Table 1.
Epidemiologic Studies in Nicaragua and El Salvador Examining Possible Risk Factors for Reduced Kidney Function
| Torres et al15 (2010) | Sanoff et al20 (2010) | O’Donnell et al18 (2010) | González-Quiroz22 (2011) | Laux et al17 (2012) | McClean et al23 (2012) Cross-sectional Survey | McClean et al23 (2012) Prospective Cohort | Peraza et al16 (2012) | Orantes et al19 (2011) | |
|---|---|---|---|---|---|---|---|---|---|
| Study Characteristics | |||||||||
| Design | Community-based cross-sectional survey | Screening program & nested case-control analysis | Community-based cross-sectional survey & case-control | Community-based cross-sectional survey | Community-based cross-sectional survey | Occupational cross-sectional survey | Prospective cohort (over a harvest season) | Community-based cross-sectional survey | Community-based screening & cross-sectional survey |
| Country | Nicaragua | Nicaragua | Nicaragua | Nicaragua | Nicaragua | Nicaragua | Nicaragua | El Salvador | El Salvador |
| Setting altitude & type | 4 villages at <300 masl in León/Chinandega: mining-subsistence farming, banana-sugarcane, fishing, service; 1 village at 200-675 masl: Coffee | 9 municipalities in León/Chinandega, generally in lowlands, includes sugarcane areas | 1 agricultural municipality, Quezalguaque in León; 80% with residence <500 masl | 55 communities in Chichigalpa, lowlands <300 masl, mostly sugarcane | 1 coffee village at 1,000 masl | Workers in mining, construction, & ports in lowland León/Chinandega, never worked in sugarcane | 1 sugarcane company in lowland Chinandega with distinct job titles | 5 distinct communities, 2 at sea level: both sugarcane; 3 at ≥500 masl: sugarcane, coffee, service | 3 coastal agricultural communities in the mouth of Lempa River (Bajo Lempa), at sea level |
| Study population (age, sex) | All community members, age 20-60 y, N = 1,096 (479 M/617 F) | Screening program: volunteers, age ≥ 18 y, N = 997 (848 M/149 F); Case-control: 112 cases, 222 controls, women excluded | Cross-sectional survey: weighted random sample, age ≥ 18 y, 17% of households, N = 771 (298 M/473 F); Case control: 98 cases & 221 controls from same household | Weighted random sample, age 20-60 y, N = 704 (237 M/467 F) | All community members, age 20-60 y, N = 267 (120 M/167 F) | Miners, n = 51; construction workers, n = 60; port workers, n = 53; age 18-63 y, only 3 F | Age 18-63 y, N = 284 (254 M/30 F); cane cutters, n = 51; seed cutters, n = 26; irrigators, n = 50; (re)seeders, n = 28; agrochemical applicators, n = 26; drivers, n = 41; factory workers, n = 50 | All community members, age 20-60 y, N = 674 (256 M/408 F) | 375 families (88% of community members), age > 18 y, N = 775 (343 M/432 F) |
| Community or group prevalence (%) of eGFRMDRD < 60 mL/min/1.73 m2 | Mining/subsistence farming: M 18.5/F 4.9; banana-sugarcane: M 17.1/F 4.0; fishing: M 10.5/F 2.2; service, M 0.0/F 0.0; coffee, M 7.5/F 0.0 | Volunteer population: M 14.0/F 3.4 | M 20.1/F 8.0 | M 28.3/F 2.4 | M 0.0/F 1.4 | Mining, 5.9; construction, 5.0; port work, 7.9 | All workers preharvest, 0.4 (requirement for hiring SCr ≤ 1.3 mg/dL); all workers at late harvest, 5.5; cane cutters, 5.9; seed cutters, 11.5; irrigators, 2.0; other categories, 0.0 | Sugarcane lowland, M 18.6/F 8.0; sugarcane highland, M 1.8/F 3.1; coffee, M 0.0/F 1.2; services, M 0.0/F 2.4 | M 16.9/F 4.1 |
