Effect of coffee (caffeine) against human cataract blindness

Figures & data

Table 1 Cataract prevalence and caffeine consumption

Zone	Country name	Cataract incidence (% of total blindness)	Caffeine consumption (mg/day)
Zone 1	Benin	64	0
	Ghana	62.5	0
	Nigeria	50	0
	Congo	55	0
	Mali	50	0
	Togo	50	0
Zone 2	Kenya	55	2.70
	Sierra Leone	50	2.74
	Mauritania	50	2.74
	Tanzania	55	2.80
	Paraguay	40	5.47
	Niger	50	4.76
	Cameroon	50	5.47
	Guinea	50	8.22
	Vanuatu	65	8.20
	Central African Republic	55	8.20
	Tunisia	48.5	10.13
Zone 3	South Africa	55	11.00
	Morocco	49	24.65
	Oman	48.5	27.39
	Saudi Arabia	48.5	43.8
	Barbados	40	27.39
	Brazil	40	26.00
	Bulgaria	28.5	79.0
Zone 4	Turkey	28.5	10.95
	Turkmenistan	35.5	54
	Belarus	24	16
	Hungary	24	84.93
	Latvia	24	93.15
	Lithuania	24	112
	Ukraine	24	38.5
Zone 5	USA	7.6	226
	Canada	5	178
	Denmark	5	271
	Finland	5	328
	France	5	148
	Iceland	5	246
	Ireland	5	104
	Italy	5	162
	the Netherlands	5	230
	UK	5	200
	Norway	5	271
	Australia	5	202

Note: The zones labeled 1–5 represent countries in areas specified with the following WHO abbreviated names: Afr D, Afr E, Emr B and D, Eur C, and Eur A, respectively.

Abbreviation: WHO, World Health Organization.

Table 2 Zone-wise data showing decreasing incidence of cataract with increase in caffeine intake

Zone	Caffeine intake (mg/day)	Cataract incidence (%)	n
1	0	55.25±6.56 (2.66)	6
2	5.6±2.720 (0.860)	51.68±6.51 (1.93)	10
3	34.28±21.94 (8.95)	44.21±8.74 (3.56)	6
4	48.02±46.28 (18.88)	26.28±4.39 (1.79)	6
5	213.83±61.58 (19.48)	5.21±0.75 (0.23)	13

Note: The values are expressed as mean ± standard deviations and standard errors of the means.

Abbreviation: n, the number of countries in each zone.

Table 3 Intergroup t and (P) values for caffeine intake and cataract blindness

Interzone	Caffeine intake	Cataract blindness
Between 2 and 1	5.02 (0.005)	1.16 (0.23)
Between 3 and 1	3.81 (0.0034)	2.48 (0.03)
Between 4 and 1	2.54 (0.0293)	9.04 (0.0001)
Between 5 and 1	8.35 (0.0001)	16.77 (0.0001)
Between 3 and 2	4.16 (0.001)	2.12 (0.0626)
Between 4 and 2	2.96 (0.0103)	8.87 (0.0001)
Between 5 and 2	10.62 (0.001)	27.77 (0.001)
Between 4 and 3	0.662 (0.5527)	6.05 (0.001)
Between 5 and 3	6.75 (0.0001)	16.52 (0.001)
Between 5 and 4	5.84 (0.001)	17.33 (0.0001)

Notes: Data were analyzed for means, standard deviations, and errors by using routine statistical formulas. They were then further analyzed for statistical significance by Student’s t-test. The corresponding P-values were then read from standard t tables. As may be noted, all the P-values showing inhibition of cataract formation with increasing caffeine content were notably significant, except that between the zones 2 and 1.

Figure 1 Regression analysis.

Notes: The graph shows an inverse correlation between vision impairment (%) due to cataract and caffeine intake (mg/day). As may be noted, the downward correlation between caffeine intake and the cataract incidence is highly apparent with coefficient of correlation and inhibition of cataract blindness with caffeine is highly significant, with R² value approaching 8. The Spearman’s rank-order correlation coefficient and the overall P-value are −0.89 and 0.0001, respectively.