Prevalence of Skeletal Fluorosis in Northern Tanzania: A Follow-Up Study

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FIGURE 1
Flow Chart to Show Identified Cases of Skeletal Fluorosis, Tindigani, Tanzania
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FIGURE 2
Percentage per TFI Grade Split by Presence of Skeletal Fluorosis, Tindigani, Tanzania
Abbreviations: SF, skeletal fluorosis; TFI, Thylstrup and Fejerskov Index.
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FIGURE 3
Change in Fluoride Concentration of Different Drinking Water Sources Between 2009 and 2018, Tindigani, Tanzania

TABLE 1.

Age-Specific Prevalence Rates of Skeletal Fluorosis, Tindigani, Tanzania

Age Range, Years	Cases, No.	Study Population, No.	Prevalence, % (95% CI)
0–4	1	260	0.38 (0, 1.1)
5–9	7	344	2.0 (0.5, 3.5)
10–14	12	229	5.2 (2.4, 8.1)
15–19	6	84	7.1 (1.6, 12.7)
20–24	5	91	5.5 (0.8, 10.1)
25–29	5	80	6.3 (0.9, 11.6)
30–43	2	66	3.0 (0, 7.2)
35–39	0	36	0
40–44	3	31	9.7 (0, 20.1)
45–49	2	34	5.9 (0, 13.8)
50–99^{^a}	2	104	1.9 (0, 4.6)
Total	45	1359	3.3 (2.4, 4.3)

Abbreviation: CI, confidence interval.
↵a Age bands combined due to low numbers of cases in each age range. 95% confidence interval (CI) negative values rounded to 0.

TABLE 2.

Comparison Statistics Between Skeletal Fluorosis and No Skeletal Fluorosis, Tindigani, Tanzania

	Skeletal Fluorosis	No Skeletal Fluorosis	Statistical Test Used	Significance
Mean age	21.93	17.36	Mann-Whitney U	P=.001(U=2,109.5)
Male-to-female ratio	23:22	647:667	Pearson Chi-Square	P=.805(χ²=0.651)
Mean Thylstrup and Fejerskov Index grade	4.96	3.21	Mann-Whitney U	P<.001(U=5,935.5)

TABLE 3.

Comparison Between 2009 Original Prevalence Skeletal Fluorosis Study and 2018 Case Findings, Tindigani, Tanzania

Finding	2009 (n=56)	2018 (n=15)
Mean Thylstrup and Fejerskov Index grade^{^a}	6	5
Mean coronal tibiofemoral angle in worse leg with genu varus	10.17	6.16
Mean coronal tibiofemoral angle in worse leg with genu valgus	−9.47	−3
Saber tibia, no. (%)	18 (32)	0 (0)
Education affected, no. (%)	17 (30)	1 (6.6)
Unable to achieve daily tasks, no. (%)	17 (30)	3 (20)