| Urinary biomarkers of kidney function | Not studied | Not studied | Not studied | Not studied | Not studied | Increased NGAL & NAG associated with decr eGFR; IL-18 highest in miners but not associated with decr eGFR | At late harvest: NGAL, NAG, & IL-18 highest in cane/seed cutters; Incr NGAL & NAG associated with decr eGFR; increase of NGAL & IL-18 during harvest largest for cane cutters & NAG largest for cane & seed cutters | Not studied | Not studied |
| Associations of Selected Risk Factors With Decreased eGFRa | |||||||||
| Male sex | Yes | Yes | Yes | Yes | No | NA (only 3 women) | NR | Yes | Yes |
| Hypertension | Yes: men | No | Yes | Yes (NS) | No | NR | NR | Yes: women | Yes |
| Diabetes | No | No | No | Yes: women | No | No | No | Yes: women | No |
| Residence at low altitude | All excess CKD at low altitude, but service village at sea level without excess CKD | NR | Yes | NA (all lowland) | NA (all lowland) | NA (all lowland) | NA (all lowland) | Yes | NA (all lowland) |
| Family history of CKD | NR | Yes | NR | NR | NR | NR | NR | NR | Yes |
| (Illegal) alcohol | No | Yes: illegal; no: legal | Yes: legal (NS); no: illegal | No | No | No | No | No | No |
| NSAIDs | Yes: women (NS) | NR | No | No | No | NR | NR | No | No |
| Metals | Not studied | Not studied | No: lead | Not studied | Not studied | Yes: high total arsenic; no: lead, cadmium, uranium | Not studied | Not studied | |
| Associations of Agricultural Risk Factors With Decreased eGFRa | |||||||||
| Any agricultural work | Yes | Yes | No | No | No | NA | Yes | Yes | No |
| Sugarcane | Yes | NR | No | Yes | NA | NA | Yes: fieldworkers, especially cane & seed cutters | Yes: lowland; no: highland | NR |
| Cotton | NR | No | No | No | NA | NA | NA | Yes | NR |
| Coffee | No | NA | NA | NA | No | NA | NA | No | NA |
| Subsistence farming | Yes | NR | NR | NR | NR | NA | NA | Unclear | NR |
| Other crops | Yes: banana | Yes: banana, corn, rice; No: beans, sesame seed, cattle | NR | No: banana | NR | NA | NA | No | NR |
| Other jobs with heat exposure | Yes: mining, artisanal work, construction | Yes: sugar mills | NR | Yes: construction | NR | Yes: mining, construction, port work | NA | Yes: construction, service jobs | NR |
| Pesticides/ agrochemicals | NR | Yes | Yes (NS) | No | No | NA | No | NR | No |
| Heavy exertion | NR | NR | No | NR | NR | NR | Yes | NR | NR |
| High water intake | NR | Yes | No | NR | NR | No | No | NR | NR |
| Major limitations | Cross-sectional; analyses limited to current occupation | Volunteer study with likely selection bias; omission of sugarcane in the analyses | Cross-sectional; in case-control component, controls were not randomly selected from study population; no stratification by sex, obscuring work-related associations | Cross-sectional; analyses limited to current occupation | Cross-sectional; only confirms low risk in a low-risk community | Cross-sectional; no recruitment data; no multivariate analyses presented | High loss to follow-up | Cross-sectional | Cross-sectional; no stratification by sex, obscuring work-related associations; omission of sugarcane in analyses |
Note: In the prospective cohort in the McClean et al study, the largest decrease in eGFR during harvest was among cane cutters and seed cutters. Conversion factor for SCr in mg/dL to μmol/L, ×88.4.
Abbreviations: CKD, chronic kidney disease; decr, decreased; eGFR, estimated glomerular filtration rate; IL-18, interleukin 18, incr, increased; masl, meters above sea level; MDRD, Modification of Diet in Renal Disease Study equation; NA, not applicable; NGAL, neutrophil gelatinase-associated lipocalin; NR, not reported; NS, not statistically significant. NSAIDs, nonsteroidal anti-inflammatory drugs; SCr, serum creatinine.
a
Yes = positive association observed; no = no association observed.