total cataract, 49 had unilateral
cataract surgery (pseudophakia or aphakia) combined with total cata-
ract 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
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 assum-
ing a Poisson distribution29for prevalence ?1%, and normal approxi-
mation 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.30The association be-
tween each cataract type and smoking, age, sex, socioeconomic status,
and education was assessed with the ?2test 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.
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 Ma-
habubnagar 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-area–adjusted prevalence of 14.4% (95% CI:
13.6–15.2). A total of 901 subjects had NC ?3 (with or without
other types, an age-gender-area–adjusted prevalence of 9.2%
[95% CI: 8.5–9.9]); 541 subjects had CC (alone or with other
types, an age-gender-area–adjusted prevalence of 5.5% [95% CI:
5.2–6.2]); and 569 subjects had PSC, an age-gender-area–ad-
justed prevalence of 6.0% (95% CI: 5.4–6.5). Table 1 shows the
prevalence of all grades of nuclear, cortical, and poster sub-
capsular 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 demo-
graphic 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, respec-
tively. 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 (pseu-
dophakia 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.
TABLE 1. Prevalence of Lens Opacities among Subjects Aged 16
Years or More by Type of Cataract and Severity
Type of Cataract/Lens Grade
Posterior subcapsular opacity
Pure posterior subcapsular
n ? 7248.
* Mixed cataract includes a combination of nuclear, cortical, or
posterior subcapsular cataract. Pure nuclear, cortical, and posterior
subcapsular cataract subgroups have isolated cataracts without the
presence of the other types. The opacity grade of the worse eye was
considered for analysis.
† Data were analyzed for persons ?16 years of age with gradable
60Krishnaiah et al.
IOVS, January 2005, Vol. 46, No. 1
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
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:
1.35–2.91) and 1.98 (95% CI: 1.05–3.70), respectively. An ad-
justed OR of 1.55 (95% CI: 1.16–2.01) for cigar smokers was
noted, compared with never-smokers (Table 4).
TABLE 2. Univariate Effect of Demographic Variables and Type of Smoking on Nuclear, Cortical, Posterior Subcapsular Cataract, Prior Cataract
Surgery, and/or Total Cataract
(n ? 7416)*
Sx and/or TC
LPG, biogas, and kerosene
Use of cheaper cooking fuel
Never a smoker
Never a smoker
Never a smoker
Never a smoker
Never a smoker
Only one form of smoking
More than one form of smoking
0/3 (0.0) 3
Data are expressed as the number of persons/total group (percentage of total group). Sx, surgery; TC, total cataract.
* Data were analyzed for n ? 7416 subjects and excluded the data from 11 subjects who had a diagnosis of traumatic cataract and from 4
subjects who had bilateral phthisis bulbi.
† Data were analyzed for n ? 7248 subjects ?16 years of age with gradable cataracts. Data on 13 subjects for CC and 11 subjects for PSC were
not available (unknown reason).
‡ ?2test: P ? 0.0001 for NC, P ? 0.0001 for CC, P ? 0.0001 for PSC, and P ? 0.0001 for any prior cataract Sx and/or TC.
§ Fisher exact test: P ? 0.592 for NC, P ? 0.005 for CC, P ? 0.483 for PSC, and P ? 0.616 for any prior cataract Sx and/or TC.
?Fisher exact test: P ? 0.0001 for NC, P ? 0.280 for CC, P ? 0.032 for PSC, and P ? 0.167 for any prior cataract Sx and/or TC. Data on type
of fuel mainly used for cooking were available for 3161 (78.5%) of the female population. Cheaper cooking fuels include wood, coal, cow dung,
¶ ?2test: P ? 0.0001 for NC, P ? 0.359 for CC, P ? 0.004 for PSC, and P ? 0.084 for any prior cataract Sx and/or TC. Socioeconomic status
was defined according to monthly per capita income in Indian rupees: ?200, extreme lower; 201–500 lower; 501–2000, middle; and ?2000 upper.
Data on socioeconomic status were not available for 124 subjects.
# Fisher exact test: P ? 0.0001 for NC, P ? 0.0001 for CC, P ? 0.0001 for PSC, and P ? 0.012 for any prior cataract Sx and/or TC. Data on
education were not available for eight subjects.
** Fisher exact test: P ? 0.248 for NC, P ? 0.105 for CC, P ? 0.359 for PSC, and P ? 0.205 for any prior cataract Sx and/or TC.
†† Fisher exact test: P ? 0.0001 for NC, P ? 0.0001 for CC, P ? 0.0001 for PSC, and P ? 0.112 for any prior cataract Sx and/or TC.
‡‡ Fisher exact test: P ? 0.0001 for NC, P ? 0.901 for CC, P ? 0.001 for PSC, and P ? 0.296 for any prior cataract Sx and/or TC.
§§ Fisher exact test: P ? 0.042 for NC, P ? 0.208 for CC, P ? 1.000 for PSC, and P ? 1.000 for any prior cataract Sx and/or TC.
?? ?2test: P ? 0.0001 for NC, P ? 0.018 for CC, P ? 0.0001 for PSC, and P ? 0.602 for any prior cataract Sx and/or TC.
