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w2 Age-Related Eye Disease Study Research Group. Risk factors associated with age-related nuclear and cortical cataract. A case-control study in the age-related eye disease study, AREDS Report No 5. Ophthalmology 2001;108:1400-8.
w3 Vestergaard P. Smoking and thyroid disorders—a meta-analysis. Eur J Endocrinol 2002;146:153-61.
w4 Hill AB. The environment and disease: association or causation? Proc Royal Soc Med 1965;58:295-300.
w5 Doll R, Peto R, Wheatley K, Gray R, Sutherland I. Mortality in relation to smoking: 40 years’ observations on male British doctors. BMJ 1994;309:901-11.
w6 Department of Health. Survey for England 1998: cardiovascular disease. Department of Health London: 1999. www.archive.official-documents.co.uk/document/doh/survey98/hset3-13.htm (accessed 9 Jan 2004).
w7 Office for National Statistics. Census 2001. First results on population for England and Wales. The Stationery Office London: 2002. Also available at www.statistics.gov.uk/census2001/pop2001/united_kingdom.asp (accessed 9 Jan 2004).
w8 West R, McNeill A, Raw M. Smoking cessation guidelines for health professionals: an update. Thorax 2000;55:987-99.
w9 Wilson N, Hodgen E, Mills J, Wilson G, Field A, Thomson G. Journal article on smoking and blindness prompts significantly more calls to Quitline. N Z Med J 2002;115:199-200.
w10 Devlin EM, Anderson S, Hastings GB, Rautalahti M, Ratte S, Beck
V, et al. Targeting on-pack messages: European smokers’ response.
12th World Conference on Tobacco or Health, Helsinki, Finland 2003. Abstract
No 2996. www.cartesian-secure.com/wctoh/iAbstract/absPrinterPreview.asp?from=iPlanner&aid=80CB479D7DDD40EA8F29C0F32F00A249&sid
(accessed 23 Dec 2003).
Table 1. AMD with and without blindness in UK attributable to smoking.
AMD cases with visual impairment or blindness in UK residents aged >69 years = 202,800
AMD cases with visual impairment or blindness attributable to smoking in UK residents aged >69 years = 53,900
(Cases rounded to nearest 100)
|
|
|
|
|
|
|
Current-smokers |
Ex-smokers |
All smoking status |
|
|
|
|
| Male | ||||||||||||
| 70–74 |
1,059,151
|
0.27
|
0.06
|
0.18
|
0.54
|
0.24
|
0.12
|
0.37
|
2900
|
1000
|
600
|
200
|
| 75–79 |
817,711
|
1.19
|
0.36
|
0.09
|
0.62
|
0.13
|
0.16
|
0.29
|
9700
|
2800
|
2900
|
900
|
| 80–84 |
482,697
|
2.74
|
0.84
|
0.09
|
0.62
|
0.13
|
0.16
|
0.29
|
13200
|
3900
|
4100
|
1200
|
| 85–89 |
226,833
|
4.74
|
3.33
|
0.09
|
0.62
|
0.13
|
0.16
|
0.29
|
10800
|
3100
|
7600
|
2200
|
| ³ 90 |
83,202
|
9.18
|
6.12
|
0.09
|
0.62
|
0.13
|
0.16
|
0.29
|
7600
|
2200
|
5100
|
1500
|
| Subtotal M |
2,669,594
|
44,200
|
13000
|
20,300
|
6000
| |||||||
| Female | ||||||||||||
| 70–74 |
1,280,080
|
0.27
|
0.06
|
0.19
|
0.33
|
0.26
|
0.08
|
0.34
|
3500
|
1200
|
800
|
300
|
| 75–79 |
1,149,218
|
1.19
|
0.36
|
0.1
|
0.33
|
0.16
|
0.09
|
0.25
|
13700
|
3400
|
4100
|
1000
|
| 80–84 |
830,850
|
2.74
|
0.84
|
0.1
|
0.33
|
0.16
|
0.09
|
0.25
|
22800
|
5700
|
7000
|
1700
|
| 85–89 |
525,954
|
4.74
|
3.33
|
0.1
|
0.33
|
0.16
|
0.09
|
0.25
|
2500
|
6200
|
17500
|
4400
|
| ³ 90 |
288,067
|
9.18
|
6.12
|
0.1
|
0.33
|
0.16
|
0.09
|
0.25
|
26400
|
6600
|
17600
|
4400
|
| Subtotal F |
4,074,169
|
91,300
|
23100
|
47,000
|
11800
| |||||||
| Total |
6,743,763
|
135,500
|
36100
|
67,300
|
17800
|
Sources of data
1. Smith W, Assink J, Klein R, Mitchell P, Klaver CCW, Klein BEK, et al. Risk factors for age-related macular degeneration. Pooled findings from three continents. Ophthalmology 2001; 108:697-704.
9. Owen CG, Fletcher AE, Donoghue M, Rudnicka AR. How big is the burden of visual loss caused by age-related macular degeneration in the United Kingdom? Br J Ophthalmol 2003; 87:312-7.
W6. Health Survey for England 1998: cardiovascular disease. London: Department of Health 1999.http://www.archive.official-documents.co.uk/document/doh/survey98/hset3-13.htm (Accessed June 2003).
W7. Office for National Statistics. http://www.statistics.gov.uk/census2001/pop2001/united-kingdom.asp (accessed June 2003).
We calculated the Population Attributable Risk (PAR) for smoking and prevalence of AMD using the formula relating to polytomous variables (see: Hanley JA. A heuristic approach to the formulas for population attributable fraction. J Epidemiol Community Health 2001;55:508-514).
PAR = (Pr current smoking) x (RR current smoking –1) + (Pr ex-smoker) x (RR ex-smoker – 1) / 1 + [(Pr current smoking) x (RR current smoking –1) + (Pr ex-smoker) x (RR ex-smoker – 1)]
Where Pr = prevalence and RR = relative risk.
Estimates of the UK population of blind and visual impaired residents >69 years in 2001 were obtained.w7,9 For the association of AMD with tobacco smoking, we used the pooled analysis from three major populations in the Beaver Dam Eye Study (USA), the Blue Mountains Eye Study (Australia) and the Rotterdam Eye Study (Netherlands)1 The Odds Ratios (OR) in the pooled data from these three populations were 3.12 for current smokers and 1.36 for ex-smokers.1 Self-reportedsmoking status of UK residents as either current-smoker, ex-smoker or never-smoker from the 1998 Health Survey for Englandw6 was used in the analysis.
Definition of blindness: Better eye visual acuity <3/60 Snellen9
Definition of visual impairment: Best visual acuity 6/18–3/60 Snellen9
Data are presented stratified by 5-year age groups. In the 1998 Health Survey for England (HSE), smoking status by gender is provided in 10-year age strata up to age 75 years and for all persons 75 years. We have assumed that 70–74 year olds have the same smoking prevalence as the HSE 65–74 years strata and that all age groups above 75 years have the >75 years smoking prevalence from the HSE. Our estimate is likely to be an underestimate of the total smoking attributable disease burden, as we did not calculate the number of AMD cases in individuals aged <70 years because of imprecise prevalence estimates in younger age groups,9 and because smokers develop AMD at an earlier age than non-smokers.5
Sensitivity analysis
The odds ratios (OR) estimate for current smokers for AMD used in the above calculation is a best estimate of 3.12 (95% CI 2.10 to 4.64). For ex-smokers, the best estimate OR is 1.36 (95% CI 0.97 to 1.90).1 With a ‘best estimate’ of 61,800 of AMD cases with visual impairment or blindness attributable to smoking and assuming a null effect (OR=1) of ex-smoking status and a minimum OR=2.1 for current-smoker status, the minimum number of such AMD cases attributable to smoking in the UK would be 20,000 in this age group (>69 years). Similarly, using the upper 95% CI of 4.64, for current smokers and 1.90 for ex-smokers,1 the maximum number of such attributable cases would be 92,306. As the prevalence of UK AMD estimates that we used are not gender-stratified, we also performed a sensitivity analysis, using the 95% CI intervals for the prevalence of AMD9 The minimum number of AMD cases with visual impairment or blindness caused by smoking in the UK population would be 29,500 and the maximum 92,500, against the same ‘best estimate’ of 53,900.
Potential impact of reducing smoking prevalence
To illustrate the potential impact
of a reduction in smoking in the population, we calculated the potential
number of AMD cases that could be expected if exposure to both current
and past smoking in those >69 years was halved in the future, assuming
current population structure. Such a reduction in smoking among elderly
subgroups would prevent 21,700 cases of AMD with visual impairment or blindness
independently of smoking status in future cohorts, or 40% of all attributable
cases, or 11% of all such cases. An important caveat is that this calculation
is hypothetical, and does not take into account the ‘lag’ phase between
exposure cessation and return to baseline relative risk or potential changes
in future demographics or other preventive or curative interventions.