IOVS, January 2005, Vol. 46, No. 1
Association of Smoking with Cataract 61
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 dose–response 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 cig-
arette smokers who smoked heavily (adjusted OR for NC ?
1.65. 95% CI: 1.10–2.59; for CC ? 2.11, 95% CI: 1.38–3.24;
and for prior cataract surgery and/or total cataract ? 2.10;
1.05–4.22). We also found the prevalence of NC to be signif-
icantly higher among cigar smokers who smoked heavily (ad-
justed OR ? 1.50, 95% CI: 1.10–1.95) 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.
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 popu-
lation, and approximately 78% of this prevalence was in the
TABLE 3. Adjusted Effect of Demographic Variables with Smoking Status on Any Cataract by Multivariate Logistic Regression Analysis
Demographic Factors, Smoking StatusTotal Population*
Odds Ratio (95% CI)
for Any Cataract
LPG, biogas, and kerosene
Use of cheaper cooking fuel
Never a smoker
Only one form of smoking
More than one form of smoking
1.01 (0.51–1.70) 0.896
1.17 (0.95–1.47) 0.150
1.51 (1.10–2.06) 0.013
1.44 (1.12–1.84) 0.004
36.26 (0.19–211.97) 0.307
* Data were analyzed for n ? 7416 subjects and excluded from analysis on 11 subjects who had a diagnosis of traumatic cataract and on 4
subjects with bilateral phthisis bulbi.
† Nuclear, cortical, or posterior subcapsular cataracts, including 85 subjects with bilateral prior cataract surgery (pseudophakic or aphakic),
7 with bilateral total cataract, 53 with unilateral cataract surgery (pseudophakic or aphakic) combined with total cataract or phthisis bulbi in the
other eye, and 1 with total cataract combined with phthisis bulbi in the other eye.
‡ Data on type of fuel mainly used for cooking were available for 3161 (78.5%) of the female population, and this variable was replaced in the
multivariate analysis adjusting for age, socioeconomic status, smoking status, and education. Cheaper cooking fuels used include wood, coal, and
§ Socioeconomic status defined according to monthly per capita income in Indian rupees: ?200, extreme lower; 201–500, lower; 501–2000,
middle; and ?2000, upper. Data on socioeconomic status were not available for 124 subjects.
? Data on education were not available for eight subjects.
¶ Smoking of cigarette, beedi, cigar, or hookah. Variables: cigarette, cigar, beedi, and hookah smoking were replaced respectively with any
smoking variable in the logistic regression model.
62Krishnaiah et al.
IOVS, January 2005, Vol. 46, No. 1
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 opaci-
ties in women.31–33The association between education and
cataract has also been one of the most consistently reported
observations in the epidemiologic studies of cataract.9,34–37
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 sup-
ported by other studies.38–42
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.8Contradictory to some studies,9,36,45but favoring
others,37,43,44our study showed that prevalence of CC is sig-
nificantly higher in the subjects with history of cigarette smok-
ing (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.37We 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
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 approx-
imately 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 ap-
proximately 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 studies14suggest 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 absorp-
tion 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 (heavi-
ness 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 condi-
tions, as suggested by reports15,16,48,49on 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 reac-
tion that produces ROS and by modulating the role of metal-
lothioneins. Partial relief of the condition by the administration
of the antioxidant vitamin E and the iron-chelator deferox-
amine48,49adds support to the idea that oxidative stress is
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
OR (95% CI)
OR (95% CI)
OR (95% CI)
OR (95% CI) for Prior
Cataract Sx and/or TC*
Cumulative smoking dose‡
Cumulative smoking dose‡
1.25 (0.85–1.84)2.10 (1.35–2.91) 1.01 (0.66–1.53)1.98 (1.05–3.70)
1.00 1.001.00 1.00
1.001.00 1.00 1.00
1.55 (1.16–2.01)0.92 (0.70–1.23)1.00 (0.73–1.32) 0.62 (0.33–1.15)
ORs and 95% CIs were adjusted for age, gender, socioeconomic status, and education. Sx, surgery; TC, total cataract.
* Data were analyzed for n ? 7416 subjects and excluded from analysis on 11 subjects who had a diagnosis of traumatic cataract and on four
subjects with bilateral phthisis bulbi.
† Data were analyzed for n ? 7248 subjects ?16 years of age with gradable cataract lens. Data on 13 subjects for CC and on 11 subjects for
PSC were not available (unknown reason).
‡ This variable was replaced with the respective smoking status variable in the multivariate logistic regression model.
IOVS, January 2005, Vol. 46, No. 1
Association of Smoking with Cataract63
imposed by smoke. The recent French Age-Related Eye Dis-
eases (POLA) study31implicates the role of antioxidant en-
zymes 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.32,34,50–54It 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 envi-
ronment and/or to hormonal influences associated with meno-
pause.55,56It 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 oxida-
tive damage to the eye. That such cooking smoke could be a
risk factor has been alluded to earlier.14,57Added to this is the
fact that most women in AP, particularly in rural areas, are
anemic,58and of subnormal nutritional status,57which 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 con-
founding 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 preva-
lence 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 oc-
curred 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 anti-
smoking 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 aware-
ness 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.
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.
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Association of Smoking with Cataract65